Advanced systemic mastocytosis is a relatively rare entity where allogeneic stem cell transplantation can lead to the cure of the disease in selected patients. Delayed incomplete responses with graft‐versus‐mastocytosis effect were published in a few cases. In this particular patient's report, we describe the direct evidence and potency of graft‐versus‐mastocytosis effect of donor lymphocyte infusions in a patient with systemic mastocytosis with associated hematological neoplasm (SM‐AHN). In a 53‐year‐old female patient, an allogeneic stem cell transplantation after conventional induction treatment was performed for transformed acute myeloid leukemia (AML) during the course of polycythemia vera. After 6 years of remission period of AML and PV, the patient developed aleukemic mast cell leukemia and JAK2‐positive myeloproliferative neoplasm (SM‐AHN). We were able to achieve a sustained complete remission of SM‐AHN lasting for 6 years with only donor lymphocyte infusions in a status of mixed chimerism. The patient is in a good clinical condition and remission. The potent graft‐versus‐mastocytosis effect in this patient resembles the favorable effect of donor lymphocyte infusions in relapsing chronic myeloid leukemia patients after transplantation. This patient is, to our knowledge, the first case showing the proof of principle of graft‐versus‐mastocytosis effect.

Abstract Background: Tyrosine kinase inhibitors (TKIs) have significantly improved the treatment of CML. Even though TKI treatment is generally not considered curative, recent studies have shown that nearly half of CML patients who have achieve good and durable responses are able to stop the TKI treatment. However, patients who have successfully discontinued TKI treatment still have residual disease. We hypothesized that the immune system plays a role in treatment free remission (TFR), and our preliminary results in the EURO-SKI trial showed that patients who relapse early after imatinib discontinuation have decreased numbers and frequencies of NK cells. In EURO-SKI trial relapse was defined as the loss of major molecular response (MMR). We now aimed to analyze in more detail the phenotype and function of the NK cells in order to understand their role in TFR. Methods: Lymphocyte subclass analysis (the number of NK-, T- and B-cells) was performed at the time of therapy discontinuation and 1 month after the imatinib discontinuation in patients participating in the EURO-SKI stopping trial in the Nordic countries (n=105, results are presented from patients who have reached 6 months follow-up). More detailed immune phenotype and functional assays (NK-cell degranulation and secretion of Th1 type of cytokines IFN-γ/TNF-α) were analyzed from a proportion of patients (n=31). Results: Imatinib treated patients remaining in remission for 6 months (non-relapsing, n=48, median age 60,5 years) displayed an increased amount of NK cells at the time of drug discontinuation (18.6% vs. 11.0%, p=0.02, NK-cell count 0.25 x109 cells/L vs. 0.184 x109 cells/L m, p=0.059) compared to patients who relapsed early (before 5 months, n=29, median age 60,5 years). Furthermore, the NK cell frequency in non-relapsing patients was even higher than in healthy controls (11.5%, n=48, p=0.001). T and B cell counts and frequencies showed no differences between the groups. Detailed analysis of the NK cell compartment displayed a more mature phenotype for the NK cells in non-relapsing patients. Larger frequencies of NK cells from early relapsing patients was CD56bright compared to non-relapsing patients (4.8% vs. 2.7% of CD56 NK cells, p=0.04). Furthermore, patients who had higher frequencies of CD56bright NK cells than median had decreased TFR at 6 months (42%) compared to patients with lower frequency (70%, p=0.01). In addition, there was a trend towards more CD57pos (78% (n=21) vs. 66% (n=10), p=0.09) CD56dim NK cells in non-relapsing patients. To further study the mature NK cells in non-relapsing patients, recently identified markers (FceRgneg, PLZFneg, SYKneg, EAT-2neg) for adaptive NK cells were analyzed. Interestingly, there was a trend that non-relapsing patients had higher frequencies of adaptive-like NK cells. For example, non-relapsing patients had more CD56dim NK cells that had down regulated EAT-2 (2.8% (n=6) vs. 1.3% (n=5) of lymphocytes, p=0.03) and more CD56dim NK cells expressing NKG2D (11.2% vs. 2.6% of lymphocytes, p=0.02) and NKp46 (13.6% vs. 3.9% of lymphocytes, p=0.05). Moreover, after imatinib discontinuation the expression of transcription factor Eomes increased in the CD56dim NK cells of the early relapsing group (baseline MFI 2045 vs. 1 month 3480, p=0.06), while in non-relapsing group it seemed to even decrease (baseline MFI 2273 vs. 1 month 1980, p=0.13) pointing towards an adaptive phenotype. No significant differences between the groups were observed when degranulation against K562 cell line was studied. However, CD16neg NK cells from non-relapsing patients responded to K562 stimulation by secreting more TNFα/IFNγ compared to the early relapsing patients (21% vs. 13% of CD56pos CD16neg NK cells, p=0.01). Furthermore, patients whose CD16neg NK cells had higher than median TNFα/IFNγ secretion when stimulated with K562 cells showed an increased TFR at 6 months (78%) compared to patients who had lower TNFα/IFNγ secretion than median (37%, p=0.005). Conclusions: CML patients who successfully discontinued imatinib therapy displayed a higher number and frequency of peripheral blood mature, adaptive-like NK cells capable of secreting cytokines TNFα/IFNγ relative to relapsing patients. How such NK cells may contribute to maintenance of treatment free remission is still unknown. Nonetheless, our results warrant further clinical studies with NK-cell modulating agents. Disclosures Muller: Novartis: Honoraria, Other: Consulting or Advisory Role, Research Funding; ARIAD Pharmaceuticals Inc.: Honoraria, Other: Consulting & Advisory Role, Research Funding; BMS: Honoraria, Other: Consulting or Advisory Role, Research Funding. Hjorth-Hansen:Novartis: Honoraria; Ariad: Honoraria; Bristol-Myers Squibb: Research Funding; Pfizer: Honoraria, Research Funding. Saussele:Pfizer: Honoraria, Other: Travel grant; BMS: Honoraria, Other: Travel grant, Research Funding; Novartis Pharma: Honoraria, Other: Travel grant, Research Funding; ARIAD: Honoraria. Mahon:ARIAD: Consultancy; Novartis: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy. Porkka:Bristol-Myers Squibb: Honoraria; Celgene: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Richter:Ariad: Honoraria; Bristol-Myers Squibb: Honoraria; Novartis: Honoraria. Mustjoki:the Finnish Cancer Societies: Research Funding; Pfizer: Honoraria, Research Funding; Academy of Finland: Research Funding; Sigrid Juselius Foundation: Research Funding; Finnish Cancer Institute: Research Funding; Signe and Ane Gyllenberg Foundation: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Abstract Background: Recent reports suggest that approximately 40% of CML patients who have achieved sustained complete molecular remission are able to stop TKI treatment without disease relapse. However, there are no predictive markers for successful therapy discontinuation. Therefore, we set up an immunological sub-study in the ongoing pan-European EURO-SKI stopping study. Our aim was to identify predictive biomarkers for relapse/non-relapse and to understand more on the mechanisms of immune surveillance in CML. Methods: The EURO-SKI study started in 2012, and patients included were at least three years on TKI and at least one year in MR4 or deeper before the study entry. Basic lymphocyte immunophenotyping (the number of NK-, T- and B-cells) was performed at the time of therapy discontinuation and 1, 6, and 12 months after the TKI stop and in case of relapse (defined as loss of MMR, BCR-ABL1>0.1% IS). In addition, from a proportion of patients more detailed immunophenotypic and functional analyses (cytotoxicity of NK-cells and secretion of Th1 type of cytokines IFN-γ/TNF-α) were done at the same times. Results: Thus far 119 Nordic patients (imatinib n=105, dasatinib n=12, nilotinib n=2) who have discontinued TKI treatment within the EURO-SKI study have been included in the lymphocyte subclass analysis (results are presented from patients who have reached 6 months follow-up). Immunophenotyping analysis demonstrates that imatinib treated patients who were able to maintain remission for 6 months (n=36) had increased NK-cell counts (0.26 vs. 0.15x109cells/L, p=0.01, NK-cell proportion 18.9% vs. 11%, p=0.005) at the time of drug discontinuation compared to patients who relapsed early (before 5 months n=22). Furthermore, the phenotype of NK-cells was more cytotoxic (more CD57+ and CD16+cells and less CD62L+cells), and also their IFN-γ/TNF-α secretion was enhanced (19.2% vs. 13%, p=0.02). Surprisingly, patients who relapsed more slowly (after 5 months, n=16) had similar baseline NK-cell counts (0.37x109cells/L), NK-cell proportion (21.2%), and phenotype and function as patients, who were able to stay in remission. No differences in the NK-cell counts were observed between patients who had detectable or undetectable BCR-ABL1 transcripts at the baseline (0.22 x109cells/L vs. 0.31 x109cells/L, p=0.61). Interestingly, NK-cell count was higher in patients with low Sokal risk score than in patients with intermediate risk (0.33 x109cells/L vs. 0.20 x109cells/L, p=0.04). Furthermore, there was a trend that male patients had a higher proportion of NK-cells than females (21.6% vs. 15.7%, p=0.06). Pretreatment with IFN-α or the duration of imatinib treatment did not have an effect on NK-cell count or proportion. In comparison to the imatinib group, dasatinib treated patients had higher NK-cell counts at the baseline (median 0.52x109cells/L vs. 0.26x109cells/L, p=0.02), and also the proportion of CD27 (median 50% vs. 16%, p=0.01) and CD57 expressing (median 79% vs. 74%, p=0.05) NK-cells was higher. The follow-up time of dasatinib treated patients is not yet long enough to correlate the NK-cell counts with the success of the treatment discontinuation. The absolute number of T-cells or their function did not differ significantly between relapsing and non-relapsing patients at the time of treatment discontinuation. However, both CD4+ and CD8+ T-cells tended to be more mature in patients who stayed in remission compared to patients who relapsed early (CD4+CD57+CD62L- median 5.7% vs. 2.4%, p=0.06, CD8+CD62L+CD45RA+ 13% vs. 26.7%, p=0.05). The analysis of follow-up samples showed that in patients who stayed in remission the Th1 type cytokine (IFN-γ/TNF-α) secretion of CD8+T-cells increased at 6 months compared to baseline (23.6 vs. 18.5%, p=0.07). Same phenomenon was observed in the late relapsing group at relapse compared to baseline (37.9 vs. 13.5%, p=0.03). No similar increase was observed in the early relapsing group. Conclusions: Low NK-cell numbers and poor cytokine secretion may predict early disease relapse after TKI discontinuation. However, patients who relapse later have high numbers of normally functioning NK-cells. Further research (detailed phenotypic analysis of NK- and T-cells including activating and inhibitory receptors and immune checkpoint molecules) and correlation of biomarker data with clinical parameters are ongoing to understand the ultimate determining factors of relapse. Disclosures Själander: Novartis: Honoraria. Hjorth-Hansen:Novartis: Honoraria; Bristol-myers Squibb: Honoraria; Ariad: Honoraria; Pfizer: Honoraria. Porkka:BMS: Honoraria; BMS: Research Funding; Novartis: Honoraria; Novartis: Research Funding; Pfizer: Research Funding. Mustjoki:Bristol-Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Abstract Background The inhibition of oncogenic BCR-ABL1 kinase with tyrosine kinase inhibitors (TKIs) has significantly improved the prognosis of CML. Recent reports suggest that approximately 40 % of CML patients who have achieved optimal therapy response (complete molecular remission, CMR) can stop imatinib treatment without recurrence of detectable BCR-ABL1 transcripts. However, no predictive prognostic factors for successful therapy discontinuation have yet been identified. We therefore set up an immunological substudy in the ongoing pan-European EURO-SKI stopping study. We aimed to identify predictive biomarkers for relapse and non-relapse after TKI discontinuation. In addition, we aimed to understand more on the mechanisms of immune surveillance in CML and to study the effects of TKI treatment on the immune system. Materials and methods Patients in deep molecular remission (MR4, BCR-ABL < 0,01% IS) for at least one year and with TKI treatment for at least 3 years were eligible for the clinical study. Basic lymphocyte immunophenotyping (the proportions and absolute numbers of NK-, T- and B-cells) was performed at the university hospital laboratories at the time of therapy discontinuation, and 1, 6, and 12 months after the TKI discontinuation. In a proportion of patients a more detailed immunophenotypic (analysis of CD45RA, CD57, CD27 and CD62L expressions) and functional analyses were done from fresh blood samples in a central immunology laboratory (Helsinki) at the same time points. The cytotoxicity of NK-cells was studied by measuring the direct killing of target cells (K562) and by the degranulation assay (CD107a/b expression). The secretion of Th1 type of cytokines IFN-γ/TNF-α was studied from both T- and NK-cells. Results Thus far the basic lymphocyte subclass measurement has been analyzed from 62 patients who have discontinued TKI treatment within the EURO-SKI study. Functional analyses have been performed from 30 patients. 60 patients have used imatinib before treatment discontinuation and 2 patients dasatinib. At baseline, before the treatment discontinuation both CD4+ and CD8+ T-cell counts were within the normal range (median CD4+ 0.73x 109/L, range 0.11-2.4x 109/L; CD8+ 0.35x 109/L, 0.07-1.92 x 109/L). The TKI stop had no significant numerical or functional effect on T-cells, and at 1 month time-point the median T-cell counts were unchanged (CD4+ 0.73x 109/L; CD8+ 0.35x 109/L). Similarly, at the baseline, the median NK-cell count was within a normal range (0.26 x 109/L, range 0.04-1.04 x 109/L), and no significant change was observed 1 month after stopping the treatment (median 0.29 x 109/L). Furthermore, at the baseline and at the 1-month time-point the cytotoxicity of NK-cells and the cytokine secretion of T- and NK-cells did not significantly differ from the healthy controls when all patients were considered as a one group. However, when patients were divided in two groups based on the relapse status, the patients who eventually relapsed had significantly fewer NK-cells already at the baseline (Figure A; absolute count 0.18x 109/L vs. 0.32 109/L, p=0.008; proportions 11% vs. 21%, p=0.001). The phenotype of NK-cells also differed between the two groups, and the patients who relapsed had less NK-cells expressing CD57 (median 58% vs. 69%, p=0.046) and CD16 (median 67% vs. 83%, p=0.018) on the cell surface. Furthermore, the cytotoxicity of NK-cells was impaired in patients who failed to discontinue the TKI treatment successfully and no killing activity was observed in their samples (Figure B; alive K652 cells after co-incubation with effector cells 100% vs. 88%, p=0.07). No clear differences were observed in the function or the numbers of T-cells between relapsing and non-relapsing patients. Conclusions The NK-cell numbers and their function may predict disease relapse after TKI discontinuation. This may have impact on the future stopping trials. In addition, it further illustrates the importance of the immune system in the successful long-term treatment of CML. Disclosures: Ekblom: Novartis: Honoraria; Bristol-Myers Squibb: Honoraria. Hjorth-Hansen:Pfizer, BMS: Honoraria, Travel expenses Other. Porkka:BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Richter:Bristol-Myers Squibb: Consultancy, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau. Mustjoki:Novartis: Honoraria; BMS: Honoraria, Research Funding.

Abstract Background Dasatinib is a potent BCR-ABL1 and SRC tyrosine kinase inhibitor, which in vitro is more effective against progenitor and putative leukemia stem cells than imatinib. This may translate into deeper molecular responses in vivo. Methods We randomized (1:1) 46 newly diagnosed CML patients to receive dasatinib 100 mg or imatinib 400 mg once daily. The primary endpoint of our study was treatment response in stem and progenitor cell fractions (Mustjoki et al, Leukemia 2013). We here summarize the clinical results of the study after a 24-month follow-up focusing on toxicity and standard response evaluation by quantitative BCR-ABL1 PCR and cytogenetics (NCT00852566 www.ClinicalTrials.gov). Results Both imatinib and dasatinib treated patients fared well with deeper and faster treatment responses than what has been reported in the registration studies. By karyotyping, dasatinib induced a faster response by 3 months (median of 5% of Ph+ cells in imatinib group vs. 0% in dasatinib group, p=0.01, n=21 in each group), but already by 12 months the difference disappeared, as all evaluable patients were in complete cytogenetic remission. The rate of molecular response MR3.0 was already at the 3 months time-point better in the dasatinib group (36% vs 8%, p=0.02; see Table), but within 18 months imatinib patients caught up the difference. In contrast, the achievement of deeper therapy responses, MR4.0 and MR4.5, was clearly different between the groups and increased over 24 months. After 18 months 64% and 71% of imatinib- and dasatinib-treated patients had achieved MR3.0 (p=0.59), while the MR4.0 rates were 23% and 62% (p=0.009) and MR4.5 rates 4% and 41% (0.003) (see Table below). The difference in median transcript levels was approximately 1 log (>10-fold difference) in all time-points after 3 months of therapy (see Table below). A total of 7 patients (30%) in both groups discontinued assigned treatment. Main drug-related toxicities were as expected. Dasatinib-induced serosal inflammation (pleural/pericardial effusions) was more frequent than in registration studies (6 patients, 27%). In 4 patients (18%) this led to therapy discontinuation, despite of drug interruption and dose reductions. In the imatinib group 3 patients discontinued due to drug-related toxicity (liver toxicity, rash and severe hypogammaglobulinemia with recurrent infections). Disease progression occurred in one dasatinib-treated patient (cytogenetic progression with the appearance of V299L mutation at month 9) and two imatinib-treated patients (blastic transformation at month 2 and molecular progression at month 18). The patient in blast phase has been transplanted and is currently in molecular remission. No CML-related deaths occurred, but one patient died from lung cancer. Interpretation Dasatinib induced faster and deeper molecular responses than imatinib and overall responses were better in both groups than in the registration studies. Relatively high rate of serosal toxicity was observed among the dasatinib-treated patients, but this had no adverse effect on response. Upcoming studies will show if the deeper treatment responses induced by dasatinib therapy translate into increased probability of successful therapy discontinuation. Disclosures: Hjorth-Hansen: Pfizer: Honoraria, Travel, Travel Other; Bristol-Myers Squibb: Honoraria, Research Funding, Travel, Travel Other; Novartis: Honoraria, Travel Other; Merck: Research Funding. Richter:Novartis: Consultancy, Honoraria, Research Funding, Travel Other; Bristol-Myers Squibb: Consultancy, Honoraria, Travel, Travel Other. Porkka:BMS: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau. Mustjoki:Novartis: Honoraria; BMS: Honoraria, Research Funding.

Clinical management guidelines on malignant disorders are generally based on data from clinical trials with selected patient cohorts. In Sweden, more than 95% of all patients diagnosed with chronic myeloid leukemia (CML) are reported to the national CML registry, providing unique possibilities to compile population-based information. This report is based on registry data from 2002 to 2010, when a total of 779 patients (425 men, 354 women; median age, 60 years) were diagnosed with CML (93% chronic, 5% accelerated, and 2% blastic phase) corresponding to an annual incidence of 0.9/100,000. In 2002, approximately half of the patients received a tyrosine kinase inhibitor as initial therapy, a proportion that increased to 94% for younger (<70 years) and 79% for older (>80 years) patients during 2007-2009. With a median follow-up of 61 months, the relative survival at 5 years was close to 1.0 for patients younger than 60 years and 0.9 for those aged 60 to 80 years, but only 0.6 for those older than 80 years. At 12 months, 3% had progressed to accelerated or blastic phase. Sokal, but not European Treatment and Outcome Study, high-risk scores were significantly linked to inferior overall and relative survival. Patients living in university vs nonuniversity catchment areas more often received tyrosine kinase inhibitors up front but showed comparable survival.

Thirty-eight adult patients with chronic lymphocytic leukemia (CLL) underwent reduced-intensity conditioning (RIC) allogeneic stem cell transplant (allo-SCT) in Sweden between 1999 and 2007. The cumulative incidences of acute graft-versus-host disease (GVHD) grades II-IV and chronic GVHD were 29% and 47%, respectively. Rates of non-relapse mortality, progression-free survival (PFS) and overall survival (OS) were 18%, 47% and 74% at 1 year, and 21%, 25% and 45% at 5 years, respectively. T-cell chimerism after transplant was measured in 31 out of 34 patients (91%) surviving beyond day +100. Seventeen patients achieved >90% donor T-cell engraftment at 3 months after allo-SCT and, compared with the 12 patients with ≤90% donor T-cell engraftment, they showed favorable PFS at 1 year (82% vs. 33%, p =0.002) and better long-term PFS and OS (p =0.002 and 0.046, respectively). Donor T-cell engraftment of >90% at 3 months after RIC allo-SCT for CLL seems to predict favorable short-term and long-term outcome.

Long-term survival after allogeneic stem cell transplantation for relapsed large B cell lymphomas : a retrospective study

Reduced‐intensity conditioning ( RIC )‐allo SCT is increasingly used for acute myelogenous leukemia. Limited data are available for the comparison of peripheral blood stem cells with bone marrow for RIC ‐allo SCT . We used the E uropean G roup for B lood and M arrow T ransplantation ( EBMT ) ALWP data to compare the outcome of mobilized peripheral blood stem cells ( PBSC ) ( n = 1430) vs. bone marrow ( BM ) ( n = 107) for acute myelogenous leukemia ( AML ) patients with complete remission that underwent RIC ‐allo SCT from compatible sibling donors. The leukemia features, the disease status, and the time from diagnosis were similar between the two groups. Engraftment was achieved in 99% and 93% in the PBSC and BM groups, respectively ( P < 0.0001). The day of engraftment was significantly earlier for the PBSC vs. the BM group, 15 (1–59) and 19 (5–69), respectively ( P < 0.001). Acute GVHD , severe GVHD (grade III–IV) and chronic GVHD did not differ between the groups. leukemia‐free survival ( LFS ), relapse, and non‐relapsed mortality ( NRM ) were 51 ± 2%, 32 ± 1%, and 17 ± 1% vs. 50 ± 6%, 38 ± 6%, and 12 ± 3% for the PBSC and BM groups, respectively. Our results indicate faster engraftment, but no difference in GVHD , LFS , relapse, and NRM when comparing PBSC to BM grafts from sibling donors following RIC conditioning. This is the first study comparing PBSC to BM grafts in the RIC setting, analyzing a homogeneous population of patients with AML in remission. Whether PBSC should be preferred for advanced phases of the disease, where the outcome is dominated by relapse incidences, needs further investigation.

This report investigated the impact of graft-versus-host disease (GVHD) on transplantation outcomes in 1859 acute myeloid leukemia patients given allogeneic peripheral blood stem cells after reduced-intensity conditioning (RIC allo-SCT). Grade I acute GVHD was associated with a lower risk of relapse (hazards ratio (HR)=0.7, P =0.02) translating into a trend for better overall survival (OS; HR=1.3; P =0.07). Grade II acute GVHD had no net impact on OS, while grade III–IV acute GVHD was associated with a worse OS (HR=0.4, P <0.0.001) owing to high risk of nonrelapse mortality (NRM; HR=5.2, P <0.0001). In time-dependent multivariate Cox analyses, limited chronic GVHD tended to be associated with a lower risk of relapse (HR=0.72; P =0.07) translating into a better OS (HR=1.8; P <0.001), while extensive chronic GVHD was associated with a lower risk of relapse (HR=0.65; P =0.02) but also with higher NRM (HR=3.5; P <0.001) and thus had no net impact on OS. In-vivo T-cell depletion with antithymocyte globulin (ATG) or alemtuzumab was successful at preventing extensive chronic GVHD ( P <0.001), but without improving OS for ATG and even with worsening OS for alemtuzumab (HR=0.65; P =0.001). These results highlight the role of the immune-mediated graft-versus-leukemia effect in the RIC allo-SCT setting, but also the need for improving the prevention and treatment of severe GVHD.

PURPOSE:Patients with myeloproliferative neoplasms (MPNs), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis, have a propensity to develop acute myeloid leukemia (AML) and myelodysplastic syndromes (MDSs). Using population-based data from Sweden, we assessed the role of MPN treatment and subsequent AML/MDS risk with special focus on the leukemogenic potential of hydroxyurea (HU).METHODS:On the basis of a nationwide MPN cohort (N = 11,039), we conducted a nested case-control study, including 162 patients (153 and nine with subsequent AML and MDS diagnosis, respectively) and 242 matched controls. We obtained clinical and MPN treatment data for all patients. Using logistic regression, we calculated odds ratios (ORs) as measures of AML/MDS risk.RESULTS:Forty-one (25%) of 162 patients with MPNs with AML/MDS development were never exposed to alkylating agents, radioactive phosphorous (P(32)), or HU. Compared with patients with who were not exposed to HU, the ORs for 1 to 499 g, 500 to 999 g, more than 1,000 g of HU were 1.5 (95% CI, 0.6 to 2.4), 1.4 (95% CI, 0.6 to 3.4), and 1.3 (95% CI, 0.5 to 3.3), respectively, for AML/MDS development (not significant). Patients with MPNs who received P(32) greater than 1,000 MBq and alkylators greater than 1 g had a 4.6-fold (95% CI, 2.1 to 9.8; P = .002) and 3.4-fold (95% CI, 1.1 to 10.6; P = .015) increased risk of AML/MDS, respectively. Patients receiving two or more cytoreductive treatments had a 2.9-fold (95% CI, 1.4 to 5.9) increased risk of transformation.CONCLUSION:The risk of AML/MDS development after MPN diagnosis was significantly associated with high exposures of P(32) and alkylators but not with HU treatment. Twenty-five percent of patients with MPNs who developed AML/MDS were not exposed to cytotoxic therapy, supporting a major role for nontreatment-related factors.

Between 1982 and 2009 a total of 92 patients with myelofibrosis (MF) in chronic phase underwent allo-SCT in nine Nordic transplant centers. Myeloablative conditioning (MAC) was given to 40 patients, and reduced intensity conditioning (RIC) was used in 52 patients. The mean age in the two groups at transplantation was 46±12 and 55±8 years, respectively (P<0.001). When adjustment for age differences was made, the survival of the patients treated with RIC was significantly better (P=0.003). Among the RIC patients, the survival was significantly (P=0.003) better for the patients with age <60 years (a 10-year survival close to 80%) than for the older patients. The type of stem cell donor did not significantly affect the survival. No significant difference was found in TRM at 100 days between the MAC- and the RIC-treated patients. The probability of survival at 5 years was 49% for the MAC-treated patients and 59% in the RIC group (P=0.125). Patients treated with RIC experienced significantly less aGVHD compared with patients treated with MAC (P<0.001). The OS at 5 years was 70, 59 and 41% for patients with Lille score 0, 1 and 2, respectively (P=0.038, when age adjustment was made). Twenty-one percent of the patients in the RIC group were given donor lymphocyte infusion because of incomplete donor chimerism, compared with none of the MAC-treated patients (P<0.002). Nine percent of the patients needed a second transplant because of graft failure, progressive disease or transformation to AML, with no significant difference between the groups. Our conclusions are (1) allo-SCT performed with RIC gives a better survival compared with MAC. (2) age over 60 years is strongly related to a worse outcome and (3) patients with higher Lille score had a shorter survival.

Abstract Abstract 784 Background: In vitro studies have suggested that CML stem cells are resistant to tyrosine kinase inhibitors (TKIs), but in vivo effects in patients have not been prospectively assessed. Furthermore, the inter-individual variation of the leukemic stem cell pool at diagnosis and its possible prognostic value is unknown. Patients: 46 newly diagnosed CML-CP patients were randomized 1:1 to receive either dasatinib 100 mg or imatinib 400 mg QD. The primary endpoint was a comparison of the proportion of Ph+ cells in CD34+CD38− and CD34+CD38+ compartment at 6 months between the study arms. Key secondary endpoints were the fraction of Ph+ cells in the stem cell compartments at 1 and 3 months, and molecular and cytogenetic responses at 3, 6, 12 and 18 months. Experimental endpoints included the percentage of Ph+ cells in the stem cell compartment at diagnosis and its correlation with therapeutic response. Results: One patient in the imatinib arm and none in the dasatinib arm progressed to blast crisis within first 12 months. 4/22 of dasatinib patients have discontinued the treatment due to side-effects (mainly pleural effusion) and 1 patient due to insufficient response. 3/24 imatinib patients have discontinued the therapy (1 blast crisis, 1 side-effects, 1 other malignancy). Early cytogenetic responses were superior in the dasatinib arm: the median percentage of Ph+ cells in the bone marrow was 81% (imatinib) vs. 70% (dasatinib) at 1 month (p=0.15) and 5% vs. 0% at 3 months (p=0.0085). At 12 months all dasatinib (n=20) and 19/20 imatinib patients were in CCyR (results based on patients on treatment at 12 months). MMR rate was significantly higher in the dasatinib arm already at 6 months (70% vs. 20%, p=0.002) and similarly at 9 (75 vs. 26%, p=0.004) and 12 months (88% vs. 40%, p=0.009). Undetectable BCR-ABL1 transcripts (at least CMR4) were observed in 20% of the dasatinib patients at 6 months compared to none in the imatinib arm (p=0.11) and 44% in the dasatinib arm at 12 months compared to 7% in the imatinib arm (p=0.037). The median percentage of Ph+ cells, as measured by FISH (1000 cells analyzed), in the CD34+CD38− fraction at diagnosis was 79% (range 1–100%) compared to 96% (range 50–100%) in CD34+CD38+ fraction. The proportion of Ph+ cells in CD34+CD38− fraction correlated with WBC count (r=0.50, p<0.001), splenomegaly (r=0.43, p=0.0055), anemia (r=-0.44, p=0.004) and blood blast percentage (r=0.57, p=0.0001) at diagnosis. There was also a significant correlation between Ph+ cells in CD34+CD38− fraction at diagnosis and cytogenetic response at 1 (r=0.63, p<0.0001), 3 (r=0.48, p=0.0025) and 6 months (r=0.36, p=0.0271). Furthermore, leukemic stem cell burden at diagnosis correlated significantly with BCR-ABL1 transcript levels at 3 (r=0.54, p=0.0005), 6 (r=0.42, p=0.0088) and 9 months (r=0.40, p=0.0123). All patients who were not in MMR at 18 months, had >79% of Ph+ cells in CD34+CD38− fraction at diagnosis. During TKI therapy, the proportion of Ph+ cells decreased rapidly in the stem cell fractions. At 1 month, the median proportion of Ph+ cells was 14% and 56% in CD34+CD38− and CD34+CD38+ fractions compared to 69% in whole BM (p<0.0001, n=38). At 3 months, the respective numbers were 0.40%, 0.20% and 0.80% (p=0.087, n=33) and at 6 months 0%, 0% and 0.1% (p=0.23, n=41). Dasatinib-treated patients had significantly lower proportion of Ph+ cells in CD34+CD38+ fraction at 3 months than imatinib patients (0.05% vs. 0.68%, p=0.0318). A similar trend was also observed at 1 month (24% vs. 69%, p=0.05), but no difference existed at 6 months. In CD34+CD38− fraction the proportions of Ph+ cells did not differ significantly at 1 (11 vs. 17%, p=0.91), 3 (0.2 vs. 0.3%, p=0.44) or 6 months (0 vs. 0%, p=0.75). Conclusions: In comparison to imatinib, dasatinib induced superior therapeutic responses with remarkably high MMR and CMR rates. This was associated with a faster reduction of Ph+ cells at the progenitor CD34+CD38+ cell level. Surprisingly, both drugs rapidly depleted Ph+ cells from the more primitive CD34+CD38− compartment. The proportion of Ph+ stem cells at diagnosis varied significantly among individual patients and bore prognostic value. Patients with a low proportion of Ph+ leukemic stem cells at diagnosis achieved faster and better cytogenetic and molecular responses. The leukemic stem cell burden at diagnosis may be a biomarker predicting treatment outcome and reflecting key biological factors in CML. Disclosures: Mustjoki: Novartis: Honoraria; Bristol-Myers Squibb: Honoraria. Richter:Novartis: Honoraria; Bristol-Myers Squibb: Honoraria. Dybedal:Novartis: Travel support. Fioretos:Cantargia AB: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Qlucore AB: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Weiss Bjerrum:Novartis: Consultancy; Bristol-Myers Squibb: Consultancy. Simonsson:Novartis, BMS, Merck, Pfizer: Consultancy, Honoraria. Porkka:Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding. Hjorth-Hansen:Novartis: Honoraria; Bristol-Myers Squibb: Honoraria.

Abstract 321 This icon denotes a clinically relevant abstract

Biologic and clinical observations suggest that combining imatinib with IFN-α may improve treatment outcome in chronic myeloid leukemia (CML). We randomized newly diagnosed chronic-phase CML patients with a low or intermediate Sokal risk score and in imatinib-induced complete hematologic remission either to receive a combination of pegylated IFN-α2b (Peg-IFN-α2b) 50 μg weekly and imatinib 400 mg daily (n = 56) or to receive imatinib 400 mg daily monotherapy (n = 56). The primary endpoint was the major molecular response (MMR) rate at 12 months after randomization. In both arms, 4 patients (7%) discontinued imatinib treatment (1 because of blastic transformation in imatinib arm). In addition, in the combination arm, 34 patients (61%) discontinued Peg-IFN-α2b, most because of toxicity. The MMR rate at 12 months was significantly higher in the imatinib plus Peg-IFN-α2b arm (82%) compared with the imatinib monotherapy arm (54%; intention-to-treat, P = .002). The MMR rate increased with the duration of Peg-IFN-α2b treatment (< 12-week MMR rate 67%, > 12-week MMR rate 91%). Thus, the addition of even relatively short periods of Peg-IFN-α2b to imatinib markedly increased the MMR rate at 12 months of therapy. Lower doses of Peg-IFN-α2b may enhance tolerability while retaining efficacy and could be considered in future protocols with curative intent.

The World Health Organization from 2008 classifies B- or T-cell lymphoblastic leukemia/lymphoma as a precursor lymphoid neoplasm [1]. Conventionally, when a lymph node mass is present and 25% or more of the nucleated cells in the bone marrow are lymphoblasts, a diagnosis of lymphoblastic leukemia is preferred to lymphoblastic lymphoma. Data about the patients (≥16 years of age), who had undergone allogeneic stem cell transplantation (ASCT) due to T- and B-cell lymphoblastic lymphoma (LBL) in Sweden, were collected from patient files, local registries, and the The European Group for blood and marrow transplantation (EBMT) data base in all participating centers (Stockholm, Gothenburg, Lund, Linköping, Uppsala, and Umeå). Nineteen patients were transplanted in four Swedish centers (Stockholm, Uppsala, Lund, and Gothenburg) between August 1987 and February 2005. A patient who underwent syngeneic stem cell transplantation and two others who were transplanted with reduced intensity conditioning regimens were excluded from this study. All the patients had a lymph node biopsy-proven histologic diagnosis of a precursor B or T lymphoblastic lymphoma. The cut-off value of 30% for blast cells in the bone marrow was used for distinguishing between leukemia and lymphoma, because the majority of patients were diagnosed before 2004. The study protocol was approved by the Regional Ethical Review Board in Gothenburg and the patients gave their informed consent before transplantation. They were treated according to different chemotherapy protocols (Wollner protocol, NOPHO, HD Ara-C and Mitoxantrone, Riehm, HyperCVAD, DexaBEAM, Swedish National therapy program for adult ALL, and Norwegian national program for ALL). Decisions about the transplantations were made, respectively, at the transplantation centers. Among the patients in complete remission (CR), only one patient was transplanted in CR2. human leurocyte antigen (HLA)-identical related donors were used in 14 patients (73%), HLA-A, B, and Dr locus (DR) identical unrelated donors were used in four patients (23%) and mismatched unrelated in one patient (4%). Other initial patient characteristics are shown in detail in Table I. Probabilities of overall survival and relapse-free survival were estimated using Kaplan–Meier method and compared with the log-rank test [2]. The incidence of graft versus hoct disease (GVHD), transplantation related mortality (TRM), and relapse were estimated using a cumulative incidence curves estimator [3]. All the tests were two sided. Analyses were performed using a cmprsk package (developed by Gray, June 2001), Splus 6.2 software (S-plus 6.2, Insightful, Seattle, WA) and Statistica software (Statistica, StatSoft, Tulsa, OK). Transplantation outcome of the 19 patients is presented in Table I. Acute GVHD Grades II–IV developed in six patients with a cumulative incidence of 32%. The incidence of acute GVHD was higher in patients who received peripheral-blood stem cells (PBSC) than bone marrow (BM) (67% vs. 15%; P = 0.02). Chronic GVHD developed in 4/16 patients with a cumulative incidence of 25% within 2 years. The cumulative incidence of TRM at 1 and 3 years was 32%. The incidence of TRM was higher in the unrelated donor transplants than in the sibling transplants (80% vs. 14%, P = 0.002) and in T- compared with B-LBL (42% vs. 0%; P = 0.06, ns). The cumulative incidence of relapse was 42%. The incidence of relapse was higher in the patients with >1 year between diagnosis and ASCT than in the patients with ASCT <1 year after diagnosis (71% vs. 25%, P = 0.06, ns). The 5-year overall survival (OS) and the progression-free survival (PFS) were 30% and 32%, respectively. The OS and PFS were longer in the patients who were transplanted <1 year after the diagnosis versus patients transplanted >1 year after diagnosis (P = 0.06, ns). There are not many reports of the results of allogeneic stem cell transplantation for lymphoblastic lymphoma in the literature. We report the results of the patients who were transplanted at the time when lymphoblastic lymphoma was treated predominantly as high-grade lymphoma rather than ALL. All the patients were transplanted in chemosensitive disease, most in CR1 and with myeloablative conditioning regimen, preferentially with cyclophosphamide and TBI. The incidence of acute and chronic GVHD does not differ significantly from that of other studies done in similar circumstances. The high incidence of TRM, especially in the matched unrelated donor (MUD) transplants, and the high relapse risk (42%) contribute to low PFS and OS. The results of our study are comparable to previous studies in lymphoblastic lymphoma [4-6]. The PFS and OS were almost identical to the previous report of the Swedish ALL group [7]. However, our study shows better results for the patients transplanted <1 year after the diagnosis compared with those transplanted >1 year after diagnosis. A year after transplant, the survival curve reaches plateau. To analyze whether there was a time related outcome improvement, we divided the patients into two groups: those transplanted between 1987 and 1998 and those transplanted between 1998 and 2005. Surprisingly, the group transplanted between 1987 and 1998 had a significantly superior PFSand OS compared with later transplants (P = 0.01) (Fig. 1). Upon a closer look at the two groups we noticed that most of the patients (91%) transplanted before 1998 were transplanted <1 year after the diagnosis. Only 25% of the patients transplanted after 1998 were transplanted a year or longer after the diagnosis (Table I). The patients transplanted between 1987 and 1998 had received less chemotherapy before the transplantation. Another contributor to the better results of this group may be the fact that more patients were in CR at ASCT and that fewer received PBSC than in the other group. The use of PBSC led to more acute GVHD and higher TRM. Furthermore, among those transplanted between 1998 and 2005, more patients had unrelated donors. In this group, there were significantly more acute GVHD and TRM compared with that of the matched related donors. Although this group is profoundly heterogeneous, this retrospective analysis confirms that a selection of patients and donors plays a crucial role for the outcome. We have shown that myeloablative allogeneic stem cell transplantation for lymphoblastic lymphoma led to a long-term survival in a third of the patients. Finally, when the transplantation was done <1 year after the diagnosis in CR, using matched sibling donors and BM as a stem cell source, with fewer chemotherapy cycles before the transplant, better results for ASCT were achieved. Overall survival after myeloablative conditioning and ASCT in 19 patients with lymphoblastic lymphoma transplanted (1987–1998) and (1999–2005). Vladimir Lj Lazarevic*, Mats Remberger*, Hans Hägglund*, Helene Hallböök*, Gunnar Juliusson*, Eva Kimby*, Claes Malm*, Anders Wahlin*, Hamdy Omar*, Jan-Erik Johansson*, * Department of HematologyUniversity Hospital LundLund University, Lund, Sweden.