Abstract Abstract 3514 Isocitrate dehydrogenase (IDH) is a metabolic enzyme that catalyzes a reaction in the tricarboxylic acid cycle. Gain of function mutations in the IDH1/2 genes have been reported in different malignancies and are observed in 15–30% of de novo AML with association to a normal karyotype and to NPM1 mutations. The exact role of IDH1/2 mutations in leukemogenesis remains to be determined. IDH mutations have not previously been studied in a cohort of therapy-related myelodysplasia (t-MDS) and therapy-related acute myeloid leukemia (t-AML). To evaluate the frequency of IDH1/2 mutations in t-MDS and t-AML, and their possible association to type of previous therapy and to other genetic abnormalities, DNA from 140 well-characterized patients with t-MDS (n=89) and t-AML (n=51) were analyzed with high-resolution melting followed by sequencing. All patients have previously been examined cytogenetically and investigated for mutations in 12 other genes: FLT3(ITD, TKD), KIT, JAK2, KRAS, NRAS, BRAF, PTPN11, RUNX1, MLL(ITD), CEBPA, NPM1, and TP53. In total, IDH mutations were detected in 12 of 140 patients (9%). 3 patients had a mutation in IDH1 and 9 patients had a mutation in IDH2 (Table 1), all mutations previously reported in de novo AML. No patients had concurrent IDH1 and IDH2 mutations. IDH mutations were not related to previous therapy with alkylating agents, topoisomerase II inhibitors or radiotherapy, but were significantly associated with other types of therapy not firmly established to be leukemogenic (p=0.004). The latency period to development of t-MDS/t-AML was not different between IDH1/2 positive (+) cases and cases with IDH (wt) (64 and 48 months, respectively, p=0.118). 4/5 cases with t-MDS and IDH+ progressed to AML compared to 27/84 t-MDS cases with IDHwt (p=0.048).Table 1:Characteristics of 12 patients with t-MDS/t-AML and mutations in IDH1/2CaseAge/sext-AML/t-MDSPrevious therapyKaryotypeOther mutationsIDH Mutation1974/FAMLAlk45,XX,-7/48,XX,der(1;7)(q10;p10),+11, +13/46,XX–IDH1 R132G2963/FAMLRT46, XXNPM1 FLT3-ITDIDH1 R132G3663/FAMLAlk46,XX,+2,+8/47,XX,der(6)t(1;6) (q?25;p21),+8N-RASIDH2 R172K4472/MMDSAlk46,XY,+1,der(1;7)(q10;p10)/46,XY–IDH2 R140Q5562/FMDS→AMLRT46, XXRUNX1IDH2 R140L7272/FMDS→AMLAlk, T II, RT46,XX,+1,der(1;7)(q10;p10)/50,XX,idem, +8,+9,14+21RUNX1IDH2 R140Q8178/MMDS→AMLAlk46,XY,der(17)t(11;17)(q13;p13),i(13) (q10)/47,idem,+der(13)t(11;13) (q13;p11)IDH2 R172K10443/FMDS→AMLAlk47,XX,+1,der(1;7)(q10;p10),+8RUNX1IDH1 R132C10944/FAMLMtx, Aza46, XXIDH2 R140Q11952/FAMLAlk, T II, RT46, XXNPM1IDH2 R140Q13325/MAMLVCR, MTX, Asp,6-MP46, XXIDH2 R140Q18060/MMDS→AMLMtx46, XXMLL-ITDIDH2 R140Q6-MP, 6 mercaptopurine; Alk, alkylating agent; Asp, l-asparaginase; Aza, azathioprine; Mtx, methotrexate; RT, radiotherapy, T II, topoisomerase inhibitor, VCR, vincristine. IDH mutations were significantly associated with a normal karyotype (6/12 cases with IDH+ vs. 18/128 with IDHwt, p=0.006) and der(1;7)(q10;p10) resulting in trisomi 1q and loss of 7q (4/12 cases with IDH+ vs. 7/128 with IDHwt, p=0.008), but was inversely correlated to other chromosome 7 abnormalities (1/12 cases with IDH+ vs. 54/128 with IDHwt, p=0.03). No patient with mutated IDH had chromosome 5 abnormalities, TP53 mutations or recurrent balanced translocations. 7/12 patients with mutated IDH1/2 had other gene mutations characteristic of AML (Table 1). The frequency of each of these other mutations were not different from patients with wildtype IDH1/2 (RUNX1, p=0.4; NPM1, p=0.2; FLT3, p=1.0; MLL, p=0.165; N-RAS, p=1.0). In conclusion, mutations of IDH1/2 were observed in 9% of patients with t-MDS/t-AML. They were not related to any specific type of therapy but perhaps associated with transformation from MDS to AML. IDH mutations clustered in the genetic pathway characterized by a normal karyotype and mutations of NPM1, and the pathway characterized by 7q−/−7 and RUNX1 point mutations. The significant association observed between IDH1/2 mutations and der(1;7)(q10;p10) may indicate that this cytogenetic aberration represents a specific entity, biologically distinct from other chromosome 7 abnormalities. This is also supported by the different clinical outcome between cases with der(1;7) and other cases with -7/7q- (Sanada et al, Leukemia 2007). Disclosures: No relevant conflicts of interest to declare.

Alternative genetic pathways for t-MDS and t-AML were previously suggested based on characteristic chromosome aberrations identical with those observed in de novo MDS and AML. The recurrent balanced translocations and inversions of these diseases in most cases result in chimeric rearrangement and inactivation of genes for hematopoietic transcription factors (class II mutations) which disturb cellular differen-tiation. Recently, activating point mutations or internal tandem duplications of genes for signal transduction in the receptor tyrosine kinase – RAS/BRAF pathway (class I mutations) have gained interest in de novo MDS and AML. A synergism between class I and class II mutations in the development of AML has been suggested. This hypothesis is now supported by our investigations of 140 unselected patients with t-MDS or t-AML for class I and class II mutations. A clustering of class I mutations in the different genetic pathways support the model for leukemic transformation.

The interval from diagnosis of chronic myelocytic leukaemia (CML) to onset of blastic transformation (BT) can vary from days to several years. This blastic phase of CML is indistinguishable from acute myelocytic leukaemia (AML), both clinically and morphologically. The Ph 1 chromosome has occasionally been demonstrated in acute leukaemia and it has been suggested that these cases may represent CML presenting in BT. 2 such patients are reported, in 1 of whom the characteristics after treatment further confirmed the diagnosis of CML. Differentiation between CML presenting in BT and AML has both prognostic and therapeutic value. For this reason it is recommended that cytogenetic screening for the Ph 1 chromosome should be included in the initial examination of patients with acute leukaemia.

Activating mutations of the PTPN11 gene encoding the SHP2 tyrosine phosphatase is the most common genetic abnormality in juvenile myelomonocytic leukemia and is sporadically observed in myelodysplasia (MDS) and acute myeloid leukemia (AML). An unselected series of 140 patients with therapy-related MDS or AML were investigated for mutations of PTPN11 in Exons 3, 4, 8, and 13. Four cases had mutations of the gene; three of these had deletions or loss of chromosome arm 7q. Two cases had rare balanced translocations to chromosome band 21q22 with rearrangement of the RUNX1 gene and the other two patients had rare balanced translocations to chromosome band 3q26 with rearrangement of the EVI1 gene. The findings support cooperation between so called Class I and Class II mutations in leukemogenesis.

Therapy-related acute myeloid leukemia (AML), often presenting as therapy-related myelodysplasia, is the most serious long-term complication of cancer chemotherapy. This disease offers a unique opportunity to study leukemogenesis by relating specific cytogenetic and genetic abnormalities to the biologic effects of cytostatic agents. Two types of drugs, alkylating agents and topoisomerase II inhibitors, have been shown to induce therapy-related leukemia.High risks of therapy-related myelodysplasia and AML were first reported in patients with multiple myeloma who had been treated with melphalan.1 Subsequently, almost all other alkylating agents in clinical use have been shown to be leukemogenic in patients treated for a . . .

A consecutive series of 21 previously untreated patients with low-grade non-Hodgkin lymphomas were treated with mitoxantrone 5 mg/m2 daily for 3 days every 3 weeks. The cumulative dose did not exceed 165 mg/m2 in any patient. In this group, 7 patients had small lymphocytic lymphomas, 10 patients had follicular small cleaved cell lymphomas, and 4 patients had follicular mixed small-and large-cell lymphomas. Of the 21 patients, 20 obtained remission (complete in 6, partial in 14), and 15 of these are still in remission. Relapse-free survival is 68% at 2 years. None of the patients has died. Nonhematologic toxicity was modest. No severe alopecia was seen, and only 6 patients had nausea and vomiting (WHO grade 1–3). No cardiac toxicity was seen. In conclusion, mitoxantrone is a highly active and well-tolerated drug in this subset of patients. Hematologic toxicity, especially leukopenia, was dose limiting, and a reduction of the dose was necessary in 15 out of the 21 patients.

A highly increased risk of myelodysplasia (MDS) and acute myeloid leukaemia (AML) is well established in patients previously treated for other malignancies with alkylating agents or topoisomerase II inhibitors. More recently, single cases of acute lymphoblastic leukaemia (ALL), often presenting balanced translocations involving chromosome band 11q23, have been observed. We present two such cases with t(4;11)(q21;q23), one of whom had previously received only single-agent chemotherapy with 4-epi-doxorubicin. A review of the literature since 1992 including these two patients reveals a total of 23 cases of ALL or lymphoblastic lymphoma after chemotherapy presenting balanced translocations to 11q23. All 23 patients had previously received at least one topoisomerase II inhibitor, and in two patients 4-epi-doxorubicin had been administered as single-agent chemotherapy for breast cancer. The latency period to development of t-ALL was 24 months or less in 20 out of 22 cases. The MLL gene was found to be rearranged in 14 out of 14 cases, and in three out of six cases the breakpoint was at the telomeric part of the gene, as observed in most cases of AT AML following therapy with topoisomerase II inhibitors. These results indicate that patients with ALL and balanced translocations to chromosome band 11q23 following chemotherapy with topoisomerase II inhibitors in the future should be included with cases of MDS or AML in calculations of risk of leukaemia.

Most cases of therapy-related acute nonlymphocytic leukemia or preleukemia show chromosome aberrations, primarily loss of whole chromosomes No. 5 and/or No. 7 or the long arms of these two chromosomes. Other abnormalities involve chromosome No. 21, often rearranged at band 21q22, and chromosome No. 17, in some cases rearranged at band 17p13. Important cellular genes have recently been localized to these regions, including the gene for one hematopoietic growth factor and the gene for the receptor for another hematopoietic growth factor. It is suggested that the total loss or change of structure or expression of some of these genes resulting from the various chromosome aberrations may be of pathogenetic significance in therapy-related acute nonlymphocytic leukemia.

In a multi‐centre study in which data from all Danish Hodgkin patients have been registered since 1971, all patients in supradiaphragmatic stages I or II, as confirmed by staging laparotomy, were randomized to either radiotherapy (RT) to supra‐ and infradiaphragmatic lymph node regions (total nodal irradiation, TNI), or RT to a mantle field followed by 6 cycles of MOPP combination chemotherapy (RT+ CT). Interim results up to July 1979, when 237 patients had entered the study, showed a treatment failure rate of 19/117 in the TNI group and 4/120 in the RT+CT group (P < 0.05). 19 of the 23 relapsing patients were under the age of 40, and 14 in the TNI group and 3 in the RT+CT group belonged to stage II. 13 patients had nodular sclerosis, 9 had mixed cellularity and 1 had lymphocytic predominance histology. 12 of the 19 relapsing patients in the TNI group had hilar or mediastinal involvement as against 51 of the 117 patients in the entire group. Most of the TNI failures could be retreated, and as yet there is no difference in the overall survival.