INTRODUCTION:Although fluoropyrimidines are widely prescribed to older patients, studies investigating predictors for chemotherapy intolerance in this patient population are scarce. Therefore, we aimed to identify predictors of poor treatment tolerability in older patients receiving fluoropyrimidine-based chemotherapy. MATERIALS AND METHODS:Patients aged ≥70 years who received fluoropyrimidine-based chemotherapy were selected from the prospective, multicentre, non-randomized Alpe2U study. Before treatment initiation, participants underwent a geriatric assessment investigating the somatic, nutritional, functional, and mental domains. Predictors of the composite endpoint "poor treatment tolerability," defined as either Common Toxicity Criteria Adverse Events (CTCAE) grade 3-5 chemotherapy-related toxicity, dose reduction, or treatment discontinuation within the first two cycles, were analysed using uni- and multivariable logistic regression models. RESULTS:Of the 194 included patients, median age was 75 (interquartile range 73-79) years and the most common tumour types were colorectal (60%) and esophagogastric (19%) cancer. Most patients (89%) received capecitabine-based chemotherapy. Poor treatment tolerability within the first two cycles was seen in 31% of patients. In multivariable analyses, associations with poor treatment tolerability were found for deficits in 3-4 geriatric domains compared with 0 deficits (odds ratio [OR] 4.03, 95% confidence interval [CI] 1.09-14.97, p = 0.04) and for combination chemotherapy (OR 2.83, 95% CI 1.31-6.09, p = 0.008). DISCUSSION:Having deficits in multiple geriatric domains and combination chemotherapy were predictors of poor treatment tolerability within the first two cycles in older patients treated with fluoropyrimidine-based chemotherapy. These findings highlight the importance of a geriatric assessment before fluoropyrimidine administration to estimate risk of treatment intolerance.

PURPOSE DPYD -guided fluoropyrimidine dosing effectively limits the risk of severe toxicity while maintaining clinical efficacy. However, recent data suggest that c.1236G>A variant carriers, starting with a 25% reduced dose, have shorter progression-free survival than wild-type patients receiving a full dose. Although overall survival was unaffected, further investigation is warranted. To address this, we retrospectively compared 5-fluorouracil (5-FU) exposure between c.1236G>A variant carriers and DPYD wild-type patients. MATERIALS AND METHODS Pharmacokinetic data from nine clinical trials involving capecitabine-treated patients were pooled. Blood samples were collected before and after administration of capecitabine to assess systemic levels of its metabolites, including 5-FU. Capecitabine dosages were reduced for c.1236G>A variant carriers in accordance with the clinical guidelines at the time of study execution and varied from no reduction (n = 11) to a 25% (n = 16) or 50% (n = 8) reduction. Pharmacokinetic exposure, expressed as area under the plasma concentration-time curve (AUC 0-∞ ), was determined using noncompartmental analysis and dose-normalized to 850 mg/m 2 . RESULTS In total, 35 heterozygous c.1236G>A patients and 66 DPYD wild-type patients were evaluable. Patients carrying c.1236G>A who received a 50% dose reduction had a lower dose-normalized geometric mean 5-FU exposure (234 ng·h/mL coefficient of variation [CV = 43%]) compared with fully dosed c.1236G>A carriers (553 ng·h/mL [CV = 51%]) and fully dosed DPYD wild-type patients (582 ng·h/mL [CV = 48%]; P < .001). All c.1236G>A carriers who received a 50% dose reduction had AUC 0-∞ values below the AUC 0-∞ range observed in the wild-type group. CONCLUSION Our findings indicate that an upfront 25% dose reduction for capecitabine in c.1236G>A carriers is likely more appropriate than the currently recommended 50% dose reduction. We stress the importance of individual dose titration in c.1236G>A carriers to avoid both over- and undertreatment.

BACKGROUND:DPYD-guided dosing enhances safety of fluoropyrimidine-based chemotherapy. However, approximately 23 % of patients still experience severe toxicity unexplained by the four commonly tested DPYD-variant alleles. Elevated pre-treatment uracil levels have been proposed as a surrogate marker for reduced DPD activity and an independent predictor of toxicity. This prospective study evaluated whether uracil-guided dose individualisation can reduce severe fluoropyrimidine-induced toxicity in DPYD wild-type patients. METHODS:Pre-treatment plasma uracil levels were quantified in patients scheduled to receive fluoropyrimidine-based therapy. DPYD wild-type individuals with uracil concentrations > 16 ng/mL (DPYDwt/Uhigh) received a 50 % dose reduction, in accordance with French RNPGx guidelines. The incidence of grade ≥ 3 fluoropyrimidine-related toxicity was compared between dose-reduced DPYDwt/Uhigh patients, DPYDwt patients with uracil ≤ 16 ng/mL (DPYDwt/Unormal), and a historical cohort of DPYDwt/Uhigh patients treated at full dose. Pharmacokinetic data were compared to a second historical cohort. RESULTS:Among 612 evaluable patients, 22 were DPYDwt/Uhigh. The incidence of severe toxicity in the dose-reduced group was significantly lower than in historical full-dose DPYDwt/Uhigh patients (20 % vs 43 %, P = 0.03) and comparable during the first 2 treatment cycles to DPYDwt/Unormal patients (10 % vs 11 %). However, 5-fluorouracil exposure was markedly reduced in nineteen dose-reduced DPYDwt/Uhigh patients (177 vs 381 ng*h/mL), while five subsequently treated fully dosed DPYDwt/Uhigh patients exhibited comparable exposure to historical wild-type controls (456 vs 381 ng*h/mL). No correlation was found between uracil levels and DPD enzyme activity (R=-0.006, P = 0.98). CONCLUSION:Uracil-guided dosing of fluoropyrimidines may reduce toxicity risk but leads to subtherapeutic 5-fluorouracil exposure in DPYD wild-type patients. This indicates that these patients are treated sub-optimally and that uracil is not a reliable predictor of DPD deficiency in DPYD wild-type patients.

BACKGROUND/AIM:More than 90% of colorectal cancers (CRC) have alterations in WNT signaling. Eight to ten percent of patients with metastatic Kirsten rat sarcoma virus - wild type (KRAS-WT) CRC have B-Raf Proto-Oncogene, Serine/Threonine Kinase (BRAF) mutations and do not benefit from epidermal growth factor receptor (EGFR) antibodies. The addition of a porcupine inhibitor could increase the response rate in patients with BRAFV600E-mutated KRAS-WT metastatic CRC (mCRC) with WNT pathway alterations. PATIENTS AND METHODS:We report two cases of severe bone toxicities during treatment with the BRAF inhibitor encorafenib, the EGFR-targeting monoclonal antibody cetuximab, and the porcupine inhibitor WNT974 in the phase 1B study NCT02278133. RESULTS:Patient 1, a 66-year-old man with BRAFV600E-mutated KRAS-WT mCRC and an RNF43 mutation, developed multiple rib fractures and collapse of thoracic vertebrae 10 and 11. Autopsy revealed no metastases at fracture sites; histology demonstrated a thin, porous cortex and poor trabecular bone structure. Immunohistochemistry assessed key WNT pathway components. Patient 2, a 70-year-old man with similar mutations, experienced a toe fracture, multiple rib fractures, osteopenia, and altered bone biomarkers indicative of disrupted bone turnover. CONCLUSION:The two patients described developed severe bone toxicities including rib fractures, a toe fracture, osteoporotic thoracic collapses, hypercalcemia, and alternated bone biomarkers. These cases highlight the potential skeletal risks associated with dual MAPK and WNT pathway inhibition.

Supplementary Fig. S5. The set of eight genes from the MPAS signature was highly enriched in a GSEA analysis using as input the list of genes sorted on the results from the differential analysis “on treatment” vs. “baseline.”

Supplementary Fig. S2. Vorinostat plasma concentrations over time on days 1 and 14 of the first treatment cycle.

Supplementary Table S3. Results of RNA sequencing.

Supplementary Table S2. Tissue and ctDNA results.

Supplementary Table S1. Representativeness of study participants.

Supplementary Fig. S1. Spider plot showing the best response and change in size of progressive target lesions per patient during treatment.

PURPOSE:The development of resistance limits the clinical benefit of BRAF and MEK inhibitors (BRAFi/MEKi) in BRAFV600-mutated melanoma. It has been shown that short-term treatment (14 days) with vorinostat was able to initiate apoptosis of resistant tumor cells. We aimed to assess the antitumor activity of sequential treatment with vorinostat following BRAFi/MEKi in patients with BRAFV600-mutated melanoma who progressed after initial response to BRAFi/MEKi. PATIENTS AND METHODS:Patients with BRAFi/MEKi-resistant BRAFV600-mutated melanoma were treated with vorinostat 360 mg once daily for 14 days followed by BRAFi/MEKi. The primary endpoint was an objective response rate of progressive lesions of at least 30% according to Response Evaluation Criteria in Solid Tumors 1.1. Secondary endpoints included progression-free survival, overall survival, safety, pharmacokinetics of vorinostat, and translational molecular analyses using ctDNA and tumor biopsies. RESULTS:Of the 26 patients with progressive BRAFi/MEKi-resistant BRAFV600-mutated melanoma receiving treatment with vorinostat, 22 patients were evaluable for response. The objective response rate was 9%, with one complete response for 31.2 months and one partial response for 14.9 months. Median progression-free survival and overall survival were 1.4 and 5.4 months, respectively. Common adverse events were fatigue (23%) and nausea (19%). ctDNA analysis showed emerging secondary mutations in NRAS and MEK in eight patients at the time of BRAFi/MEKi resistance. Elimination of these mutations by vorinostat treatment was observed in three patients. CONCLUSIONS:Intermittent treatment with vorinostat in patients with BRAFi/MEKi-resistant BRAFV600-mutated melanoma is well tolerated. Although the primary endpoint of this study was not met, durable antitumor responses were observed in a minority of patients (9%).

Background Dihydropyrimidine dehydrogenase (DPD) deficiency is the main known cause of life-threatening fluoropyrimidine (FP)-induced toxicities. We conducted a meta-analysis on individual patient data to assess the contribution of deleterious DPYD variants *2A/D949V/*13/HapB3 (recommended by EMA) and clinical factors, for predicting G4-5 toxicity. Methods Study eligibility criteria included recruitment of Caucasian patients without DPD-based FP-dose adjustment. Main endpoint was 12-week haematological or digestive G4-5 toxicity. The value of DPYD variants *2A/p.D949V/*13 merged, HapB3, and MIR27A rs895819 was evaluated using multivariable logistic models (AUC). Results Among 25 eligible studies, complete clinical variables and primary endpoint were available in 15 studies (8733 patients). Twelve-week G4-5 toxicity prevalence was 7.3% (641 events). The clinical model included age, sex, body mass index, schedule of FP-administration, concomitant anticancer drugs. Adding *2A/p.D949V/*13 variants (at least one allele, prevalence 2.2%, OR 9.5 [95%CI 6.7–13.5]) significantly improved the model ( p < 0.0001). The addition of HapB3 (prevalence 4.0%, 98.6% heterozygous), in spite of significant association with toxicity (OR 1.8 [95%CI 1.2–2.7]), did not improve the model. MIR27A rs895819 was not associated with toxicity, irrespective of DPYD variants. Conclusions FUSAFE meta-analysis highlights the major relevance of DPYD *2A/p.D949V/*13 combined with clinical variables to identify patients at risk of very severe FP-related toxicity.

Supplementary Figure S7. Secondary mutations detected in ctDNA.

Supplementary Fig. S4. Vorinostat O-glucuronide plasma concentrations over time on days 1 and 14 of the first treatment cycle.

Supplementary Fig. S6. MAPK pathway activity before and after vorinostat (day 14), sorted on the DESeq2 statistic from high to low.

Abstract Background The Alpe-DPD study (NCT02324452) demonstrated that prospective genotyping and dose-individualization using four alleles in DPYD (DPYD*2A/rs3918290, c.1236G > A/rs75017182, c.2846A > T/rs67376798 and c.1679 T > G/rs56038477) can mitigate the risk of severe fluoropyrimidine toxicity. However, this could not prevent all toxicities. The goal of this study was to identify additional genetic variants, both inside and outside DPYD, that may contribute to fluoropyrimidine toxicity. Methods Biospecimens and data from the Alpe-DPD study were used. Exon sequencing was performed to identify risk variants inside DPYD. In silico and in vitro analyses were used to classify DPYD variants. A genome-wide association study (GWAS) with severe fluoropyrimidine-related toxicity was performed to identify variants outside DPYD. Association with severe toxicity was assessed using matched-pair analyses for the exon sequencing and logistic, Cox, and ordinal regression analyses for GWAS. Results Twenty-four non-synonymous, frameshift, and splice site DPYD variants were detected in ten of 986 patients. Seven of these variants (c.1670C > T, c.1913 T > C, c.1925 T > C, c.506delC, c.731A > C, c.1740 + 1G > T, c.763 − 2A > G) were predicted to be deleterious. The carriers of either of these variants showed a trend towards a 2.14-fold (95% CI, 0.41–11.3, P = 0.388) increased risk of severe toxicity compared to matched controls (N = 30). After GWAS of 942 patients, no individual single nucleotide polymorphisms achieved genome-wide significance (P ≤ 5 × 10−8), however, five variants were suggestive of association (P < 5 × 10−6) with severe toxicity. Conclusions Results from DPYD exon sequencing and GWAS analysis did not identify additional genetic variants associated with severe toxicity, which suggests that testing for single markers at a population level currently has limited clinical value. Identifying additional variants on an individual level is still promising to explain fluoropyrimidine-related severe toxicity. In addition, studies with larger samples sizes, in more diverse cohorts are needed to identify potential clinically relevant genetic variants related to severe fluoropyrimidine toxicity.

Supplementary Fig. S3. 4-AOA plasma concentrations over time on days 1 and 14 of the first treatment cycle.

Beyond melanoma, BRAFV600E alterations are prevalent across multiple tumors. We conducted a basket trial (NCT02034110) to assess efficacy and safety of oral BRAF inhibitor dabrafenib (150 mg BD) plus MEK inhibitor trametinib (2 mg OD) in 206 patients (eight cohorts) with BRAFV600E-mutated advanced rare cancers. Patients with anaplastic carcinoma thyroid, biliary tract cancer, gastrointestinal stromal tumor, adenocarcinoma of small intestine, low-grade (eight histologies)/high-grade (seven histologies) glioma, hairy cell leukemia, and multiple myeloma were treated until unacceptable toxicity, disease progression, or death. Overall, median duration of exposure to dabrafenib and trametinib was 12.5 (1–82) and 12.0 (1–84) months, respectively. Primary endpoint was tumor response; secondary endpoints were duration of response, progression free and overall survival, and safety (investigator-assessed). Overall response rate was 56% (38.1%, 72.1%), 53% (37.7%, 68.8%), 0%, 67% (9.4%, 99.2%), 54% (25.1%, 80.8%), 33% (20.0%, 49.0%), 89% (77.8%, 95.9%), and 50% (18.7%, 81.3%), respectively. Median (95% confidence interval) duration of response was 14.4 (7.4, not reached), 8.9 (5.6, 13.7), not reached, 7.7 (not reached, not reached), not reached (5.5, not reached), 31.2 (7.4, 44.2), not reached, and 11.1 (5.6, not reached) months, respectively. Durable and clinically meaningful responses were observed in solid and hematological malignancies (21 histologies). Safety profile was acceptable; most frequent (≥20% patients) treatment-related adverse events were pyrexia (40.8%), fatigue (25.7%), chills (25.7%), nausea (23.8%), and rash (20.4%). The encouraging tumor-agnostic activity of dabrafenib plus trametinib is a promising approach in patients with BRAFV600E-mutated advanced rare cancers. These results supported the accelerated FDA approval for a tumor-agnostic BRAF+MEK inhibitor combination representing a precision medicine milestone. Median progression free and overall survival in BRAFV600E-mutated advanced rare cancer patients ATC(N=36) BTC(N=43) LGG(N=13) HGG(N=45) ASI (N=3) HCL(N=55) MM(N=10) PFS 6.7 (4.7, 13.8) 9.0 (5.5, 9.4) NE 5.5 (1.8, 13.7) 9.5 NE 6.3 (2.3, 12.9) OS 14.5 (6.8, 23.2) 13.5 (10.4, 17.6) 17.6 (9.5, 32.2) NE 21.8 (3.4, NR) NE 33.9 (2.9, 44.6) Patient in the GIST cohort (n=1) did not attain a complete or partial response. ASI, adenocarcinoma of small intestine; ATC, anaplastic thyroid cancer; BTC, biliary tract cancer; GIST, gastrointestinal stromal tumor; HCL, hairy cell leukemia; HGG, high grade (WHO G3/G4) glioma; LGG, low (WHO G1/G2) grade glioma; MM, multiple myeloma; NE, not evaluable; NR, not reached; OS, overall survival; PFS, progression free survival; WHO, World Health Organization. Citation Format: Vivek Subbiah, Robert J. Kreitman, Zev A. Wainberg, Anas Gazzah, Ulrik Lassen, Alexander Stein, Patrick Y. Wen, Sascha Dietrich, Maja JA Jonge, Jean-Yves Blay, Antoine Italiano, Kan Yonemori, Daniel C. Cho, Filip YFL de Vos, Philippe Moreau, Elena Elez Fernandez, Jan H. Schellens, Christoph C. Zielinski, Suman Redhu, Vanessa Q. Passos, Palanichamy Ilankumaran, Yung-Jue Bang. Tumor-agnostic efficacy and safety of dabrafenib plus trametinib in BRAFV600E-mutated rare cancers: ROAR basket study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT083.

Supplementary Figure 1. Mutation panel (OncoCarta panel v.1.0) tested in phase 1 expansion study (19 oncogenes and 225 mutations)