Purpose: The primary aim of this study was to characterize the 6-month overall survival and toxicity associated with second-line capecitabine treatment of advanced pancreatic cancer patients harboring the TYMS *2/*2 allele. The secondary aim was to analyze the response rate and pharmacokinetics of capecitabine-based therapy in this patient population. Lastly, TYMS, ATM and RecQ1 single nucleotide polymorphism were analyzed relative to overall survival in patients screened for study participation.
Methods: Eighty patients with stage IV pancreatic cancer were screened for the *2/*2 TYMS allele. Patients with the *2/*2 TYMS polymorphism were treated with capecitabine, 1,000 mg/m2 twice daily for 14 consecutive days of a 21 day cycle. Screened patients not possessing TYMS *2/*2 were monitored for survival. Pharmacokinetic analysis was done during Cycle 1 of the therapy.
Results: Sixteen of the 80 screened patients tested positive for *2/*2 TYMS variant. Four out of the 16 eligible patients were treated on study. The study was terminated early due to poor accrual and increased toxicity. Three patients experienced grade 3 non-hematologic toxicities of palmer-plantar erythrodysesthesia, diarrhea, nausea and vomiting. Grade 2 toxicities were similar and occurred in all patients. Only one patient was evaluable for response after completion of three cycles of therapy. The presence of the *2/*2 TYMS genotype in all of the screened patients trended toward a decreased overall survival.
Conclusion: To our knowledge, this study represents the first genotype-directed clinical trial for patients with pancreatic adenocarcinoma. Although the study was closed early, it appears capecitabine therapy in pancreatic cancer patients harboring the TYMS *2/*2 variant may be associated with increased non-hematologic toxicity. This study also demonstrates the challenges performing a genotype-directed study in the second-line setting for patients with advanced pancreatic cancer.