ASCO University 2016

Background: DPD deficiency is a pharmacogenetic syndrome associated with dose-limiting toxicity to fluoropyrimidines. Oncologists are expected to recognize and diagnose this syndrome, as toxicities could be fatal. Over 40 single nucleotide polymorphisms (SNPs) and deletions have been identified within the DPYD gene. IVS14+1G>A (DPYD*2A) is the most common (40-50%) and best studied of these SNPs. Yet, it showed a median sensitivity of 30% and is absent in Japanese, Korean and African Americans. Overall, the data on DPYD testing is insufficient to provide enough guidance to diagnose DPD deficiency. Herein we describe our experience with germline pharmacogenomics in patients with DPD deficiency.

Methods: Between 2011 and 2015, 35 patients with gastrointestinal malignancies were tested for DPYD mutations; 17 were tested after developing toxicities to treatment and 18 were tested prior to treatment. IVS14+1G>A (DPYD*2A) was tested in all patients. DPYD c.85T>C (DPYD*9A), DPYD c.1679T>G (DPYD*13A), DPYD c.-1590T>C, and DPYD c.2846A>T were tested in 24 patients (69%) only. We explored the association between DPYD mutations and fluoropyrimidine-related toxicity using Fisher’s exact test.