408P - Dpyd Genotyping As a Predictive Biomarker of Toxicity in Breast Cancer

Abstract

ABSTRACT Aim: Capecitabine is an orally bioavailable pro-drug of 5-fluorouracil (5FU) used for the treatment of metastatic breast cancer (m-BC). Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme in the catabolism of 5FU and eliminates more than 80% of the administered drug. DPD deficiency is an autosomal recessive disorder associated with significant morbidity and mortality in those with complete or relative deficiency (incidence 0.1% and 5% respectively). Our aim was to determine whether DPD testing could be used as a biomarker of toxicity. Methods: Consecutive patients with m-BC who received capecitabine in our institution from December 2012 to December 2013 were identified. Records were reviewed for 1) admission to hospital, 2) cost-efficiency analysis of DPD testing and 3) capecitabine-associated toxicities. For all our outcomes we used descriptive analysis. DPD testing was done according to our institution's guidelines with the genotyping of four DPYD sequence variants associated with reduced DPD activity. Patients were divided into two groups (A) those who had DPD deficiency and (B) those who did not or who were not tested. Results: Forty-eight patients received capecitabine, F:M (46:2), mean age 57 years (range, 35-83). Two patients in each group were admitted to hospital: Group A for 17 and 52 days, Group B for 2 and 5 days. Cost of hospitalization for patients in group A was 9 times that of group B. The cost of DPD testing is Conclusions: This analysis suggests that testing for DPD deficiency could be a potentially useful predictive biomarker of toxicity in patients with m-BC planned to receive capecitabine. Those with a genetic variant could either avoid capecitabine or start at a reduced dose. We plan to prospectively validate these results by implementing DPD testing for a period of one year in this patient group. Disclosure: All authors have declared no conflicts of interest.