The clinical relevance of multiple DPYD polymorphisms on patients candidate for fluoropyrimidine based-chemotherapy. An Italian case-control study

Background: Deleterious polymorphisms in the gene encoding DPD (DPYD) may result in severe reduction of DPD enzymatic activity that causes life-threatening toxicities when the standard dose of fluorouracil is used. The best panel of single-nucleotide polymorphism (SNPs) of DPYD is not well defined. Methods: In 2011, we began screening DPYD*2A in patients candidate for fluoropyrimidine-based chemotherapy. We planned a case-control study with all cases of DPYD*2A wild type who developed toxicity ≥G3 and with a cohort of patients who did not present severe toxicities. Then, we tested the additional SNPs: c.2846A>T, c.1679T>G, c.2194G>A. Results: From 2011 to 2016, we screened 1827 patients for DPD deficiency; of those, 31 subjects (1.7%) showed DPYD*2A SNP. We selected 146 subjects who developed severe toxicities (Cases) and 220 patients who experienced no or mild toxicities (Controls); 53 patients carried one of the additional SNPs: 35 subjects (66%) fell into the Cases and 18 (34%) into the Controls (p < 0.0001). c.2194G>A was the most frequent SNP (12.5%) and showed a correlation with neutropenia. We confirmed that c.2846A>T and c.1679T>G were related to various toxicities. Conclusions: The additional DPYD polymorphisms could enhance the prevention of fluoropyrimidine toxicity. c.2194G>A is the most frequent polymorphism and it was found to be associated with neutropenia.