Implementing Dpyd*2a Genotyping In Clinical Practice: The Quebec, Canada, Experience

Background Fluoropyrimidines are used in chemotherapy combinations for multiple cancers. Deficient dihydropyrimidine dehydrogenase activity can lead to severe life-threatening toxicities. DPYD*2A polymorphism is one of the most studied variants. The study objective was to document the impact of implementing this test in routine clinical practice.Methods We retrospectively performed chart reviews of all patients who tested positive for a heterozygous or homozygous DPYD*2A mutation in samples obtained from patients throughout the province of Quebec, Canada.Results During a period of 17 months, 2,617 patients were tested: 25 patients tested positive. All were White. Twenty-four of the 25 patients were heterozygous (0.92%), and one was homozygous (0.038%). Data were available for 20 patients: 15 were tested upfront, whereas five were identified after severe toxicities. Of the five patients confirmed after toxicities, all had grade 4 cytopenias, 80% grade >= 3 mucositis, 20% grade 3 rash, and 20% grade 3 diarrhea. Eight patients identified with DPYD*2A mutation prior to treatment received fluoropyrimidine-based chemotherapy at reduced initial doses. The average fluoropyrimidine dose intensity during chemotherapy was 50%. No grade >= 3 toxicities were observed. DPYD*2A test results were available in an average of 6 days, causing no significant delays in treatment initiation.Conclusion Upfront genotyping before fluoropyrimidine-based treatment is feasible in clinical practice and can prevent severe toxicities and hospitalizations without delaying treatment initiation. The administration of chemotherapy at reduced doses appears to be safe in patients heterozygous for DPYD*2A.Implications for Practice Fluoropyrimidines are part of chemotherapy combinations for multiple cancers. Deficient dihydropyrimidine dehydrogenase activity can lead to severe life-threatening toxicities. This retrospective analysis demonstrates that upfront genotyping of DPYD before fluoropyrimidine-based treatment is feasible in clinical practice and can prevent severe toxicities and hospitalizations without delaying treatment initiation. This approach was reported previously, but insufficient data concerning its application in real practice are available. This is likely the first reported experience of systematic DPYD genotyping all over Canada and North America as well.