Frequency and clinical relevance of DPYD genetic variants in gastrointestinal cancer patients.

OBJECTIVE

To determine the prevalence of loss-of-function variants in the dihydropyrimidine dehydrogenase gene in patients with gastrointestinal neoplasms, assess their clinical relevance, and evaluate the  implementation of a multidisciplinary circuit at three months from its  implementation.

METHOD

This is a descriptive, observational and retrospective study, which  included adult patients with gastrointestinal cancer treated at a tertiary  university hospital who underwent dihydropyrimidine dehydrogenase genotyping between September 2019 and December 2020. The  variables collected were sex, age, type of cancer, location, stage, treatment received, indication of treatment and degree of toxicity  developed during the first three cycles. The genotyped variants were  rs3918290 (c.1905+1G>A), rs55886062 (c.1679T>G), rs67376798  (c.2846A>T) and rs75017182 (c.1129-5923C>G).

RESULTS

A total of 115 patients were included. The frequency of heterozygous dihydropyrimidine dehydrogenase variant carriers was 9.6% (11  patients). The most frequently identified variant was rs75017182 (6 patients). The second most common variant was rs67376798 (3 patients),  followed by rs3918290 (2 patients). No patients presented with the  rs55886062 variant. Two of the dihydropyrimidine dehydrogenase carriers  developed  grade 3-5 toxicity after the first cycle of a regimen that included  fluoropyrimidines. Both received full doses of fluoropyrimidine, since their  dihydropyrimidine dehydrogenase genotype was unknown before treatment  initiation. None of the dihydropyrimidine dehydrogenase carriers who began treatment with a reduced dose of fluoropyrimidine experienced grade 3-5  toxicity. Since the creation in October 2020 of a multidisciplinary team, with  the active participation of hospital pharmacists, the monthly average of dihydropyrimidine dehydrogenase genotyping studies has increased from 6.4  (January-October) to 17.5 (November-December).

CONCLUSIONS

The present study shows a relatively high prevalence of loss-of- function variants in the dihydropyrimidine dehydrogenase gene as well as the  importance of genotyping such variants before starting a treatment with  fluoropyrimidines. Hospital pharmacists can contribute to the implementation  of pharmacogenetics in daily clinical practice in a tertiary hospital.