Background: On account of the lack of predictive biomarkers of toxicity, we investigated whether polymorphisms of genes involved in fluoropyrimidine metabolism and 5-fluorouracil (5-FU) degradation rate were associated with outcomes of adjuvant capecitabine in patients with early stage gastrointestinal cancers.
Methods: Genotyping of DPYD GIVS14A, MTHFR C677T and A1298C SNPs were performed by pyro-sequencing technology. PCR analysis was used for genotyping TYMS-TSER. We also evaluated the 5-FU degradation rate, which determines the amount of drug consumed by PBMC in a time unit. Association of these variables with clinical outcome was evaluated using multivariate logistic regression analysis.
Results: One hundred forty-two patients with early stage colon (39%), rectal (28%), stomach (20%) and pancreatic (13%) cancer, treated with adjuvant capecitabine, were included in this retrospective analysis. Seventy and 20% of the patients suffered from at least one G1-4 and G3-4 adverse events, respectively. According to the 5-FU degradation rate, three and 13 patients were assigned as poor (<0.86 ng/mL/106 cells/min) and ultra-rapid (>2.1 ng/mL/106 cells/min) metabolizers, respectively. At a multivariate logistic regression analysis, an altered 5-FU degradation rate (values <0.86 or >2.10 ng/mL/106 cells/min) was associated with grade 3-4 adverse events (OR = 2.09, 95% CI: 1.14-3.82, P = 0.01). No correlation was reported between toxicity and gene polymorphisms except for hand-foot syndrome that was more frequent in the MTHFR 1298CC homozygous variant genotype (OR = 2.03, 95% CI 1.04-3.96, P = 0.03).
Conclusions: 5-FU degradation rate may be regarded as possible predictive biomarker of capecitabine toxicity in early stage gastrointestinal cancer.
Keywords: Adjuvant capecitabine; Gene polymorphisms; Oral fluoropyrimidines; Personalized medicine; Predictive biomarkers; Toxicity.