Genetic polymorphisms and ethnic difference in outcome of adjuvant FOLFOX chemotherapy in Korean patients with colon cancer.

Abstract

623 Background: Ethnic diversity of genetic polymorphism can result in individual differences in the efficacy and toxicity of cancer chemotherapy. Methods: A total of 292 Korean patients (183 men and 109 women) from six hospitals in Korea were prospectively enrolled. Patients had resected stage III or high-risk stage II colon cancer and were treated with 12 cycles of adjuvant oxaliplatin plus leucovorin plus 5-fluorouracil (FOLFOX) chemotherapy. 20 germline polymorphisms in 10 genes (TS, MTHFR, ERCC1, XPD, XRCC1, ABCC2, AGXT, GSTP1, GSTT1 and GSTM1) were analyzed from peripheral blood. TS genotype in 5’UTR was classified as ‘high’ (2R/3G, 3C/3G, and 3G/3G) or ‘low’ (2R/2R, 2R/3C, and 3C/3C). Results: Most patients (86.3%) received 12 complete cycles of FOLFOX chemotherapy. In contrast to previous studies in Caucasians, neutropenia (grade 3–4, 60.5%) was frequently observed in our Korean patients, whereas only 16.4% experienced grade 2 or more sensory neuropathy. Neutropenia was more frequent in MTHFR 677TT [adjusted odds ratio (OR) 2.32, 95% confidence interval (CI) 1.19–4.55] and ERCC1 19007TT (adjusted OR 4.58, 95% CI 1.20–17.40) genotypes. Patients harboring XRCC1 23885GG had lower risk of neuropathy (adjusted hazard ratio 0.56, 95% CI 0.32-0.99) and longer time to the onset of grade 2-4 neuropathy. MTHFR 677TT and XRCC1 23885GG genotype was also more prevalent in Koreans compared to Caucasians, and the difference of genotypic frequency could partly explain the ethnically different toxicity profile. After median 49.4 months of follow-up, there were 58 (19.9%) relapses and 19 (6.5%) deaths. TS ‘low’ genotype [adjusted hazard ratio (OR) 1.83, 95% CI 1.003–3.34] was significantly related to shorter disease-free survival. Overall survival was not significantly different according to the polymorphisms. Conclusions: Polymorphisms in MTHFR, XRCC1 and TS are related to toxicities and disease-free survival in patients with colon cancer. These polymorphisms may explain the ethnic difference in toxicity profile following adjuvant FOLFOX chemotherapy.