Can GSTM1 and GSTT1 polymorphisms predict clinical outcomes of chemotherapy in gastric and colorectal cancers? A result based on the previous reports.
Topic: Radiation/Chemotherapy

Gastric and colorectal cancers remain the major causes of cancer-related death. Although chemotherapy improves the prognosis of the patients with gastrointestinal cancers, some patients do not benefit from therapy and are exposed to the adverse effects. The polymorphisms in genes including GSTM1 and GSTT1 have been explored to predict therapeutic efficacy; however, the results were inconsistent and inconclusive.

PICO
Population: Patients with gastric and colorectal cancers undergoing chemotherapy
Intervention: Testing for GSTM1 and GSTT1 polymorphisms to predict therapeutic efficacy of chemotherapy
Comparison: Standard chemotherapy without genetic testing
Outcomes: Clinical outcomes of chemotherapy, including response to treatment and adverse effects

Included studies:
title: Comprehensive analysis of excision repair complementation group 1, glutathione S-transferase, thymidylate synthase and uridine diphosphate glucuronosyl transferase 1A1 polymorphisms predictive for treatment outcome in patients with advanced gastric cancer treated with FOLFOX or FOLFIRI.
abstract: Oxaliplatin and irinotecan have proven effective in the treatment of gastric cancer. We attempted to determine whether single nucleotide polymorphisms in ERCC1, GST, TS and UGT1A1 predicted overall survival in gastric cancer patients receiving FOLFOX and/or FOLFIRI chemotherapy. Total genomic DNA was extracted from the whole blood of patients. The PCR-restriction fragment length polymorphism technique was applied in order to detect the known variant sites of ERCC1, GST, TS and UGT1A1. The response rate of FOLFOX (N=75) was 24%. Grade 3-4 neutropenia and neurotoxicity were observed at frequencies of 34.7 and 16%, respectively. TTP and OS of first-line administration of FOLFOX (N=35) were 3.1 months (95% CI, 0.1-6.1 months) and 13.9 months (95% CI, 12.2-15.6 months), respectively. Only the GSTM1 positive genotype exhibited a significantly better time to progression (P=0.023). However, significant genotypic variation of TS, GST and ERCC1, which was assumed to affect the activity of oxaliplatin, was not observed to affect RR, toxicity and overall survival. The response rate of FOLFIRI (N=74) was 23%. Grade 3-4 neutropenia and diarrhea were observed in 55.4 and 9.5% of cases, respectively. TTP and OS of first-line administration of FOLFIRI (N=33) was 4.9 months (95% CI, 3.5-6.4 months) and 19.0 months (95% CI, 8.5-29.5 months). The low expression type (2R/2R, 2R/3C and 3C/3C) of TS was associated with a high incidence of grade >or=3 neutropenia. However, significant genotypic variation of UGT1A1, which was assumed to affect irinotecan toxicity, was not observed to affect RR, toxicity or survival. In this study, the GSTM1 positive genotype evidenced a significantly better time to progression in cases of advanced gastric cancer being treated with FOLFOX. The low expression type (2R/2R, 2R/3C and 3C/3C) of TS was associated with a high incidence of grade >or=3 neutropenia in cases of advanced gastric cancer treated with FOLFIRI.
title: A prospective validation pharmacogenomic study in the adjuvant setting of colorectal cancer patients treated with the 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX4) regimen.
abstract: The discovery of pharmacogenomic markers in colorectal cancer (CRC) could be setting-specific. FOLFOX4 is employed in the adjuvant and metastatic setting in CRC. This prospective study is aimed to validate in the adjuvant setting the pharmacogenomic markers of toxicity reported in the metastatic setting (that is, GSTP1-rs947894, and -rs1138272; GSTM1-null genotype; AGXT-rs4426527, -rs34116584 and del-74 bp), and to discover additional markers. CRC patients (n=144) treated with adjuvant FOLFOX4 were genotyped for 57 polymorphisms in 29 genes. Grade ≥ 2 neurotoxicity was associated (false discovery rate-adjusted q-value <0.1) with single-nucleotide polymorphisms in ABCC1 (rs2074087: odds ratio=0.43(0.22-0.86)), and ABCC2 (rs3740066: 2.99(1.16-7.70); rs1885301: 3.06(1.35-6.92); rs4148396: 4.69(1.60-13.74); rs717620: 14.39(1.63-127.02)). hMSH6-rs3136228 was associated with grade 3-4 neutropenia (3.23(1.38-7.57), q-value=0.0937). XRCC3-rs1799794 was associated with grade 3-4 non-hematological toxicity (8.90(2.48-31.97), q-value=0.0150). The markers previously identified in metastatic CRC were not validated. We have identified new markers of toxicity in genes of transport and DNA repair. If validated in other studies, they could help to identify patients at risk of toxicity.
title: Polymorphisms in p53, GSTP1 and XRCC1 predict relapse and survival of gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy.
abstract: The aim of this study was to assess whether genetic polymorphisms in p53, glutathione S-transferase P1 (GSTP1), GSTM1, excision repair cross complementing group 1 (ERCC1) and X-ray repair cross-complementing group 1 (XRCC1) genes are associated with clinical outcome of gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy.
title: Relationship between single nucleotide polymorphisms and haplotypes in DPYD and toxicity and efficacy of capecitabine in advanced colorectal cancer.
abstract: To explore the effect of dihydropyrimidine dehydrogenase (DPD) single nucleotide polymorphisms (SNP) and haplotypes on outcome of capecitabine.
title: Pharmacogenetic profiling in patients with advanced colorectal cancer treated with first-line FOLFOX-4 chemotherapy.
abstract: The objective is to investigate whether polymorphisms with putative influence on fluorouracil/oxaliplatin activity are associated with clinical outcomes of patients with advanced colorectal cancer treated with first-line oxaliplatin, folinic acid, and fluorouracil palliative chemotherapy.
title: Pharmacogenetic profiling and clinical outcome of patients with advanced gastric cancer treated with palliative chemotherapy.
abstract: To investigate whether polymorphisms with putative influence on fluorouracil/cisplatin activity are associated with clinical outcomes of patients with advanced gastric cancer (AGC).
title: Clinical importance of risk variants in the dihydropyrimidine dehydrogenase gene for the prediction of early-onset fluoropyrimidine toxicity.
abstract: We investigated the clinical relevance of dihydropyrimidine dehydrogenase gene (DPYD) variants to predict severe early-onset fluoropyrimidine (FP) toxicity, in particular of a recently discovered haplotype hapB3 and a linked deep intronic splice site mutation c.1129-5923C>G. Selected regions of DPYD were sequenced in prospectively collected germline DNA of 500 patients receiving FP-based chemotherapy. Associations of DPYD variants and haplotypes with hematologic, gastrointestinal, infectious, and dermatologic toxicity in therapy cycles 1-2 and resulting FP-dose interventions (dose reduction, therapy delay or cessation) were analyzed accounting for clinical and demographic covariates. Fifteen additional cases with toxicity-related therapy delay or cessation were retrospectively examined for risk variants. The association of c.1129-5923C>G/hapB3 (4.6% carrier frequency) with severe toxicity was replicated in an independent prospective cohort. Overall, c.1129-5923G/hapB3 carriers showed a relative risk of 3.74 (RR, 95% CI = 2.30-6.09, p = 2 × 10(-5)) for severe toxicity (grades 3-5). Of 31 risk variant carriers (c.1129-5923C>G/hapB3, c.1679T>G, c.1905+1G>A or c.2846A>T), 11 (all with c.1129-5923C>G/hapB3) experienced severe toxicity (15% of 72 cases, RR = 2.73, 95% CI = 1.61-4.63, p = 5 × 10(-6)), and 16 carriers (55%) required FP-dose interventions. Seven of the 15 (47%) retrospective cases carried a risk variant. The c.1129-5923C>G/hapB3 variant is a major contributor to severe early-onset FP toxicity in Caucasian patients. This variant may substantially improve the identification of patients at risk of FP toxicity compared to established DPYD risk variants (c.1905+1G>A, c.1679T>G and c.2846A>T). Pre-therapeutic DPYD testing may prevent 20-30% of life-threatening or lethal episodes of FP toxicity in Caucasian patients.