Survival analysis in association with GST gene polymorphism and Treatment outcomes of Gemcitabine and Cisplatin/Carboplatin-based chemotherapy among patients with Gallbladder Carcinoma.

ABSTRACT

PURPOSE: Majority of the gallbladder cancer (GBC) cases are diagnosed at an advanced stage where chemotherapy alone (or in combination with other treatment methods) is mainly opted as therapeutic approach. However, success or failure of this approach largely depends on the interindividual genetic differences. Careful consideration on the genetic association could assist in the evaluation of patient's treatment response and survival rate. Hence, the present study aims to investigate the survival of patients with GBC and their treatment response to gemcitabine and cisplatin/carboplatin-based chemotherapy in association with Glutathione S-transferase (GSTs) gene polymorphism. MATERIAL AND METHODS: A total of 216 histologically confirmed cases of gallbladder cancer were recruited. A total of 180 patients were treated with gemcitabine and cisplatin/carboplatin-based chemotherapy. GSTM1, GSTT1, and GSTP1 genotypes were determined by multiplex PCR and by PCR restriction fragment length polymorphism (PCR-RFLP), respectively. The influence of genetic polymorphism on overall survival was analyzed by Kaplan-Meier method, survival rate difference was analyzed by log-rank test, and hazard ratio for mortality outcomes was estimated using Cox regression method. RESULTS: GBC patients having genotype GSTP1 (AG + GG) showed poor 3-year survival rate of 0.8% compared to 10.9% of GSTP1 (AA) genotype (χ2 = 6.456, P = 0.011). The multivariate Cox regression results showed that the death risk was significantly higher in GSTP1 (AG + GG) genotype (HR = 3.858, P = 0.050). We found no association of GSTM1 and GSTT1 gene polymorphism with the survival; however, the combined genotypes of GSM1/GSTP1, GSTT1/GSTP1, and GSTM1/GSTT1/GSTP1 were associated with survival (P = 0.053, 0.006, and 0.058, respectively). Increased death hazard was noted by the genotype combinations of GSTM1+/GSTP1AG + GG (HR = 3.484, P = 0.024), GSTM1-/GSTP1AG + GG (HR = 2.721, P = 0.014), GSTT1+/GSTP1AG + GG (HR = 20.690, P = 0.001), and GSTT1-/GSTP1AA (HR = 26.111, P < 0.0001). Our findings indicate that chemotherapy treatment response of GSTP1 (AG + GG) has 1.62-fold increased risk for progression compared to GSTP1 (AA) genotype (p = 0.018); however, none of the genotypes showed association with overall survival and death risk after chemotherapeutic treatment. CONCLUSION: We found that the presence of GSTP1 (AG + GG) genotype showed survival disadvantage and poor treatment outcomes in response to gemcitabine and cisplatin/carboplatin-based chemotherapy. This could serve as biomarker, and future research in pharmacogenomics will definitely pave the way for the development of better treatment approach for GBC.