ABCB1(MDR 1) Polymorphisms and Progression-Free Survival among Women with Ovarian Cancer following Paclitaxel/Carboplatin Chemotherapy

Abstract

AbstractPurpose: The human ABCB1 gene encodes P-glycoprotein, which transports a broad range of anticancer drugs, including paclitaxel. Although the functional consequences of ABCB1 polymorphisms have been the subject of numerous studies, few have assessed the association with clinical outcome.Experimental Design: We assessed the association between the 2677G>T/A, 3435C>T, and 1236C>T ABCB1 polymorphisms and progression-free and overall survival in 309 patients from the Australian Ovarian Cancer Study treated with paclitaxel/carboplatin and subsequently tested significant observations in an independent validation set.Results: Women who carried the minor T/A alleles at the 2677G>T/A polymorphism were significantly less likely to relapse following treatment compared with homozygote GG carriers (PLog-rank = 0.001) in the Australian Ovarian Cancer Study cohort. Subgroup analyses showed that this effect was limited to cases with residual disease ≤1 cm (PLog-rank = 0.0004), not for those with residual disease >1 cm (PLog-rank = 0.3). This effect was not confirmed in an independent validation set of carboplatin/paclitaxel-treated patients (n = 278) using a higher residual disease cut point (≤2 cm). However, analysis of the unrestricted data set expanded to include docetaxel-treated patients (n = 914) did support an effect of the 2677T/A allele in patients with no macroscopic residual disease (hazard ratio, 0.70; 95% confidence interval, 0.46-1.04; Pone-sided = 0.039).Conclusion: Our findings indicate that there is an effect of the 2677G>T/A polymorphism on progression-free survival in ovarian cancer patients who are treated with a taxane/carboplatin, which is dependent on the extent of residual disease, with a better prognosis for patients with the 2677T/A allele and minimal residual disease.