Overexpression of RRM1 and RRM2 has been associated with gemcitabine resistance. BRCA1 overexpression increases sensitivity to paclitaxel and docetaxel. We have retrospectively examined the effect of RRM1, RRM2 and BRCA1 expression on outcome to gemcitabine plus docetaxel in advanced non-small-cell lung cancer (NSCLC) patients.
Tumor samples were collected from 102 chemotherapy-naïve advanced NSCLC patients treated with gemcitabine plus docetaxel as part of a randomized trial. RRM1, RRM2 and BRCA1 mRNA levels were assessed by quantitative PCR and correlated with response, time to progression and survival. As BRCA1 levels increased, the probability of response increased (Odds Ratio [OR], 1.09: p = 0.01) and the risk of progression decreased (hazard ratio [HR], 0.99; p = 0.36). As RRM1 and RRM2 levels increased, the probability of response decreased (RRM1: OR, 0.97; p = 0.82; RRM2: OR, 0.94; p<0.0001) and the risk of progression increased (RRM1: HR, 1.02; p = 0.001; RRM2: HR, 1.005; p = 0.01). An interaction observed between BRCA1 and RRM1 allowed patients to be classified in three risk groups according to combinations of gene expression levels, with times to progression of 10.13, 4.17 and 2.30 months ( p = 0.001). Low BRCA1 expression was the only factor significantly associated with longer time to progression in 31 patients receiving cisplatin-based second-line therapy.