RRM1 and non-small cell lung carcinoma: A recent meta-analysis of 18 studies evaluating a predictive role of RRM1 expression by IHC or quantitative real-time polymerase chain reaction (qRT-PCR) in the efficacy of gemcitabine-based regimens in patients with advanced NSCLC showed that low or negative RRM1 expression in advanced NSCLC was associated with higher response rate to gemcitabine-based regimens and a better prognosis [12].