['Minichromosome maintenance protein 2 (MCM2) is a component of the prereplicative complex. It is essential for eukaryotic DNA replication and is only expressed in proliferating cells. The prognostic utility of MCM2 compared with Ki-67, another marker of proliferating cells, on survival of patients with non-small-cell lung cancer (NSCLC) was studied.', 'We examined the immunohistochemical expression of MCM2 and Ki-67 in primary pathologic tumor specimens from 221 NSCLC patients. For each marker, the fraction of tumor cells with positive staining was assessed as a percentage and categorized into four groups: 0% to 24%, 25% to 49%, 50% to 74%, and > or = 75%. MCM2 and Ki-67 immunoreactivities were compared with each other, and associations with pathologic and clinical parameters predictive of survival were analyzed with the chi(2) test. Cox regression models were used to assess associations between MCM2 and Ki-67 and survival while controlling for confounders.', 'Independent variables significantly associated with survival were tumor stage, performance status, and staining category. Patients with less than 25% MCM2 immunoreactivity had a longer median survival time than patients with > or = 25% MCM2 immunoreactivity (46 v 31 months; P =.039) and a lower relative risk (RR) of death (RR, 0.55, 95% confidence interval, 0.34 to 0.88). There was no significant association between survival and Ki-67 expression.'] Is mCM2 an independent predictor of survival in patients with non-small-cell lung cancer?