MCM2 is an independent predictor of survival in patients with non-small-cell lung cancer

Purpose: 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 co mpared with Ki-67, another marker of proliferating cells, on survival of pa tients with non-small-cell lung cancer (NSCLC) was studied. Patients and Methods: We examined the immunohistochemical expression of MCM 2 and Ki-67 in primary pathologic tumor specimens from 221 NSCLC patients. For each marker, the fraction of tumor cells with positive staining was ass essed as a percentage and categorized into four groups: 0% to 24%, 25% to 4 9%,50% to 74%, and greater than or equal to 75%. MCM2 and Ki-67 immunoreact ivities were compared with each other, and associations with pathologic and clinical parameters predictive of survival were analyzed with the x(2) tes t. Cox regression models were used to assess associations between MCM2 and Ki-67 and survival while controlling for confounders. Results: 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 patie nts with greater than or equal to 25% MCM2 immunoreactivity (46 v31 months; P = .039) and a lower relative risk (RR) of death (RR, 0.55, 95% confidenc e interval, 0.34 to 0.88). There was no significant association between sur vival and Ki-67 expression. Conclusion: Immunostaining of tumor cells for MCM2 is an independent progno stic parameter of survival for patients with NSCLC. Interpretable results c an be obtained on more than 96% of paraffin-embedded specimens, and approxi mately 35% will be in the favorable subgroup, with less than 25% positively stained tumor cells. Whether MCM2 is predictive of response to therapy nee ds to be studied.