The expression of Ki-67, but not proliferating cell nuclear antigen, predicts poor disease free survival in patients with adenocarcinoma of the lung.BACKGROUND:Ki-67 expression has been established as a predictive marker for recurrence in breast cancer, and proliferating cell nuclear antigen (PCNA) which is also a proliferation marker, is also herein discussed regarding its role in the prognosis of various types of cancer. However, no useful data are presently available regarding the biological significance of both molecules in lung cancer.PATIENTS AND METHODS:Tumor specimens were collected from 183 consecutive patients who underwent a complete resection for lung adenocarcinoma from 2003 to 2007 in our Department. We analyzed the Ki-67 and PCNA expression levels in primary lung adenocarcinoma by immunohistochemistry.RESULTS:Positive expression of Ki-67 and PCNA was identified in 41 (22.4%) and 149 (81.4%) patients, respectively. The positive expression of Ki-67 was identified in 14 (50.0%) out of 28 patients and 27 (18.1%) out of 155 patients with and without recurrence, respectively (p<0.001). PCNA expression was not correlated with recurrence. Positive expression of Ki-67 was associated with a poorer disease-free survival according to the survival analysis. A multivariate analysis also demonstrated that Ki-67 expression was independently associated with an increased risk of poor disease-free survival.CONCLUSION:Ki-67 may be a useful marker for predicting postoperative recurrence in patients with non-small cell lung cancer following complete resection.