Mitotic index does not predict prognosis in stage IA non-small cell lung cancer

Despite radical resection, many patients with stage IA non-small cell lung cancer (NSCLC) die of metastatic disease, showing that apparently there were already micrometastases at the time of surgery. To identify patients at risk for metastatic disease, accurate prognostic factors are needed. Because the mitotic activity index (MAI) is of good prognostic value in several other cancers, we assessed its value in stage IA NSCLC. We assessed the MAI in the sections of 133 patients with radically resected stage IA NSCLC. MAI, histologic subtype, age, sex, location of tumor, type of surgery and tumor diameter were correlated with survival. The mean MAI was 29, ranging from 0 to 89. MAI was not correlated to histologic tumor type or lymph node sample procedure, or any of the other clinicopathologic features. No correlation was found between MAI and survival. Univariate analysis showed that only age was a significant predictor of survival (P=0.0007). This was confirmed by multivariate analysis. The mitotic index is not a predictor of prognosis in stage IA NSCLC. Therefore other prognostic factors have to be investigated.