Labeling indices of human lung cancer. Correlation with histologic type and survival.

The labeling index (LI) of tumor specimens from 28 patients (9 primary, 21 metastases) with lung cancer was analyzed after in vivo 3H-thymidine labeling. The mean LI was 11.1 (range, 1.4 to 37.6), and the median was 10.6. The average LI for adenocarcinoma (1.8) was significantly lower than those of small-cell, large-cell and poorly differentiated epidermoid carcinoma (12.8, 11.5 and 13.6, respectively). The variation in LI from site to site was less than 50% in 72% of lesions. Among the nonadenocarcinomas, no significant differences in average LI were observed between primary and metastatic tumors. For 17 previously untreated patients, mean survival times for patients with tumors whose LIs were below and above the mean were 63 and 30 weeks, respectively (0.10 greater than P greater than 0.05).