Chemosensitivity testing of irinotecan (CPT-11) in ovarian and endometrial carcinomas: a comparison with cisplatin.

Background: The tetrazolium dye (MTT) assay is useful in predicting chemosensitivity. Materials and Methods: Using an MTT assay, we designed an in vitro chemosensitivity test for irinotecan (CPT-11) and compared it with sensitivity to cisplatin in gynecologic carcinomas removed from 49 patients. Results: The mean tumor inhibition rate (I.R.: %) for irinotecan was relatively inferior to the I. R. for cisplatin in both ovarian and endometrial carcinomas /40.2 vs 53.2 and 43.5 vs 58.0] (p<0.05, respectively). In ovarian carcinomas, 13 (48.1%) of 27 cases were irinotecan-sensitive (I.R.≥50%) and 77% of the tumors were judged to be irinotecan and/or cisplatin-sensitive. There was no significant difference in the I.R. for irinotecan among the various histologic subtypes. Comparing in vitro sensitivity to irinotecan with clinical responses in 8 patients who received irinotecan, the overall accuracy of the MTT assay for evaluating clinical effectiveness was 75% (6 out of 8). In endometrial carcinomas, we found 9 (40.9%) out of 22 cases to be irinotecan-sensitive. The I.R. for irinotecan in G1 carcinomas [33.5] was significantly lower than in G2 carcinomas [59.3] (p<0.05). Conclusion: Our data suggest that irinotecan appears to have moderate antitumor activity in vitro against both ovarian and endometrial carcinomas and that differences in irinotecan sensitivity among the histologic subtypes were evident in the latter but not in the former.