Purpose: To assess CA-125 as a measure of response in patients treated with paclitaxel.
Patients and methods: One hundred forty-four patients treated with paclitaxel derived from four different trials and 625 patients treated with platinum from two trials were analyzed using precisely defined 50% and 75% reductions in CA-125. The standard and CA-125 response rates to paclitaxel and platinum were compared. In addition, we analyzed individual patient groups in which there was a difference in response according to the two response criteria.
Results: Patients with stable disease as determined by standard criteria who were treated with platinum and responded according to CA-125 criteria have an improved median progression-free survival compared with patients with stable disease who did not respond according to CA-125 criteria (10.6 v 4.8 months; P<.001). Standard and CA-125 response rates for patients treated with platinum (58.93% v 61.31%, respectively) and paclitaxel (30.65% v 31.67%, respectively) were very similar, as were rates of false-positive prediction of response by CA-125 (platinum 2.2% and paclitaxel 2.9%). Responders to paclitaxel had a significantly improved progression-free survival compared with non-responders by both standard criteria (median progression-free survival, 6.8 v 2.5 months; P<.001) and CA-125 criteria (median progression-free survival, 6.8 v 3.4 months; P<.001).
Conclusion: Forassessing activity of therapy for ovarian cancer, these data show that precise 50% or 75% CA-125 response criteria are as sensitive as standard response criteria. We propose that they may be used as a measure of response in lieu of or in addition to standard response criteria in clinical trials involving epithelial ovarian cancer. Sensitivity is maintained whether patients are treated with platinum or paclitaxel.