CA125 regression in ovarian cancer patients treated with intravenous versus intraperitoneal platinum-based chemotherapy: a gynecologic oncology group study.

Objective: CA125 is a non-specific marker of peritoneal irritation which has the potential for false elevation during intraperitoneal treatment. The purpose of this study is to identify the rate of CA125 regression during intraperitoneal (IP) versus intravenous (IV) chemotherapy for ovarian cancer.

Methods: GOG 114, a randomized control trial evaluating IP and IV treatment, includes an intensive CA125 measurement schema with weekly CA125 levels until ≤ 35 units/ml for both IP- and IV-treated patients. Rate of CA125 normalization, median CA125 values for each treatment cycle, as well as clinical and pathologic features were compared between the treatment groups. Baseline CA125 levels and rate of CA125 decline were evaluated with respect to overall survival.

Results: CA125 data were available for 223 patients who received IV cisplatin/paclitaxel and for 231 patients who received IV carboplatin followed by IP cisplatin/paclitaxel. Standard prognostic criteria and baseline CA125 values were similar between the treatment groups. For treatment cycles in which IP-treatment was administered, there was no statistically significant difference in CA125 levels between IV- and IP-treated patients. The rate of CA125 normalization was similar between IV- and IP-treated patients (p=0.55). Patients with low pre-chemotherapy CA125 levels which rapidly declined during treatment demonstrated a survival advantage (p<0.0001).

Conclusions: No difference in CA125 decline was identified between IP- and IV-treated patients undergoing a weekly CA125 monitoring schedule. This data supports the utilization of standard CA125 response criteria in the therapeutic monitoring for patients receiving IP treatment.