CA125 decline in ovarian cancer patients treated with intravenous versus intraperitoneal platinum-based chemotherapy

To compare the slope of CA125 decline in patients with optimally debulked epithelial ovarian cancer achieving a response to intravenous (IV) versus intraperitoneal (IP) platinum-based chemotherapy. The secondary objectives are to determine if the time to normal CA125 levels and time to nadir of CA125 differ between the groups.

Patients with primary stage III, optimally cytoreduced ovarian cancer were stratified as to whether platinum and taxane chemotherapy was administered entirely IV (IV group), or whether it was given IV and IP (IP group). Inclusion criteria included an elevated CA125 prior to surgery or first cycle chemotherapy and at least 1 month follow-up after completion of chemotherapy. All patients had a complete or partial response. In addition, IP patients had to have received at least 1 cycle of IP chemotherapy. Because of the large range of CA125 levels, raw CA125 values were natural log transformed and compared using repeated measures analysis of variance (ANOVA).

53 patients met inclusion criteria, 36 in the IV arm and 17 in the IP arm. The median number of chemotherapy cycles was 6 in both groups; the range was 5-9 in the IP arm and 6-10 in the IV arm. The median CA125 prior to surgery was 888 (range 45-5940) in the IP group and 1081 (range 58-19,440) in the IV group, p=0.55. After surgery but prior to chemotherapy, the median CA125 was 175.5 in the IP arm (range 10.8-4035) versus 233.5 (range 16.5-6890) in the IV arm, p=0.43. The median time to normalization of CA125 for the IP group was half the time of the IV group, 0.75 months (range 0 to 4.5) versus 1.5 months (range 0 to 6.25), p=0.15. The time to nadir was slightly faster in the IP arm as compared to the IV arm, 4.5 months (2-10.5) versus 6 months (2-14), p=0.13. The CA125 slopes were parallel, indicating that the CA125 levels declined at the same rate in both groups. However, the patients treated with IP chemotherapy had significantly lower CA125 levels over all the cycles, p=0.02.

Contrary to the assumption that IP chemotherapy elevates CA125 levels due to peritoneal irritation, these results show a trend towards faster time to CA125 normalization and nadir, and significantly lower CA125 levels during therapy for patients responding to IP chemotherapy compared with patients responding to IV therapy.