Defining response of ovarian carcinoma to initial chemotherapy according to serum CA 125

Abstract

Purpose: To produce definitions based on serial CA 125 levels to measure response of ovarian carcinoma in patients receiving first-line chemotherapy.

Patients and methods: Definitions were derived from analysis of 277 patients in North Thames Ovary Trial 3. Patient data were then incorporated into a computer program and tested against 254 patients in North Thames Ovary Trial 4 and 458 patients in Gynecologic Oncology Group (GOG) protocol 97. For optimum detection of response, three response definitions have been combined into a computer program. The precise definitions use mathematic logic and take account of factors such as intervening samples. Response to a specific treatment has occurred if after two samples there has been a 50% decrease, confirmed by a fourth sample (50% response), or a serial decrease over three samples of greater than 75% (75% response). The final sample has to be at least 28 days after the previous sample.

Results: Six hundred twenty of 989 patients were considered assessable for response according to CA 125 level. Only two patients (0.3%) had a CA 125 response at the time of clinical progression. The CA 125 response rate was 62% and 54% in the North Thames trials. In the GOG trial, it was 66% in all 317 patients assessable for CA 125 and 67% in 221 patients whose CA 125 level was not measurable according to GOG criteria, compared with a GOG-defined response rate of 62%. The sensitivity for detecting GOG-defined response was at least 68%.

Conclusion: Definitions based on a 50% or 75% decrease of CA 125 levels have been shown reliably to define partial response of ovarian cancer in patients receiving first-line chemotherapy. These definitions should be used in addition to or instead of standard response criteria.