Large Prospective Study of Ovarian Cancer Screening in High-Risk Women: CA125 Cut-Point Defined by Menopausal Status

Abstract

Previous screening trials for early detection of ovarian cancer in postmenopausal women have used the standard CA125 cut-point of 35 U/mL, the 98th percentile in this population yielding a 2% false positive rate, whereas the same cut-point in trials of premenopausal women results in substantially higher false positive rates. We investigated demographic and clinical factors predicting CA125 distributions, including 98th percentiles, in a large population of high-risk women participating in two ovarian cancer screening studies with common eligibility criteria and screening protocols. Baseline CA125 values and clinical and demographic data from 3,692 women participating in screening studies conducted by the National Cancer Institute-sponsored Cancer Genetics Network and Gynecologic Oncology Group were combined for this preplanned analysis. Because of the large effect of menopausal status on CA125 levels, statistical analyses were conducted separately in pre- and postmenopausal subjects to determine the impact of other baseline factors on predicted CA125 cut-points on the basis of 98th percentile. The primary clinical factor affecting CA125 cut-points was menopausal status, with premenopausal women having a significantly higher cut-point of 50 U/mL, while in postmenopausal subjects the standard cut-point of 35 U/mL was recapitulated. In premenopausal women, current oral contraceptive (OC) users had a cut-point of 40 U/mL. To achieve a 2% false positive rate in ovarian cancer screening trials and in high-risk women choosing to be screened, the cut-point for initial CA125 testing should be personalized primarily for menopausal status (50 for premenopausal women, 40 for premenopausal on OC, and 35 for postmenopausal women).