Prevalence of ovarian cancer among women with a CA125 level of 35 U/ml or less

Abstract

Background: The optimal upper limit of the normal range for CA125 in ovarian cancer screening is unknown. We investigated the prevalence of ovarian cancer among women in the Shizuoka Cohort Study on Ovarian Cancer Screening (SCSOCS) trial who had an abnormal ultrasound (US) and a CA125 level of 35 U/ml or less.

Methods: Of 48,027 women enrolled in the SCSOCS trial, 40,801 women never had a CA125 level of more than 35 U/ml, and underwent transvaginal US.

Results: Among the 40,801 women (age range 45-85 years), 4,859 women had an abnormal transvaginal US examination (category 1 [simple morphology], 4,741 women, and category 2 [complex morphology], 118 women). Of the 4,859 women, 981 (912 with the category 1 and 69 with the category 2) had a surgery. Of the 981 women, ovarian cancer was diagnosed in 8 (0.815%), and 5 of these 8 cancers (63%) were in stage I. The prevalence of ovarian cancer with abnormal US was 0.207% among women with a CA125 level of up to 15 U/ml, 0.488% among those with values of 15-20 U/ml, 0.685% among those with values of 20-25 U/ml, 2.04% among those with values of 25-30 U/ml, and 6.12% among those with values of 30-35 U/ml.

Conclusions: Surgery-detected ovarian cancer is not rare among women with CA125 levels of 35 U/ml or less - levels generally thought to be in the normal range.