Risk of diagnosis of ovarian cancer after raised serum CA 125 concentration: a prospective cohort study.

OBJECTIVE

To determine the risk of invasive epithelial ovarian cancer and fallopian tube cancer associated with a raised concentration of the tumour marker CA 125 in asymptomatic postmenopausal women.

DESIGN

Serum CA 125 concentration was measured annually in study participants for one to four years. Participants with a concentration > or = 30 U/ml were recalled for abdominal ultrasonography. Follow up was by annual postal questionnaire.

SETTING

General practice, occupational health departments, ovarian cancer screening unit in a teaching hospital.

SUBJECTS

22,000 volunteers, all postmenopausal women > or = 45 years of age; recruited between 1 June 1986 and 1 May 1990.

INTERVENTION

Surgical investigation if the ultrasound examination was abnormal.

MAIN OUTCOME MEASURES

Cumulative and relative risk of developing an index cancer (invasive epithelial cancer of the ovary or fallopian tube) after a specified CA 125 result.

RESULTS

49 index cancers developed in the study population during a mean follow up of 6.76 years. The overall cumulative risk of developing an index cancer was 0.0022 for the entire study population and was lower for women with a serum CA 125 concentration < 30 U/ml (cumulative risk 0.0012) but was appreciably increased for women with a concentration > or = 30 U/ml (0.030) and > 100 U/ml (0.149). Compared with the entire study population the relative risk of developing an index cancer within one year and five years was increased 35.9-fold (95% confidence interval 18.3 to 70.4) and 14.3-fold (8.5 to 24.3) respectively after a serum CA 125 concentration > or = 30 U/ml and 204.8-fold (79.0 to 530.7) and 74.5-fold (31.1 to 178.3) respectively after a concentration > or = 100 U/ml.

CONCLUSION

CA 125 is a powerful index of risk of ovarian and fallopian tube cancer in asymptomatic postmenopausal women.