Ovarian cancer risk among older patients with stable adnexal masses.

BACKGROUND: Few studies have evaluated the risk of cancer among older patients with stable adnexal masses in community-based settings to inform the duration of observation time needed.

OBJECTIVE: To assess ovarian cancer risk among older patients with stable adnexal masses on ultrasound.

STUDY DESIGN: Retrospective cohort study of patients in a large community-based health system, aged > 50 years with an adnexal mass < 10 cm on ultrasound between 2016-2020 who had at least one follow-up ultrasound done > 6 weeks following initial ultrasound. Masses were considered stable on follow-up exam if they did not exhibit an increase of > 1 cm in greatest dimension nor a change in standardized reported ultrasound characteristics. Ovarian cancer risk was determined at increasing time intervals of stability following initial ultrasound.

RESULTS: Among 4061 patients with stable masses, the average age was 61 years (range 50-99 years) with an initial mass size of 3.8 cm (range 0.2-9.9 cm). With a median follow-up of 3.7 years, 11 cancers were detected for an absolute risk of 0.27%. Ovarian cancer risk declined with longer duration of stability, from 0.73 (0.30-1.17) per 1000 person-years at 6-12 weeks, 0.63 (95% CI, 0.19-1.07) at 13-24 weeks, 0.44 (95% CI, 0.01-0.87) at 25-52 weeks, and 0 at > 52 weeks. Expressed as number needed to re-image, ongoing ultrasound imaging would be needed for 369 patients whose masses show stability at 6-12 weeks, 410 patients at 13-24 weeks, 583 patients at 25-52 weeks, and > 1142 patients with stable masses at 53-104 weeks to detect one case of ovarian cancer.

CONCLUSIONS: In a diverse community-based setting, among patients 50 years and older with an adnexal mass that was stable for at least 6 weeks after initial ultrasound, the risk of ovarian cancer was very low at 0.27%. Longer demonstrated duration of stability was associated with progressively lower risk, with no cases observed after 52 weeks of stability. These findings suggest that the benefit of ultrasound monitoring of stable masses beyond 12 months is minimal and may be outweighed by potential risks of repeated imaging.