Assessing the malignant potential of ovarian inclusion cysts in postmenopausal women within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS): a prospective cohort study.

OBJECTIVE: To evaluate the malignant potential of ultrasound-detected ovarian inclusion cysts in the development of ovarian cancer (OC) in postmenopausal women. DESIGN: Prospective cohort study. SETTING: UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). POPULATION: Postmenopausal women. METHODS: In UKCTOCS, women in the ultrasound group have annual scans. Women with inclusion cysts (single/multiple anechoic ≤10-mm ovarian cysts) and normal ovaries (both uniform hypoechogenicity) on their first scan were identified and followed up through cancer registry/questionnaires. MAIN OUTCOME MEASURES: Relative risk (RR) of developing OC, invasive epithelial ovarian cancer (iEOC), breast cancer (BC) and endometrial cancer (EC) in women with inclusion cysts relative to those with normal ovaries. The incidence was compared with UK age-adjusted expected rates (Office for National Statistics, 2005). RESULTS: Postmenopausal women (n = 48,230) attended the year 1 (11 June 2001-6 December 2006) screen; 1234 (2.5%) had inclusion cysts alone and 22,914 had normal scans. By 1 November 2009 (median follow-up, 6.13 years; interquartile range, 4.96-6.98 years), four, three (one Type II), seven and 22 women with inclusion cysts and 32, 29 (20 Type II), 90 and 397 women with normal ovaries were diagnosed with OC, iEOC, EC and BC, respectively. The RR values for the respective cancers (OC [RR, 2.32; confidence interval [CI], 0.86-6.28], iEOC [RR, 1.92; CI, 0.62-5.92], EC [RR, 1.44; CI, 0.68-3.05], BC [RR, 1.12; CI, 0.73-1.73]) were not increased. There was no difference between the observed versus expected incidence rates for these cancers in women with inclusion cysts. CONCLUSIONS: Postmenopausal women with ultrasound-detected inclusion cysts do not seem to be at increased risk of ovarian or breast/endometrial (hormone-dependent) cancers.