Benign ovarian cysts and ovarian cancer: a cohort study with implications for screening

Background Whether some benign ovarian cysts can develop into cancerous cys ts is not known. If a large proportion of ovarian cancers arose in this way , it might be possible to remove the benign cysts in a screening programme before they became malignant. We used follow-up data from a cohort of 5479 self-referred women without symptoms, who participated in a ultrasonographi c-screening trial for early ovarian cancer between June, 1981, and August, 1987. We assessed whether the removal of persistent ovarian cysts from thes e women was associated with a reduction in the expected number of deaths fr om ovarian cancer in the cohort as a whole. Methods The expected number of deaths from all causes, all cancers, and ova rian. breast. and colorectal cancers were calculated for the study cohort b y the standard life-table method. The actual number of deaths and each caus e were obtained and the proportional mortality ratio was calculated for eac h cause of death. Findings 5135 (95%) of the participants in the original trial were traced. During the screening, five of these women were found to have stage I epithe lial ovarian cancer and 88 had benign epithelial ovarian tumours. The numbe r of reported deaths from all causes (387 [50% of expected]), ail cancers ( 221 [71%]), and ovarian cancer (22 [90%]) was lower than expected because o f the "healthy-volunteer effect". Proportional mortality ratios were 100% ( by definition) for all cancers. 141% for breast cancer, 128% for ovarian ca ncer (95% CI 87.7-187.6, p=0.19), 84% for colorectal cancer, and 48% for lu ng cancer. Interpretation The removal of persistent ovarian cysts was not associated w ith a decrease in the proportion of expected deaths from ovarian cancer rel ative to other cancers during follow-up. For population-based screening of healthy women without a family history of ovarian cancer, a screening test is required that is specific and sensitive to early malignant disease. and inexpensive.