Ovarian cancer is the leading cause of death from gynaecological cancers in the UK. This is related to diagnosis at advanced stage. When women are diagnosed earlier, they have a much better survival – over 90% of Stage I patients are alive five years after diagnosis compared to 4% of Stage IV patients. This suggests that screening may help save lives by detecting the disease earlier.

The United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) was designed to test this hypothesis. Between April 2001-Sept 2005, 202,638 postmenopausal women, aged 50-74 years were recruited through 13 trial centres in England, Wales and Northern Ireland. Women were randomly allocated to one of three groups (i) control (C) - no screening (ii) multimodal screening (MMS) - annual blood test for serum CA125 measurement. The results were interpreted using the ‘Risk of Ovarian Cancer Algorithm’, with transvaginal ultrasound as a second line test in case of abnormality (iii) ultrasound screening (USS) – annual and second line tests were transvaginal scans.

Women in the screen arms underwent a total of 673,765 annual screens till 31 December 2011. Following censorship on 30 June 2020, at a median follow-up of 16.3 years per woman, the final mortality analysis was undertaken. The final results published in The Lancet showed that compared to the no screening group, there was a 39% increase in the incidence of women diagnosed with Stage I and II ovarian and tubal cancer and a 10% decrease in incidence of those diagnosed with Stage III and IV disease in the multimodal group. There was no difference in stage in the ultrasound group compared to the no screening group. There was however no reduction in deaths due to ovarian and tubal cancer in the multimodal or the ultrasound group compared to the no screening group.

The reduction in stage III and IV incidence in the multimodal group was not sufficient to translate into lives saved. This illustrates the importance of specifying cancer deaths as the primary outcome in screening trials. Given that screening did not reduce ovarian and tubal cancer deaths, currently general population screening cannot be recommended.

Participants donated their samples and data for secondary research studies. Hence follow-up of the cohort will continue till 2024.