Screening for ovarian cancer by monitoring cancer antigen 125 (CA-125) needs further assessment

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11 January 2016

The large UK Collaborative Trial of Ovarian Cancer Screening in post-menopausal women has three arms. We described the multimodal screening arm of the trial (CA-125 monitoring followed by vaginal ultrasound examination when indicated) in a News Article on 19 May 2015. Multimodal screening was shown to correctly assess as not at risk 99.8% of women who did not have ovarian cancer and also correctly identified 86% of those women who did.

The UK Collaborative Trial has now reported online in the Lancet on 17 December 2015 results from the other two arms of the trial: women who were screened by ultrasound scan alone and a control group who were not screened, together with the most important factor for a cancer screening program: the number of lives saved.

After a follow-up time of up to14 years, outcome was assessed in more than 100,000 women who were not screened, more than 50,000 women who had multimodal screening and more than 50,000 who had ultrasound screening alone. Compared with those who were not screened, there were 15% fewer deaths in those who had multimodal screening and 11% fewer in those who had ultrasound alone, but statistical analysis showed that these results could have occurred by chance.

 However, the researchers had pre-specified a secondary analysis that excludes women whose sequential CA-125 results indicate that they already had ovarian cancer at the time of recruitment to the trial. This showed that multimodal screening with CA-125 monitoring followed by ultrasound gave a significant 20% average reduction in mortality, rising from a reduction of 8% in the first seven years to 28% in years eight to fourteen.

The researchers interpreted their results as showing that further follow-up was needed to assess the extent of the mortality reduction before firm conclusions can be reached on the long-term efficacy and cost-effectiveness of ovarian cancer screening. Professor Usha Menon, trial co-ordinator at University College London,  said they would continue to follow the patients for what is expected to be another three years to confirm whether there is a benefit.

The research was funded by the Medical Research Council, Cancer Research UK, the Department of Health and the Eve Appeal.