The role of transvaginal ultrasound in screening for ovarian cancer.

Ovarian cancer is a low-prevalence postmenopausal cancer with a high mortality rate and is the fifth most lethal cancer in women. The most common serous subtype with TP53 mutations spreads rapidly throughout the peritoneal cavity (stage III/IV) when 5-year survival is 10%. If diagnosed while confined to the ovary (stage I), the survival rate exceeds 90%. This is the rationale for screening. Annual transvaginal ultrasound (TVU) scans used as a primary screening modality or as a second-line test following primary screening with serum CA125 (multimodal) have been investigated in several trials. Only two large randomized controlled trials have provided mortality data. The US Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial studied over 78 000 women (randomized to screening with either TVU or CA125, or control) over 6 years with 14 years follow-up and found no mortality benefit from screening and increased morbidity in the screened arm. The UK Collaborative Trial of Ovarian Cancer Screening studied over 202 000 women randomized to TVU, multimodal or control in a 1 : 1 : 2 ratio over 7-11 years with 11 years follow-up. CA125 was interpreted by the Risk of Ovarian Cancer algorithm which identifies a rise in the level rather than a fixed cut-off. There was a late reduction in mortality after 7 years in the screened arm (23% in the multimodal arm and 21% in the TVU arm), but the overall reduction was not significant. Further follow-up may reveal whether TVU has a primary or secondary role in ovarian cancer screening.