ovarian cancer : Screening for ovarian cancer

Abstract
Ovarian cancer is the leading cause of death from gynaecological malignancies.

No precancerous lesions have been identified.

Bimanual examination has not been proven to be of value as a screening test.

Transvaginal ultrasound examination, with or without measurement of CA 125 levels, is currently being evaluated for population screening.

Women at high risk of ovarian cancer should be screened annually — with measurement of CA 125 level and transvaginal ultrasound examination.

Women with early-stage ovarian cancer have a 5-year survival rate of over 80%, suggesting that early detection may improve survival. To date, it has not been established whether benign (assessed histologically as non-invasive) or borderline ovarian tumours are premalignant. In the absence of a precancerous lesion, the goal of screening is the detection of preclinical disease.

Screening tests
A number of screening tests have been evaluated or are being evaluated currently. These include bimanual pelvic examination, ultrasound examination (Box), with or without colour Doppler flow imaging, and measurement of various circulating proteins.

Bimanual pelvic examination as part of a "well-woman's screen" has not been found to be useful.2

Ultrasound examination alone has neither sufficient specificity nor sufficient predictive value to justify its use in community screening, and it is expensive. It is currently not known whether the addition of Doppler flow imaging substantially improves the sensitivity of ultrasound alone.3

The usefulness of measuring the level of high-molecular-weight glycoprotein CA 125 as a screening test depends on the screening strategy, the cut-off value used and the population of women studied. It is of more benefit when used as part of a multimodal strategy.

In particular, screening by measuring CA 125 level and performing transvaginal ultrasound examination appears to provide the highest specificity and positive predictive value for the detection of ovarian cancer.4

Current trials
The CA 125 plus ultrasound screening strategy is currently on trial in the United Kingdom and the United States.

In the United Kingdom, CA 125 level plus transvaginal ultrasound examination versus transvaginal ultrasound alone versus no screening is being evaluated in 200 000 postmenopausal women. Quality of life, morbidity and cost-effectiveness are included in the evaluation.5 In the United States, the National Cancer Institute's Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening trial is comparing 37 000 women (aged 55–74) having annual measurement of CA 125 level and transvaginal ultrasound examination, with an equal number of women receiving their usual medical care.6 A large European multicentre trial involves 120 000 postmenopausal women randomly allocated to no screening, transvaginal ultrasound at intervals of 18 months, or transvaginal ultrasound at intervals of 3 years, for a total of 8 years.7 The results of these trials will provide evidence for whether screening provides a survival advantage, and whether this is at an acceptable financial cost. Other important issues, such as age of commencing and discontinuing screening and optimal screening intervals, will need to be established before implementing population-based screening for ovarian cancer.

by Cleola Anderiesz and Michael A Quinn