Population screening is not currently available, as there is no evidence that it is justified. A small proportion of women may be screened in current randomised controlled clinical trials. Some selective investigation is available for women at increased risk because of a possible family predisposition.
Screening tests
Methods include imaging techniques such as abdominal or vaginal ultrasound, together with the estimation of blood tumour markers, such as CA125.
It seems that no single test is both sensitive and specific enough to screen for early-stage ovarian cancer. Combining tests, discovering more specific tumour markers and developing more specific imaging techniques may improve the prospects of screening for this cancer.
Ovarian cancer screening trials
UKCTOCS trial
The UK collaborative trial of ovarian cancer screening (UKCTOCS) began in January 2001. It aims to answer the question whether early detection of ovarian cancer will save lives. The study is also looking at the emotional, social and sexual effects of screening to detect ovarian cancer at an early stage in post menopausal women aged 50 to 74 in the general population. The cost implications of the screening methods to the NHS will also be assessed.
It is hoped that screening for ovarian cancer will prove helpful but it is important to see whether these benefits also have costs to women. The acceptability to women of the different types of screening is also being researched (29).
Recruitment closed in September 2005. There will be a six year follow up and the study will take ten years to complete. A total of 200,000 women have been randomised to receive either ultrasound screening or measurement of CA125; half are in the control group. Results of the trial will be expected in 2012 (following a five year follow up).
PLCO trial
The Prostate, Lung, Colorectal and Ovarian Screening Trial (PLCO) is a large scale clinical trial to determine whether certain cancer screening tests reduce death from cancer. For ovarian cancer women were given a transvaginal ultrasound (TVU) scan at initial visit and then 3 yearly and/or a CA125 test which was taken at their initial visit and then 5 yearly. The trial was opened in 1993 and enrollment was completed in 2001.
The long term objective of the PLCO trial is to determine whether screening with TVU and /or CA 125 decreases mortality in women ages 55 to 74. The preliminary results were published in the American Journal of Obstetrics and Gynecology in November 2005.
Of the 28,816 healthy women who underwent the initial (baseline) screening, 1338 (4.7%) had an abnormal TVU and 402 (1.4%) had an abnormal blood test. Thirty four women (0.1%) had abnormal results in both screening tests. Among the women with abnormal test results, 29 tumours were detected 20 of which were invasive.
Women who had an abnormal test result in one or both screening tests had a variety of diagnostic procedures to determine whether cancer was present, including 570 women who underwent a surgical procedure as follow up. Thus 541 women underwent surgery but did not have cancer.
The results published in this report reflect analysis of the initial baseline screenings for women enrolled between 1993 and 2001. However the results of subsequent years screening with TVU and CA 125 are not yet available, and it is these additional results that will ultimately determine whether this screening strategy is effective in reducing mortality from ovarian cancer. These results will not be available for several years. The PLCO is scheduled to collect data until 2008.
At the time of the baseline examination both TVU and CA 125 had low predictive values. This is a measure of how likely a person with a positive test result is to have the disease of interest when used to screen healthy women for ovarian cancer. Many investigators feel that an acceptable predictive value for ovarian screening tests is around 10%. The predictive values of these screening tests were 3.7% for an abnormal CA 125 test, 1% for an abnormal TVU, and 23.5% if both tests were abnormal. Although having an abnormality in both tests had a fairly high predictive value, only 9 of the 29 tumours (31%) found were associated with abnormalities in both tests (30).
Women at increased risk of ovarian cancer due to family history
The value of screening in women with a high risk of developing ovarian cancer is unknown. Between 5% and 10% of ovarian cancers are thought to be due to an inherited genetic mutation. Women with strong family histories of breast and ovarian cancer or mutations in BRCA1 or BRCA2 genes may have a 15-45% lifetime risk of developing the disease.
Investigation of those higher risk women is available by GP referral to genetics centres throughout the UK.
The UK Familial Ovarian Cancer Screening Study (UKFOCSS) is trying to find out whether ovarian screening is beneficial for women with strong family histories or mutations in BRCA1 or BRCA2 (31).
Families with two or more cases of ovarian cancer on the same side of the family, at any age (living or dead) may be entered by GPs on to the Cancer Research UK Familial Ovarian Cancer Register (FOCR). This is based at Addenbrookes Hospital in Cambridge. GPs can get advice from the FOCR about clinical management and centres where screening may be obtained (32).