There has been a lot of research to develop a screening test for ovarian cancer, but there hasn’t been much success so far. The two tests used most often to screen for ovarian cancer are a transvaginal ultrasound (TVUS) and the CA-125 blood test.
TVUS is a test that uses sound waves to look at the uterus, fallopian tubes and ovaries by putting an ultrasound wand into the vagina. It can help find a mass (tumor) in the ovary, but it can’t actually tell if a mass is cancer or benign. When it is used for screening, most of the masses found are not cancer.
CA-125 is a protein in the blood. In many women with ovarian cancer, levels of CA-125 are high. This test can be useful as a tumor marker to help guide treatment in women known to have ovarian cancer because a high level often goes down if treatment is working.
But checking CA-125 levels has not been found to be as useful as a screening test for ovarian cancer. The problem with using this test for screening is that common conditions other than cancer can also cause high levels of CA-125.
The combined results of two ovarian cancer screening trials suggest that a personalized strategy involving frequent screening of high-risk women could improve the chance that tumors are detected at early stages when they are easier to treat.
As reported in a paper published in the journal Clinical Cancer Research, these trials imply that a protocol involving quarterly blood test to identify significant increases above each patient’s personal baseline in levels of the protein CA125, followed by ultrasound examination when such elevations are detected, could reduce the risk of diagnosis with advanced cancer in high-risk women who choose to delay recommended preventive surgery.
“The standard advice for women at high risk of ovarian cancer, due to either family history or inherited gene mutations, is to have their ovaries and fallopian tubes removed once their families are complete. Some women choose to postpone this surgery,” says Steven Skates, Ph.D., of the Massachusetts General Hospital (MGH) Cancer Center and the Biostatistics Unit, co-lead and corresponding author of the report. “Our screening protocol increased the proportion of tumors detected at early stages from 10 percent – which is typically seen in high-risk women who are not screened – to 50 percent.”
CA125 levels are known to be raised over the level of 35 in the blood of most women with ovarian cancer. While screening for raised CA125 and/or transvaginal ultrasound may be considered for high-risk women who postpone surgery that approach has not been shown to improve patient outcomes.
The two trials reported in the current paper utilize the Risk of Ovarian Cancer Algorithm (ROCA) – co-developed by Skates and Ian Jacobs, MD, FRCOG, of the University of New South Wales in Australia and University College London, which tracks CA125 levels over time to identify significant elevations above each patient’s baseline levels, even those that do not exceed the traditional threshold of 35.
Another study, the UK Familial Ovarian Cancer Screening Study, led by ROCA co-developer Jacobs and published in the journal Clinical Oncology, found that a similar protocol using ROCA, based testing every four months was also better than current practice at diagnosing early, stage tumors in high-risk women.
Skates notes that a formal analysis of the data from all three trials could increase the statistical power of these studies and could lend stronger support to recommending frequent ROCA-based screening for high-risk women who choose to postpone surgery or while waiting for surgery.