Ovarian cancer is not usually detected in early stages because there are no adequate screening tests. Pelvic exams are not sensitive enough to detect most early cases of ovarian cancer. CA-125 is a blood test that measures proteins that are usually elevated in women with advanced ovarian cancer. However, researchers estimate about 50 percent of women with early stage ovarian cancer will have a normal CA-125 test result. In addition, elevated levels of CA-125 can also be caused by many other conditions.
Tumors need a blood supply to get nourishment. When a solid cancer develops, it uses a process, called angiogenesis, to spur the growth of new capillaries (tiny blood vessels) that feed the tumor and transport waste products for elimination. The new capillaries are "leaky," allowing stray cancer cells to pass through the vessel walls into the surrounding tissue, where they can continue to grow outside the tumor.
Researchers believe the presence of abnormal, leaky capillaries may be a good indication of the presence of ovarian cancer. Thus, detection of the vessels through imaging techniques may serve as a useful diagnostic or screening tool for ovarian cancer.
Currently, some doctors use a transvaginal ultrasound to get pictures of the ovaries that may suggest abnormalities. However, standard ultrasound machines are still not able to see blood flow in the tiny capillaries feeding the tumor.
Some doctors are now testing a new technique for ovarian cancer detection, called microvascular sonography. First, the patient is given an intravenous infusion of a contrast agent. Then doctors use high resolution transvaginal ultrasound to image the ovary. The contrast agent is in the form of microbubbles that can flow freely through the tiniest of blood vessels. If ovarian cancer is present, doctors will be able to see the contrast agent as it flows through the tumor capillaries.
Currently, microvascular sonography is being tested at New York University Cancer Institute and Vanderbilt University. Doctors will attempt to reproduce the results of the technique in 100 women who are having surgery to remove an ovarian mass (not necessarily cancer). The ultrasound technique will be performed to evaluate the efficacy of the technique in detecting ovarian cancer. Then a biopsy will be performed to look for the presence of cancer and confirm the imaging results.
David Fishman, M.D., a Gynecologic Oncologist with NYU Cancer Institute, says the current trial should be complete by this year or next. After that, researchers hope to confirm the results using a larger study of 1,000 women at various sites throughout the country. Fishman says the ultrasound equipment used in the study is already widely available and the contrast agents are currently used for heart imaging studies. So if the test proves to be accurate, it could potentially be a widely available breakthrough in ovarian cancer detection. Eventually, he says it may become part of the standard annual exam for women.
The test may especially be useful for women who are at high risk for ovarian cancer, allowing them to be screened before opting to have their ovaries removed to prevent the cancer.
For information on the study, log onto http://www.clinicaltrials.gov . Then type the trial identification number in the search box: NCT00531570.