Better early test needed for ovarian cancer
Ovarian cancer kills an estimated 15,000 women each year in the United States. Another 140,000 women worldwide die from ovarian cancer each year. Most of these deaths are due to cancers which are found after the cancer has spread. Better early tests are needed to find ovarian cancer earlier when it is easier to treat.
Researchers from Stanford University School of Medicine and the non-profit Canary Foundation have published a study today in the open access journal Public Library of Science which looks at the unsuspected “occult” serous cancers discovered in a small fraction of apparently healthy women who have undergone prophylactic bilateral salpingo-oophorectomy (PBSO).
Ovarian cancer is difficult to diagnosis early as the symptoms are not obvious and are often vague. The symptoms include:
- Pressure or pain in the abdomen, pelvis, back, or legs
- A swollen or bloated abdomen
- Nausea, indigestion, gas, constipation, or diarrhea
- Feeling very tired all the time
Often these symptoms don't manifest until the tumor is already several centimeters in diameter. The researchers looked at the estimated time it takes for an occult cancer to become a larger, easily detected cancer. They estimate serous ovarian cancers spend more than 4 years as in situ (a very early stage of cancer development), stage I, or stage II cancers. Serous ovarian cancers then spend another year as stage III and IV cancers before they become clinically apparent.
The overall five year survival rate for ovarian cancer is only 46 per cent (it is lower for more advanced stages), but if the diagnosis is made before the tumor has spread, the five year survival rate is nearer 93 per cent. The researchers feel that tests are needed which may find the ovarian tumors early when the tumor is smaller than 1 cm in diameter. Current tests can’t do that.
Current tests for ovarian cancer look for abnormally high levels of protein in normal blood which the smaller tumors don’t make. So far no ovarian cancer-specific protein or other biomarker has been identified that could be used to develop a test that comes anywhere near this level of performance.
Identification of truly ovarian cancer-specific biomarkers or novel strategies will be needed in order to take advantage of the window of opportunity.
The Preclinical Natural History of Serous Ovarian Cancer: Defining the Target for Early Detection; PLoS Medicine, PLoS Med 6(7): e1000114, Open Access, July 2009; doi:10.1371/journal.pmed.1000114; Patrick O Brown and Chana Palmer
American Cancer Society
National Cancer Institute