Ovarian Cancer Test Spots Tumors Earlier
But Cost, Process Might Keep it From Widespread Use
Nov. 19, 2002 -- A new, high-tech blood test may help detect ovarian cancer much earlier than current methods and help improve survival rates for the usually silent killer. The test uses digital analysis of DNA to pinpoint the abnormal cells shed by cancerous tumors and may eventually be used to screen for other types of cancer as well.
Results from initial studies of the test appear in the Nov. 20 issue of the Journal of the National Cancer Institute.
According to the American Cancer Society, ovarian cancer is the fifth leading cause of cancer death among women; about 23,300 new cases are diagnosed in the U.S. each year.
The chances of survival are much greater if the cancer is caught in its early stages -- before it has spread to other organs. But there are currently no practical ways to screen all women for early ovarian cancer.
"There is a huge need for an effective screening tool for ovarian cancer," says Elizabeth Poynor, MD, surgical oncologist at Memorial Sloan-Kettering Cancer Center in New York. "The main problem with ovarian cancer is that more than 75% of the cancers picked up are among women in advanced stages of disease where the cure rate is only about 20%. But if the cancer is picked up early, the cure rate is about 95% to 98%."
The new test is based on digital analysis of DNA fragments. Cells have two copies of each gene in the body. In normal cells, these two copies are balanced and form the building blocks for healthy cells. But cancerous cells have an unbalanced ratio of these two gene copies. The digital test works by counting the copies in each blood sample and looking for irregularities.
For the study, researchers tested 54 blood samples from women with early- and late-stage ovarian cancer. The digital analysis detected the genetic imbalance in 87% of early-stage cancer patients and in 95% of late-stage patients. No such imbalances were found in blood samples from 31 healthy individuals.
This DNA analysis "appears to detect ovarian cancers very well and is far more precise than other available tests, says study researcher le-Ming Shih, MD, PhD, pathologist at the Kimmel Cancer Center at Johns Hopkins Medical Institutions, in a news release.
For now, Shih concedes that this test is far too expensive and labor-intensive to make it a viable option for general cancer screening for all women. But he says that it might be useful in screening women at high risk.
Poynor says this DNA test is an example of a new way to look at lots of things in a single blood sample rather than just one, as with conventional screening tests. A similar approach being studied by FDA researchers looks at several types of proteins in the blood that may be a marker for ovarian cancer.