Chapter 21 In the News
Cancer Screening Tests
A good diagnostic test must find the early signs of the disease and must not provide false evidence of illness or miss the early signs in those who are sick. The tests cannot be too expensive or so unpleasant that no one wants to be screened.
Breast cancer screening focuses on mammograms that are recommended annually for
women over the age of 40. Yet mammograms miss as many as 30% of cancers in high-risk women who tend to have dense breasts. In June 2003 researchers reported that magnetic resonance imaging(MRI) detected 96% of tumors in high-risk women without symptoms. David Dershaw, director of breast imaging at MemorialSloanKeterringCancerCenter, says that only those who have a genetic marker for breast cancer or strong family history should have an MRI test done. If this test was done for the general population the vast majority of lesions found would be benign; which means a lot of unnecessary biopsies and anxiety.
Another test for breast cancer is ductal lavage, which is able to detect abnormal cells before they lump together to form a tumor in high-risk women. In this outpatient procedure a doctor anesthetizes the nipple then insets a flexible catheter into the breast ducts and flushes out cells. If the cells are precancerous, women can take steps to prevent the disease;this includes more frequent monitoring or taking the drug tamoxifen. Because many abnormal cells never turn into cancer this test is only recommended for those women who are at high risk.
There is no screening test for ovarian cancer at the present time. At the University of Kentucky Chandler Medical School, researchers have high hopes for a test called transvaginal ultrasound. The technique uses a narrow tampon-like probe inserted into the vagina to search out ovarian tumors. This technique has been studied for more than 15 years. In a group of 20,000 women age 50 or over with a family history of ovarian cancer, the test identified tumors in 29 women.
“In our view, it helps detect ovarian cancer, but larger trials are needed to prove that,” says John von Nagell, director of gynecology at University of Kentucky Chandler Medical Institute. (The ultra sound test is being studied in a large NCI study.)