In a groundbreaklng new study that is sure to inflame an ongoing debate, California researchers have recommended that women under the age of 50 need not undergo routine mammography screening when they have no symptoms or family history of the disease.
The study of nearly 32,000 asymptomatic women 30 and older found that although women under 50 have a significant rate of abnormal mammograms, far fewer actually have cancer compared to women over 50 with abnormal mammograms.
The report is the first to quantify how many women with abnormal readings actually have cancer after a diagnostic work-up--usually a biopsy--is completed, said the study's lead author, Dr. Karla Kerlikowske, an assistant clinical professor of epidemiology and biostatistics at UC San Francisco.
Mammography only suggests the possibility of cancer, Kerlikowske said.
"Our data indicate there are a lot of false positives with mammography. You have to consider the anxiety of having that (false positive) and all the procedures that go along with it," she said.
There is universal agreement on the need for yearly mammography for women 50 and older and among younger women with a family history of breast cancer.
Kerlikowske said she and her colleagues undertook their current research because of concern about the number of women under 50 who were told to get a mammogram and became anxious when the reading was abnormal.
"Once you have an abnormal mammography it's hard to ignore that. That's the problem with any of these screening tests; even if you know the risk of actually having cancer is incredibly small, once you have that positive test you are obligated to work it up," she said.
The study concluded that for every 1,000 women under age 50 having their first mammogram, 53 will have have an abnormal finding resulting in a total of 102 diagnostic procedures, including biopsies. These will result in the finding of two cancers, one of which will be invasive.
For 1,000 women age 50 and older undergoing their first mammography, 70 will have an abnormal finding, resulting in 132 additional procedures. Of these, 10 women will have cancer, with most of the cases being invasive cancer.
"Thus, women less than age 50 will have 2.6 times as many biopsies and three times as many diagnostic procedures for every cancer diagnosed compared to women age 50 and older," Kerlikowske said.
Younger women have high rates of false positives because their breast tissue is denser. As a woman ages, breast tissue becomes more fatty--and less dense--making it easier to detect an abnormal mass on a mammogram, she said. Breast cancer is the most common cancer in women and is responsible for 46,000 deaths per year in the United States.
The researchers also found that among women age 40 and older who have a family history of breast cancer--a mother, sister or daughter with the disease--80 of 1,000 undergoing a first screening will have an abnormal result and 14 of these will have cancer.
"Based on these data, we recommend that efforts to promote mammography screening be concentrated on all women age 50 and older, and on women ages 40 to 49 with a family history of breast cancer or who are otherwise at high risk for breast cancer," Kerlikowske said.
The recommendation matches one proposed by the National Cancer Institute in a report released in October. But the institute's report has been criticized by other health organizations, including the American Cancer Society.
In a news conference Monday in Washington, Cancer Society officials joined with 13 other major health groups to denounce the recommendation and advise women and their physicians to follow longstanding--and widely practiced--Cancer Society guidelines that recommend routine mammography every one to two years for women ages 40 to 50.
Cancer Society leaders and other health experts said Monday that the institute's proposal to back away from routine screening for women under 50 has caused confusion and may lead private insurers and governments to reduce coverage for mammography screening.
"This confusion might even have the effect of driving women of all ages away from a confidence in mammography," said Joann Schellenbach of the Cancer Society. "We're attempting to give advice to women and their physicians on how to deal with this and to speak to the potential policy ramifications, which would be horrible."
The Cancer Society was joined by the National Breast Cancer Coalition, the American Medical Assn., the American College of Obstetricians and Gynecologists and the American College of Radiology in its protest of the proposed institute guidelines. The groups also said they disagree with the proposal in the Clinton Administration's health reform plan that calls for mammography screening only every two years and only for women over 50.
"I do think women can get confused," said Dr. Suzanne W. Fletcher, chairwoman of the institute advisory panel that made the recommendations. "But I think most woman want to know the truth. This (UC San Francisco) study shows screening works better in older women and any women whose likelihood of cancer is higher."
Moreover, there is no conclusive data that screening women age 40 to 50 reduces breast cancer death rates, Fletcher said.
A better approach for women under age 50, Kerlikowske suggested, is for a doctor to advise a woman of her likelihood of having a false positive and what that might entail.
"The way things are done now, women (ages 35 to 50) are told, 'Go get your mammogram' rather than engaging the woman and deciding is this something she really wants to undertake," Kerlikowske said. "Our study suggests it should be more of a joint decision rather than, 'You must go do this.' "
In a study of nearly 32,000 women, California researchers found routine mammography screening to be beneficial for women over 50 and those over age 40 with a family history of the disease. Among women under age 50 with no such family history, the study found that routine mammography produced a significant rate of false positives--mammograms that showed an abnormality but later did not prove to be cancer.
Here are some results, per thousand women examined:
Number of Diagnostic Cancers abnormal procedures detected findings after abnormal finding Under 50/ First mammography 53 102 2 50 and older/ First mammography 70 132 10 Over 40/ First mammography (Family history) 80 NA 14
SOURCE: Dr. Karla Kerlikowske, UC San Francisco