Although mammography for women in their 50s and 60s can reduce deaths from breast cancer by nearly a third, the technique provides no measurable improvement in survival among younger women, according to UC San Francisco researchers.
Breast cancer screening for women under 50 has been a hotly debated subject because previous studies of its efficacy have been small and yielded mixed results. Reflecting that confusion, the American Medical Assn. and the American Cancer Society have recommended mammography for women in their 40s, while the National Cancer Institute has not.
Dr. Karla Kerlikowske and her colleagues at UC San Francisco attempted to overcome that problem by combining the data from 13 studies completed between 1966 and 1993.
They report today in the Journal of the American Medical Assn. that the new analysis shows that mammography "does not significantly reduce mortality in women aged 40-49 years." The study also concludes that, in older women, a mammogram every other year is just as effective as a yearly examination.
"To everyone who looks at it from a scientific viewpoint, (the question of mammography before age 50) is a closed issue," said Dr. Herman Kattlove, who heads a RAND group studying another aspect of breast cancer.
Both Kerlikowske and Kattlove emphasized, however, that the debate over screening younger women applies only to the general population and not to women with a high family risk of breast cancer. Such women, Kattlove said, "ought to have mammography screening at earlier ages."
Neither the AMA nor the American Cancer Society is backing down from their positions. "Because of the complexity of the issues involved, the variation in design and conduct of the studies cited, (and) the fact that most of the studies cited were conducted in countries other than the United States (where mammography technology is not as advanced as in the United States) . . . these reviews should not be used alone as the basis for denying screening mammograms to women aged 40-49," said Dr. James Allen, vice president of science, technology and public health standards for the AMA.
A cancer society spokesman said the agency had "actively reviewed" the same studies gathered in the UC San Francisco paper and found no reason to change its recommendations.
Breast cancer strikes about 180,000 women each year, killing 46,000. In a meeting of the National Cancer Advisory Board in Washington on Tuesday, Samuel Broder, head of the National Cancer Institute, said the number of breast cancer deaths declined 6% from 1989 to 1992--the largest short-term drop since 1950--largely because of better treatment and more women being screened.
In a separate study in the same journal, the team at RAND in Santa Monica offered its outline for the optimum cost-effective program for detecting and treating breast cancer based on "the best available scientific information."
The team, headed by Kattlove, said the program should include screening every other year for women in their 50s and 60s, mastectomy or breast-conserving surgery with radiation to remove tumors, chemotherapy after surgery and only routine surveillance after surgery.
More sophisticated imaging procedures for detecting recurrence, as well as mammography for women under 50 and over 70, simply add to costs without saving any lives, Kattlove said.
The shortcomings of mammography in younger women have two basic causes, Kerlikowske said. First, women younger than 50 have dense breasts in which glandular tissue can obscure tiny tumors in X-ray pictures. In older women, the breasts become more fatty and tumors are easier to see.
Second, for reasons that scientists do not understand, breast cancer tends to be a more aggressive disease in younger women than in those 50 and older, she said. When mammograms reveal tiny tumors in young women, the tumors are far more likely to have spread than are similar tumors in older women. In such cases, there is no significant benefit to early detection, she added.