Women under 50 gain little breast cancer survival benefit from mammography, according to a new analysis of screening trials. Some experts still insist testing of younger women saves lives.
The study, published today in the Journal of the National Cancer Institute, concluded that most of the reduction in breast cancer deaths among women who started mammography screening between ages 40 and 49 came as a result of testing done after they were 50.
This finding supports the National Cancer Institute position that breast cancer mammography before age 50 is of reduced value and that it should not be recommended except in individual cases.
The American Cancer Society, however, continues to recommend regular mammographic exams for women beginning at age 40.
In the new study, a team led by Harry J. de Koning of Erasmus University in Rotterdam, The Netherlands, used a new computer modeling technique to evaluate five Swedish studies that tested the value of mammographic screening for women in different age groups.
The new analysis found that among women age 50 through 69, mammograms reduced breast cancer mortality by 29.5 percent.
For women who started mammography screening between ages 40 and 49, the study found a reduction in mortality of 3 percent. The study said previous findings of a 10 percent reduction in breast cancer deaths among this age group may have been skewed by the fact that many of the breast cancers were detected in these women only after they turned 50.
This means their cancers would have been found by the later-age screening and that they achieved no benefit from starting the screening at an earlier age.
The researchers estimated that 70 percent of the mortality reduction reported in the earlier studies may actually have resulted from screenings after age 50.
But the study does not settle the issue of when women should start regular mammography.
In an editorial in the Journal, Robert A. Smith of the American Cancer Society said there are still studies that show a distinct survival benefit for regular mammography tests for women 40 through 49.
“While we do not have the same quality of evidence about the efficacy of mammography in women aged 40 to 49 years compared to women aged 50 years and older, there are compelling data that mammography is beneficial to the 40-to-49 age group,” said Smith.
However, a counter-editorial by Drs. A. Patrick Forrest and Freda E. Alexander said studies in the United States, Sweden, Scotland and Canada all support the idea of not promoting regular mammography for all women in their 40s.
A final answer to the controversy may come from long-term studies comparing the benefits of mammography screening at different ages and taking into account the age at which cancers are first detected. Results of these studies are not expected until about 2003.