Dec. 14, 2004 -- Getting a mammogram every two years appears to be as effective as annual screening in women over 50. But the same may not be true for women in their 40s.
Women in their 40s need yearly exams to maximize their chances of catching breast cancers early, new research shows.
But an expert with the American Cancer Society says they will continue to recommend annual mammograms for all women over 40.
One of the main goals of mammograms is to catch breast cancer at an early stage, while it is more easily treatable.
Researchers from Seattle's Fred Hutchinson Cancer Research Center found that the diagnosis of advanced cancers among breast cancer patients over 50 was the same whether the women were screened annually or every two years.
Women in their 40s who had annual mammograms had fewer late-stage cancers than those screened every two years.
The findings add to the evidence that many women may not need annual mammograms, but the optimal interval between breast cancer screenings remains controversial. The American Cancer Society continues to recommend that all women aged 40 and older have annual mammograms. But the guidelines of the National Cancer Institute call for screening every one to two years.
American Cancer Society spokeswoman Debbie Saslow, PhD, tells WebMD that the new study bolsters the organization's view that yearly screening is especially important for younger women.
"We feel very strongly that women in their 40s should be screened every year," she says. "Younger women tend to have faster growing cancers so it makes sense that annual screening would be especially beneficial for them."
Any Harm in Waiting?
The newly published study included data from more than 4 million women. Researchers identified 2,400 breast cancer patients who had mammograms every two years prior to diagnosis and 5,400 who had annual screening mammograms.
Among women over 50 the researchers found no difference in the number of advanced breast cancers between women that received mammograms annually versus every other year. They also reported that annual screening did not appear to benefit women in this age group with denser breasts. Mammography screening tends to be less effective in women with dense breasts.
A total of 28% of the women in their 40s who got mammograms every two years were diagnosed with late-stage breast cancer, compared with 21% of women in the age group who got annual screenings. The findings are published in the Dec. 15 issue of the Journal of the National Cancer Institute.
"We saw no harm in women 50 and over being screened every two years instead of every year," researcher Emily White, PhD, tells WebMD.
No Change in Policy
White says the findings could be of benefit to policy makers who continually weigh the costs versus benefits of mammography screening. But Saslow says the American Cancer Society will continue to recommend annual screenings for all healthy women over 40.
"This research confirms some early studies and contradicts others," she says. "We do still feel that annual screening is the best policy, especially for younger women."
Saslow says she frequently gets telephone calls form public health officials who don't have the money to screen all eligible women every year.
"They ask us if they should screen fewer women more often or more women less often," she says. "What we usually tell them is that we would love to have everybody follow our guidelines. But if they can't, we recommend screening women every year before menopause and every 18 months after menopause. That seems to be a good compromise."