Mammogram reveals increased density (arrow) of the right breast. Image source: Indian J Radiol Imaging 2010 May;20(2):98–104.

Excluding women aged 40 to 49 from annual screening mammography exams under the revised U.S. Preventative Service Task Force (USPSTF) mammography guidelines would have a negative effect on survival, according to research presented last week at the American Society of Breast Surgeons annual meeting in Washington, DC.

A 10-year retrospective study conducted at the University of Missouri in Columbia found that mammography detected smaller tumors with less nodal metastasis than were identified through clinical breast exams among women in this age group.

“Breast cancer has a better prognosis when treated before tumors become palpable and identifiable through a physician or self-breast exam,” said researcher Paul Dale, MD, chief of surgical oncology at Ellis Fischel Cancer Center at the University of Missouri School of Medicine. “The study also found that tumors identified through mammography generally had better outcomes after treatment than those found through clinical exams.”

Dale and his colleagues examined the records of 1,581 women treated for breast cancer at the tertiary referral center between 1998 and 2008. Of the patients, 20 percent were between the ages of 40 and 49. Forty-seven percent of these patients were diagnosed through mammography and 53 percent through clinical exams or other non-mammographic methods. In the mammography group, the mean tumor size was 20 mm in diameter, while non-mammographically identified tumors were 30 mm, a highly significant difference in size, noted Dale. The study also found that the frequency of lymph node involvement in the clinically detected groups was about twice that of mammographically detected patients.

The researchers estimated the five-year disease-free survival rate at 94 percent for the group receiving mammograms and 78 percent for those who did not receive the screening exams. Node negativity and tumor size were significantly associated with an increase in survival.

“This study found that 20 percent of women diagnosed with breast cancer in our institution are under age 50, and almost half of their tumors were detected through mammography. Given recent advances in targeted treatment of early stage cancer, under these new guidelines, younger breast cancer patients not undergoing screening and early detection may miss out on important therapy that could significantly impact their survival,” Dale emphasized.

Dale stressed the role of full-field digital mammography in younger women with dense breast tissue, noting that many of the studies USPSTF used in its decision-making process predated digital mammography. “One concern underlying the new recommendations is that mammography in younger women is less effective and results in too many biopsies that are unnecessary and potentially traumatic for patients. Perhaps today’s advancing imaging technologies, as well as less invasive biopsies, will help to eliminate those concerns.”
 
“Despite significant objections to these new guidelines, few researchers have specifically looked at mammography and its long-term impact on outcomes in younger women," he explained. "This study provides important new information.”