This suggests a role for continued mammography screening among women aged 75 years and older, according to data presented at the AACR Annual Meeting 2013, held in Washington, D.C., April 6-10.
"We found that for women age 75 and older, a longer time interval between the last mammogram and the date of breast cancer diagnosis was associated with a greater chance for dying from breast cancer," said Michael S. Simon, M.D., M.P.H., leader of the breast multidisciplinary team at Barbara Ann Karmanos Cancer Institute in Detroit, Mich., and professor of internal medicine and oncology at Wayne State University School of Medicine.
To evaluate whether time between mammograms affected breast cancer mortality, Simon and colleagues analyzed data from 8,663 women in the Women's Health Initiative observational study or clinical trial who had been diagnosed with breast cancer during a 12.2-year follow-up.
An interval of five or more years between a woman''s last mammogram and breast cancer diagnosis was associated with advanced-stage disease in 23 percent of women compared with 20 percent of women with an interval of six months to a year, a statistically significant difference, which may affect large numbers of women.
In an adjusted analysis, researchers found a longer interval between mammogram and diagnosis was associated with a significantly increased risk for breast cancer mortality among women aged 75 or older at diagnosis. Women aged 75 years or older at diagnosis who had an interval of five years or more between mammogram and diagnosis or who had never had a mammogram had a threefold greater risk for death from breast cancer compared with women who had an interval of six months to a year between mammogram and diagnosis. These relationships were not found among younger women.
"I am not sure why we are seeing these results particularly for older women. Tumors of younger women were more likely to be a little more unfavorable overall," Simon said. "It is possible that the differences in the relationship between screening interval and mortality in older versus younger women may be related to the more aggressive nature of the tumors in younger women, which might obliterate the effects of more screening. Other reasons may include differences in cancer treatment, information that was not available for this cohort of women."
According to Simon, physicians should discuss the risks and benefits of mammography with older patients and encourage them to continue mammography screening. "Our findings suggest that regular mammography should be continued for older women every one or two years; however, as with younger women, mammography screening should be considered in light of the overall health of the individual woman," he said.