By Elizabeth Fernandez | UCSF.edu | February 5, 2013
Among older women, getting a mammogram every two years was just as beneficial as getting a mammogram annually, and led to significantly fewer false positive results, according to a study led by UC San Francisco.
The national study of more than 140,000 women between the ages of 66 and 89 appeared online on Feb. 5 in the Journal of the National Cancer Institute.
"Screening every other year, as opposed to every year, does not increase the probability of late-stage breast cancer in older women," said lead author Dejana Braithwaite, PhD, a UCSF assistant professor of epidemiology and biostatistics. "Moreover, the presence of other illnesses such as diabetes or heart disease made no difference in the ratio of benefit to harm."
From 1999 to 2006, data were collected on 2,993 older women with breast cancer and 137,949 women without breast cancer – "the largest available screening mammography data set in the United States," according to Braithwaite. The data were obtained from five Breast Cancer Surveillance Consortium (BCSC) mammography registries in Washington, California, North Carolina, New Hampshire and Vermont.
The researchers found no difference in rates of late-stage breast cancer between women screened annually and women screened biennially.
However, they found that 48 percent of women between the ages of 66 and 74 who were screened every year had false positive results, while 29 percent of women in the same age range who were screened every two years had false positives.