The study was published online Aug. 5 in Radiology
In the new study, Malmgren and her colleagues looked at data from a registry of women with breast cancer. They found more than 1,100 women over age 75 diagnosed with early- to late-stage breast cancer from 1990 to 2011.
The registry had information on how the cancer was diagnosed, the stage and other data. The detection of cancers with mammography increased over time during the study, from 49 percent to 70 percent.
Most mammography-detected cancers were in the early stage, while those found by doctors and patients were more likely to be advanced.
Those detected by mammography were more likely to need less aggressive treatments as well.
The study said that breast cancer survival was better in women whose cancer was detected by mammography, with 97 percent alive five years later. In comparison, 87 percent of those with invasive cancers found by their doctor or themselves were alive at the five-year mark.
However, the study was only able to show a link between mammography and improved survival. It wasn't able to prove that mammography was directly linked to the increased survival.
In addition, Liefers argued that the conclusion that fewer women died of breast cancer if it was detected by mammography may not be accurate. Other factors may play in to the survival besides the screening itself, he said. For instance, patient-detected tumors may be more aggressive than mammography-detected tumors.
Findings that do favor screening for older women include the decrease in advanced cancers and the increase in early cancer detection, Liefers said.
The take-home message, according to Malmgren, is for women 75 and over to get a mammogram every other year. That advice only holds true if women have a life expectancy of five years
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