By Brian Casey, staff writer

February 12, 2018 -- Having a first-degree relative with a family history of breast cancer sharply increases the risk of breast cancer in women older than 65, according to a study of more than 400,000 women published February 12 in JAMA Internal Medicine. The findings could weigh into the debate over whether these women should undergo mammography screening.

Women ages 65 to 74 with a first-degree relative who once had breast cancer had a 48% higher breast cancer risk themselves; for women 75 and older, the elevated risk was 44%. The women's breast density status had no statistically significant effect on their risk of cancer, according to the research team led by Dejana Braithwaite, PhD, of Georgetown University (JAMA Intern Med, February 12, 2018).

"Family history of breast cancer does not decline as a breast cancer risk factor as a woman ages," Braithwaite said in a statement. "The relationship didn't vary based on whether a first-degree relative's diagnosis was made in a woman age 50 or younger, or older than age 50."

Breast screening guidelines

Currently, the U.S. Preventive Services Task Force (USPSTF) recommends breast screening every two years for women ages 50 to 74 who are at average risk for breast cancer. But the USPSTF does not recommend screening for older women, stating that the evidence is inconclusive to assess the risks and benefits of the test.

Dejana Braithwaite, PhD,
Dejana Braithwaite, PhD, from Georgetown University.

At the same time, many public health experts are recommending that screening guidelines be shifted from a basis on age to one centered on cancer risk. To that end, it's important to understand how factors such as having a family history of cancer could affect whether and how often a woman should be screened, Braithwaite and colleagues noted.

The researchers from multiple U.S. institutions examined records from seven registries in the Breast Cancer Surveillance Consortium from 1996 to 2012. In all, they analyzed the records of 403,268 women ages 65 and older who received a total of 472,220 mammograms, with 40% of the women being at least 75 years old. All of the women who were included supplied information via questionnaires on their family history of cancer in first-degree relatives.

At a mean follow-up time of 6.3 years, the subjects had experienced 10,929 invasive breast cancers. Women in both of the two age groups examined had an elevated cancer risk if they had a first-degree relative with breast cancer. Breast tissue density did not have a statistically significant effect on risk, however.

Effect of family history of breast cancer on cancer risk for women 65 and older
Age Hazard ratio for breast cancer in women with family history of breast cancer
All women Dense breast tissue Fatty breast tissue
65-74 years 1.48 1.32* 1.67*
≥ 75 years 1.44 1.55* 1.08*
* The difference in hazard ratio between dense and fatty breast tissue was not statistically significant.

"We found that first-degree family history remains an important risk factor for breast cancer even among women ≥ 75 and breast density does not significantly modify the association except perhaps in women with fatty breasts," Braithwaite and colleagues wrote.

The researchers also found that the age of the relative at the time of cancer diagnosis did not affect a woman's cancer risk.

Consistent with previous research

The results are consistent with previous research, the authors noted, such as a 2004 study by Sweeney et al that found that women ages 75 and older had a hazard ratio for cancer of 1.54 if they had a first-degree relative with cancer. On the other hand, the risk level reported in the new study was lower than in several other studies; however, the other studies included younger women, as well as women who were screened outside the U.S.

Braithwaite previously led a literature review that found evidence to support the benefits of mammography screening for women ages 65 and older. Indeed, in the current paper, the authors wrote that advancing age is a major risk factor for breast cancer, with risk peaking between the ages of 75 and 79. Braithwaite and colleagues found that the cohort of women ages 75 and older had the highest prevalence of family history of cancer in their study.

They advised that older women continue to consider mammography screening as they reach the upper limits of the USPSTF guidelines.

"Providers should continue to ask older women about family history of breast cancer to personalize mammography screening strategies," they concluded. "Crucially, family history needs to be taken into account when considering the potential benefits versus harms of continued mammography in this population."

Copyright © 2018

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