Women with a family history of cancer other than breast cancer, especially ovarian cancer, were found to be at increased risk for breast cancer, according to the results of a cohort study recently published in Cancer.
Using the Swedish family cancer data sets, which is considered the largest data set for evaluating familial cancers, study researchers identified 5,099,172 Swedish women born after 1931 with at least 1 known first-degree relative.
Women with a first-degree relative who had 1 of the following 15 cancer types were found to have an increased risk of breast cancer: stomach, colon and rectum, liver, pancreas, respiratory system, ovary, cervix, prostate, kidney, bladder, skin, thyroid and other endocrine glands, lymphocytes, and cancer of unknown primary.
Women with a first-degree relative who had ovarian cancer were found to have the greatest risk of developing breast cancer (standardized incidence ratio [SIR]=1.25; 95% CI, 1.16-1.34), particularly when the relative was diagnosed with ovarian cancer before the age of 50 (SIR=1.4; 95% CI, 1.20-1.57).
“Despite the increased relative risks of breast cancer for women with various discordant cancers, only women with a family history of ovarian cancer reached screening level risk thresholds at considerably earlier ages,” the researchers wrote.
The 10-year cumulative risk of breast cancer was 2.2% when women were advised to start breast cancer screenings at age 50, but for women with a first-degree relative who had ovarian cancer, this risk threshold was reached 4 years sooner, at age 46.
“Our study demonstrated that women with a family history of ovarian cancer could be recommended to start screening at an earlier age,” investigators wrote.
Mukama T, Kharazmi E, Sundquist K, Sundquist J, Fallah M. Risk-adapted starting age of breast cancer screening in women with a family history of ovarian or other cancers: A nationwide cohort study. Cancer. Published online February 23, 2021. doi:10.1002/cncr.33456