Breast cancer before 50 linked to increased risk of colorectal cancer

Last Updated: 2017-05-08

By Will Boggs MD

NEW YORK (Reuters Health) - Women who develop breast cancer before age 50 have an increased risk of colorectal cancer and should be screened at intervals different from the general population, according to the authors of a systematic review and meta-analysis of studies involving more than one million women.

Earlier studies of the association between breast cancer and colorectal cancer have yielded inconsistent results, with some reporting higher risks of colorectal cancer in breast cancer survivors and recommending earlier or more frequent colorectal cancer screening and others finding no increased risk.

To investigate the issue, Dr. Lauren D. Gerson from California Pacific Medical Center and University of California, San Francisco and colleagues used data from 37 retrospective cohort studies and eight case-control studies including 1.06 million women with breast cancer, 9,097 of whom developed colorectal cancer.

In four studies that stratified women with breast cancer by age above or below 50 at diagnosis, those diagnosed with breast cancer before age 50 were 2.5 times as likely as those diagnosed over age 50 to develop colorectal cancer.

Similarly, in three studies that divided women according to age above or below 45 at breast cancer diagnosis, women diagnosed before age 45 were also 2.5 times as likely as those diagnosed over age 45 to develop colorectal cancer, according to the April 20th Gastrointestinal Endoscopy online report.

In the eight case-control studies, there was a nonsignificant 12% increased risk of colorectal cancer in women with vs without breast cancer.

There was insufficient information to determine the risk of colorectal cancer in the subset of women with BRCA mutations.

“According to the SEER Cancer Statistics Review (1975-2012), 1.33% of 50-year-old women in the United States will develop colorectal cancer (CRC) by the time they are 70 years old,” the researchers note. “Our overall CRC event rate of 0.7% is lower than what would be expected for the general population and does not justify a recommendation for earlier CRC screening.”

“There is evidence from a smaller number of studies, to suggest that women who develop breast cancer at a younger age have a higher risk of developing CRC,” they add. “One may infer from this that women with breast cancer diagnosis at age less than 45 should start CRC screening earlier than 50 years of age; however, we currently do not have enough data to recommend what age. However, we feel that our data support an initial screening at age 45 for breast cancer patients at age less than 50 years.”

Dr. Fulvio Ricceri from University of Turin, Italy, who previously reported a 71% increased risk of colorectal cancer among women with breast cancer, told Reuters Health by email, "I have observed several limitations of the study. I do not understand why the authors performed a meta-analysis on prevalence of CRC and not on the standardized incidence ratio between subjects with breast cancer and subjects without breast cancer.”

“In fact, what is missing to support the authors' strong sentence ‘Our meta-analysis did not support early CRC screening for breast cancer patients’ is a comparison in CRC rates between subjects with or without breast cancer,” he said.

Dr. Gerson did not respond to a request for comments.

SOURCE: http://bit.ly/2qhFu3u

Gastrointest Endosc 2017.