Obesity in Breast Cancer Survivors Linked to Higher Risk of Developing Secondary Cancers

A new study shows that overweight breast cancer survivors have a statistically significant increased risk of developing second primary cancers, and obesity is strongly associated with an increased risk of various cancer types.

Overweight breast cancer survivors have a statistically significant increased risk of developing second primary cancers, according to a new study published in the Journal of the National Cancer Institute. Obesity is strongly associated with an increased risk of cancer, with 55% of all cancers in women occurring in those who are overweight or obese.

Studies have found women diagnosed with breast cancer have an 18% increase in risk for developing a second cancer when compared to the general population. This is likely due to shared risk factors between the first and second cancers, genetic susceptibility, and long-term effects of breast cancer treatment.

Women diagnosed with an invasive breast cancer were at a small but statistically significant increased risk for second cancers associated with increasing BMI. This association became more pronounced when the analysis was limited to second breast cancers or cancers considered obesity-related, and was strongest for a diagnosis of estrogen receptor-positive second breast cancer.

“These findings have important public health implications given the number of breast cancer survivors with excess body weight,” said Heather Spencer Feigelson, PhD, senior investigator at the Kaiser Permanente Colorado Institute for Health Research, in a prepared statement. “Our study examined whether cancer survivors are at an increased risk of developing a second cancer and what factors contribute to this increased risk. Our findings truly underscore the need for effective weight loss prevention strategies, including nutrition and physical activity guidelines, for breast cancer survivors.”

The study followed 6481 women from Kaiser Permanente in Colorado and Washington, of whom 822 developed a second cancer. Data show 33.4% were overweight at the time of their initial diagnosis, and 33.8% were obese. The mean age at initial breast cancer diagnosis was 61 years, and 82.2% of the cohort was white. The researchers evaluated a number of outcomes, including all second cancers, obesity-related second cancers, any second breast cancer, and ER-positive second breast cancers. Obesity related cancer includes colorectal, uterine, ovarian and pancreatic cancer.

"This study illustrates that modifying one's BMI may result in significant health and quality of life benefits among breast cancer survivors," explained Clara Bodelon, PhD, MS, in the statement.


Weight linked to risk of second cancer after breast cancer [news release]. EurekAlert; April 12, 2021. Accessed April 15, 2021. https://www.eurekalert.org/pub_releases/2021-04/kp-wlt040921.php