Obesity Raises Odds for Breast Cancer’s Return

By Cara Murez
HealthDay reporter

MONDAY April 19, 2021 (HealthDay News) – Most people know that obesity can lead to diabetes or heart disease, but being overweight can also play a role in cancer, researchers say.

A new study has found that breast cancer survivors who are overweight have a statistically significant increased risk of developing a second primary cancer – a cancer unrelated to their previous cancer.

The risk is likely due to risk factors shared between the two cancers – including obesity – as well as genetic susceptibility and long-term effects of breast cancer treatment, the study authors said.

“The risk is comparable to what we would see for initial breast cancer,” said Heather Spencer Feigelson, senior researcher at the Kaiser Permanente Colorado Institute for Health Research, in Aurora. “This is just another piece of evidence showing us how [excess weight] is really important. “

For the study, researchers looked at data from nearly 6,500 women treated at Kaiser Permanente in Colorado and Washington state. Roughly equal percentages were normal weight, overweight and obesity.


The study found that women who had invasive breast cancer had a low, but significantly higher risk of a second cancer as their body mass index (BMI) increased. (BMI is an estimate of body fat based on height and weight.)

This link was more pronounced when the analysis focused on cancers linked to obesity or second breast cancers, the researchers said. The link was strongest for a second estrogen receptor positive breast cancer diagnosis.

Of the 14 cancers listed by the International Cancer Research Center as being linked to obesity, some are common and some are more difficult to treat, Feigelson said.

Investigators found that 822 (nearly 13%) of the women developed a second cancer after an average follow-up of just over seven years. Of these, almost 62% were obesity-related cancer and 40% were a second breast cancer.

The 508 obesity-related cancers included 283 postmenopausal breast cancers; 70 colon / rectal cancers; 68 uterine cancers; 21 ovarian cancers; 23 pancreatic cancers; and 14 kidney cancers. There were less than 10 cases each of thyroid, esophageal, gallbladder, multiple myeloma, meningioma, liver and upper stomach cancers.


While being overweight appears to increase risk, the evidence that losing and keeping weight lowers risk is limited because losing weight is difficult, Feigelson said.

“Science suggests that, yes, if you are losing weight you should lower your risk, but really the best studies … are studies of women who have become bariatric. [weight-loss] surgery, and those who lose such an amount of weight have a lower risk of cancer, ”Feigelson said.

About 55% of all cancers in women occur in overweight or obese people.

Feigelson noted that there are many risk factors for breast cancer that women cannot do much about.

“For example, for these second breast cancers or second cancers after breast cancer, a risk factor is the treatment, and obviously you’re not going to give up on the treatment,” she said. “But it’s something that women can really have control over. And I think if you’re worried about cancer or if you’re a cancer survivor, having these things that you can control and do something about can be very important to you.


Incorporating healthy habits into your daily life can help prevent cancer. Maintain a healthy body weight, be active, and don’t sit too much, Feigelson advised.

The results were recently published in the Journal of the National Cancer Institute.

The researchers noted that one of the limitations of the study was the lack of diversity, as around 82% of the participants were white women.

Dr. Jennifer Ligibel, director of the Zakim Center for Integrative Therapies and Healthy Living at the Dana-Farber Cancer Institute in Boston, reviewed the results.

“I think this article really provides a compelling rationale for why it’s important to think about losing weight after being diagnosed with breast cancer,” she said.

Being overweight has a multifaceted effect on a person’s body, increasing levels of insulin and other metabolic markers, as well as inflammation, Ligibel said. It probably also depresses the immune system, she added.

Additionally, she noted that being overweight increases the levels of sex hormones which can also lead to the development of certain types of cancer.


“It’s probably not one thing, but the complex interplay between these different systems,” said Ligibel, who is part of another study investigating whether a weight loss program as part of the treatment of breast cancer can lead to lower rates of new cancers.

For many years, she noted, the American Cancer Society has made recommendations on nutrition, physical activity, and weight for cancer prevention and for cancer survivors. These include trying to achieve and maintain a healthy weight.

“Unfortunately, [a lot of people have] has gained weight as a result of the quarantine and everything else over the last year, but I think it’s a goal that we really need to think about at a societal level, ”Ligibel said.

More information

The United States Centers for Disease Control and Prevention has more on the causes and consequences of obesity in adults.

SOURCES: Heather Spencer Feigelson, PhD, cancer epidemiologist and principal investigator, Kaiser Permanente Institute for Health Research, Aurora, Colorado; Jennifer Ligibel, MD, associate professor, medicine, Harvard Medical School, and director, Leonard P. Zakim Center for Integrative Therapies and Healthy Living, Dana-Farber Cancer Institute, Boston; Journal of the National Cancer Institute, April 5, 2021

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