Breast Cancer Death Risk May Be Higher for Some Obese Women

Obesity increased death risk in premenopausal women with breast cancer fueled by estrogen

(RxWiki News) Shifting female hormones can affect wellness and disease alike. Breast cancer, a disease influenced by hormones, also may be affected by women’s body size.

A new preliminary analysis of dozens of clinical trials involving 80,000 females showed that being overweight raised the risk of dying from breast cancer-related causes for some of those who had not undergone menopause.

"Work with your doctor to establish a healthy weight loss plan."

Hongchao Pan, PhD, a researcher at the University of Oxford in Oxford, United Kingdom, was this study’s lead author.

For this preliminary study, which is scheduled to be presented at the American Society of Clinical Oncology's upcoming conference, Dr. Pan and his colleagues reviewed data from 70 clinical drug trials enrolling 80,000 women in the early stages of breast cancer. The women were receiving the same types of cancer treatments.

Of those 80,000 women, 60,000 had estrogen receptor-positive breast cancer, which means that estrogen caused their cancer cells to grow. Cancer treatment is determined, in part, based on which hormones are believed to play a role in the spread of a person's cancer.

These researchers analyzed the women's breast cancer outcomes for roughly eight years. Among the 20,000 premenopausal women who were estrogen-receptor positive, these researchers concluded that the risk of breast cancer-related death was 34 percent higher in those women who were obese than in pre-menopausal women were not obese.

That would, for example, raise the risks of dying from breast cancer within 10 years from 15 to 20 percent, these researchers concluded.

“Obesity substantially increases blood estrogen levels only in post-menopausal women, so we were surprised to find that obesity adversely impacted outcomes only in pre-menopausal women,” Dr. Pan said in a press announcement about the study. “This means we don’t understand the main biological mechanisms by which obesity affects prognosis.”

The women were determined to be obese based on medically accepted standards for healthy weight and overweight.

Being overweight had no affect on the 40,000 postmenopausal women whose cancer was estrogen-receptor positive or estrogen-receptor negative, which means that estrogen does not affect the cancer.

This preliminary study has not been accepted for publication in a scientific journal. It is slated to be presented during American Society of Clinical Oncology's (ASCO) annual meeting, May 30 through June 3 in Chicago.

"This study is part of the growing body of evidence showing that patients who are obese generally fare worse with cancer — in this case, younger women with breast cancer," Clifford A. Hudis, MD, FACP, ASCO president, said in a press announcement.

Dr. Hudis continued, “With some two-thirds of our nation’s adult population now obese or overweight, there’s simply no avoiding obesity as a complicating factor in cancer care. ASCO is working to support physicians and patients in addressing this challenge, and we urge researchers to examine new strategies for reducing obesity’s cancer-related toll."

Cancer Research UK, the Medical Research Council and the British Heart Foundation funded this study.

These researchers did not report whether they had financial investments or other involvements that would affect study design, outcome and analysis.

Review Date: 
May 24, 2014