Oncologists often advise patients about the importance of exercise and a healthful diet. Now, due to the increased cancer burden associated with obesity, oncologists are being enlisted to play an even greater role in discussing weight management and improving dietary quality. The American Society of Clinical Oncology (ASCO) has started an “obesity initiative” to encourage oncologists to inform their patients that losing excess weight may help prevent disease recurrence following initial treatment.
For the first time, ASCO is recommending that oncologists take a lead role in referring obese patients to the appropriate sources where patients and their families can be helped by weight management professionals. Obesity is associated with negative outcomes among premenopausal and perimenopausal women with estrogen receptor-positive breast cancer, and obesity is also associated with a greater risk of prostate cancer recurrence and death. Overall, studies suggest that obesity may be overtaking tobacco as the leading preventable cause of cancer.
“It is a really important problem when you look at the number of obese individuals in the United States and what has been occurring over the last 10 years. We need to point it out to patients and we need to give them solutions,” said Kala Visvanathan, MBBS, a professor of oncology and epidemiology at Johns Hopkins Medical Center in Baltimore, MD. “It is a challenging problem for many patients to decrease weight, improve diet, and increase exercise. [Oncologists] have to help [patients] figure out how to go about it. It is not enough to just say lose weight and increase activity. You have to ask questions and give [patients] resources that point them in the right direction.”
Obesity rates have skyrocketed in the last 30 years and are now contributing to increased rates of diabetes, heart disease, and cancer. Researchers are finding that obese individuals may be at a significantly increased risk of not only developing cancer but also dying from it compared with nonobese individuals.1
Helping obese patients lose weight by the best possible means may be especially important following a cancer diagnosis. It is theorized that metabolic changes following weight loss may significantly improve outcomes. A recent review article looking at obesity and cancer rates found that bariatric surgery could reduce cancer risk among obese individuals.2 Daniela Casagrande, PhD, of the Universidade Federal do Rio Grande do Sul in Brazil and colleagues contrasted and combined results from 13 controlled and uncontrolled studies, which included information on 54,257 patients. They found that cancer occurred in only 1.06 cases per 1,000 person-years up to 23 years post-bariatric surgery. This was a markedly lower rate for the global population of obese individuals (2.12 cases per 1,000 person-years).
Obese patients often have increased levels of insulin and insulin-like growth factor and it is theorized that these metabolic factors may promote the development of tumors. “My group has demonstrated that obesity is associated with a higher risk of recurrence and poorer outcomes,” said ASCO immediate past-president Clifford A. Hudis, MD, FACP, of Memorial Sloan-Kettering Cancer Center and professor of medicine at the Weill Medical College of Cornell University in New York, NY. “It may be due to a low-grade chronic inflammation and we know that the inflammation can be modified.”
Dr. Hudis identified prostate cancer as a cancer that has a clear association with obese patients being diagnosed with a higher grade and a higher Gleason score compared with nonobese patients. Obese patients with prostate cancer also have worse outcomes compared with nonobese patients.
Wendy Demark-Wahnefried, PhD, RD, a nutrition scientist at the University of Alabama at Birmingham (UAB) has found that patients with prostate cancer who follow a low-fat diet and lose weight prior to prostatectomy have lower levels of vascular endothelial growth factor in their tumor tissue.3 Her team currently is conducting two follow-up trials to explore the effect of a strict weight-loss regimen in both men with prostate cancer as well as women with ductal carcinoma in situ. All the patients in both trials are scheduled for surgery to see if proliferation rates and other salient biomarkers are favorably influenced by weight loss.