ESMO 2017-CENTRAL OBESITY AND RISK OF CANCER

More than overweight alone, central obesity — defined as  high ratio of trunk fat to peripheral fat — places postmenopausal women at a higher risk for cancer diagnosis, according to a study presented here at the European Society for Medical Oncology (ESMO) 2017 Congress.

"The findings put a new spin on weight management priorities for women in this age group, who are prone to abdominal weight gain," said study investigator Line Maersk Staunstrup, MSc, a PhD student with Nordic Bioscience and ProScion in Herlev, Denmark.

In assessing cancer risk, body mass index (BMI) and fat percentage may not be adequate measures because they fail to assess the distribution of fat mass, she explained. "Fat is not just fat, but where in your body it is stored is significant," she added.

"Our study shows that avoiding central obesity may confer the best protection," Staunstrup said.

The Danish Study and Results

The Prospective Epidemiologic Risk Factor study was an observational, prospective cohort study designed to improve understanding of age-related diseases in Danish postmenopausal women.

From 1999 to 2001, 5855 women (mean age, 71 years) were enrolled. Investigators accessed medical and demographic background information. Dual-energy x-ray absorptiometry (DXA) was performed at time of enrollment. DXA scans are the most accurate way to measure bone mass, bone-free lean mass, and fat mass, the authors note.

Data were subgrouped into three different categories: breast/ovarian cancer, lung/gastrointestinal cancer, and other cancers. Cox proportional hazard regression models were used to examine the association between body fat distribution and the risk for cancer incidence, adjusted for standard risk factors, including BMI.

Cancer diagnoses and information on death causes were obtained from different Danish registries up to 2012. Mean follow-up was 12 years.

Using information from national cancer registries, the study investigators reported 811 solid cancers in the women and showed that central obesity was a significant independent predictor of cancer diagnosis up to 12 years after baseline (hazard ratio [HR], 1.30; 95% confidence interval [CI], 1.11 to 1.52; P < .001). Surprisingly, Staunstrup noted, neither BMI nor fat percentage posed a significant risk for cancer diagnoses.

Specifically, there were 293 breast and ovarian cancers, 345 lung and gastrointestinal cancers, and 173 other cancers. Among these cancer groups, central obesity was a risk for only lung and gastrointestinal cancer diagnoses (HR, 1.42; P < .01).

Staunstrup was also surprised that central obesity was not an independent risk factor for breast and ovarian cancer diagnoses.

Looking in detail at specific cancers and risk factors, the investigators determined that only lung and gastrointestinal cancers were associated with central obesity (for lung cancer: HR, 1.68 [95% CI, 1.12 - 2.53; P < .05]; for gastrointestinal cancer: HR, 1.34 [95% CI, 1 to 1.8; P < .05]).

Additional cancer risk factors were older age, receipt of hormone replacement therapy, and smoking, but after adjustment for these risk factors, fat ratio remained an independent risk factor, the study authors reported.

The average elderly women can very much use this information, as it is known that the menopause transition initiates a shift in body fat towards the central trunk area. Therefore, elderly women should be especially aware of their lifestyle when they approach the premenopause age," Staunstrup said.

"Clinicians can additionally use the information for a preventive conversation with women who are in higher risk of cancer. While clinicians have access to whole-body DXA scanners at most hospitals, portable DXA scanners have become available on the commercial market, and this may allow regional bone and fat scanning. However, it may not be the most reliable for measuring central obesity," she concluded.

Commenting on the study, Andrea De Censi, MD, from Galliera Hospital, in Genova, Italy, said the study provides important confirmation of the role of obesity and particularly insulin resistance in the etiology of several cancers.

"While obesity has previously been linked to cancer risk, the link to lung cancer is new and intriguing," he said in a statement.

"Increases in insulin, resulting from overconsumption of simple carbohydrates, such as potatoes, wheat, rice, and corn, result in fat accumulation that is specifically visceral and abdominal," Dr De Censi explained. Insulin also has detrimental effects on hormone production, and adipose cells in fat tissue increase chronic inflammation throughout the body, another risk factor for several cancers.

"These data open the door for clinicians to initiate a number of interventions in obese patients. In addition to fat loss with diet and exercise, there may be a potential role for a diabetes drug, such as metformin, which can lower insulin effects and contribute to cancer prevention," Dr De Censi said.