Research project examines link between obesity, cancer

The National Cancer Institute has launched the Transdisciplinary Research on Energetics and Cancer initiative, a major effort to investigate exactly how obesity increases the risk of cancer and determine what interventions will reduce its impact.

"NCI is determined to help avoid an increase in cancer deaths in the 21st century due to obesity like the one caused by tobacco in the 20th century," said Robert Croyle, PhD, director of the institute's Division of Cancer Control and Population Sciences.

The association between obesity and cancer is long established. Most recently, a study published in the Oct. 1 issue of Clinical Cancer Research found that obese men successfully treated for prostate cancer were more likely to have their cancer recur than those who did not carry excess weight. That risk was higher if the men had a history of rapid weight gain.

But exactly how this link works and what can be done about it is a mystery. Thus, NCI will provide $54 million in funding to four centers over the next five years to uncover answers.

"We're looking at why there might be a relationship, what the mechanism might be and [how to] determine what people have to do to reduce their risk," said Anne McTiernan, MD, PhD, one of the principal investigators and director of the Prevention Center at the Fred Hutchinson Cancer Research Center in Seattle. The center is also coordinating the projects.

Researchers will investigate the impact of excess sugar on cell growth and hunt for molecular markers that can measure a person's weight-associated risk of cancer. The goal is that this eventually will enable physicians to test for it to determine what a patient's risk is and track how it changes over time.

"What are the markers that we should be looking at to know that the weight loss is going to be effective in preventing obesity-related cancer?" said Nathan A. Berger, MD, one of the principal investigators and the Hanna-Payne Professor of Experimental Medicine at Case Western Reserve University in Cleveland.

Another objective of the project is to delineate more precise interventions related to weight and cancer prevention. Also blurry is what behavior is most important for a patient to change. Researchers hope that the initiative will arm physicians with facts to better pinpoint steps patients must take to reduce their chance of developing cancer.

"We can take mice and feed them a Western diet, and some mice will get obese," Dr. Berger said. "But is it the obesity or the diet that is related to cancer? Do patients need to lose weight or change their diet or both?"

Cancer prevention experts praised the initiative for having the potential to make counseling about weight issues more tailored and more relevant to an individual patient. It also could lead to new cancer prevention tools.

"This could be a very fruitful line of research," said Richard C. Wender, MD, American Cancer Society first vice president and chair of the Dept. of Family Medicine at Jefferson Medical College of Thomas Jefferson University in Philadelphia. "We have to give general blanket statements that being obese is bad and bad in all ways, but it's not that simple. Fit obese people can have similar risks to unfit thin people."

Those involved in this initiative also suggested that a better understanding of the link between obesity and cancer might provide more motivation to patients to lose weight. This motivation could be greater than what is provided by other conditions, such as heart disease, that in many people's minds are more closely associated with excess weight.

"Patients don't worry so much about heart disease," Dr. McTiernan said. "But a lot of people are driven by a fear of cancer."