Obesity and cancer outcome : The Lancet

Obesity and cancer outcome : The Lancet

Obesity and cancer outcome

The Lancet

 

12 million Americans are cancer survivors and a staggering two-thirds of Americans are currently considered overweight or obese. On April 3, the National Cancer Policy Forum of the US Institute of Medicine released a welcome report entitled The Role of Obesity in Cancer Survival and Recurrence. Many epidemiological studies have identified obesity as a factor in cancer risk and prognosis. Obesity is associated with higher cancer incidence, recurrence, progression, and death. The report emphasises how little is still known about the precise cellular mechanisms that link obesity with cancer.

Adipose tissue can behave as an endocrine organ by generating hormones, growth factors, and cytokines that can disrupt regulation of cell growth and survival—the hallmark of malignancy. Knowing the precise cellular targets involved in this interplay could lead to targeted therapeutic approaches for controlling both cancer and obesity. For example, appropriate animal models could allow investigation of mechanisms of obesity and diabetes in precise genetic models of human cancers.

What is not yet known is whether weight management changes the prognosis and outcome in different cancers. The simple solution of tracking individuals' BMI and bodyweight during clinical trials to analyse effect on cancer outcomes needs to become standard practice. Another area of clinical controversy is related to proper chemotherapy dosing in obese cancer patients. Total body-surface area is used to calculate the chemotherapy dose, which does not take into account the body's composition (such as an individual's fat percentage). This approach often leads to suboptimum doses of chemotherapy.

But the most important lesson of this report comes from the basic science of obesity-associated cancer risk. Our population-level responses—which have largely failed—are based on a far too simplistic understanding of how obesity contributes to cancer. To address this challenge demands not more poorly thought out intervention trials. 

 Instead, we need greater understanding of the biological mechanisms underpinning cancer and obesity.