Managing Obesity in Patients With Cancer: New ASCO Guide

Roxanne Nelson

May 13, 2014

Obesity is a leading cause of cancer and a factor that complicates patient care following a cancer diagnosis, says the American Society of Clinical Oncology (ASCO) in a new guide about obesity and cancer aimed at healthcare professionals. More than one third of US adults and 17% of US children and adolescents are categorized as obese, the society notes. The rates of obesity are even higher in several subgroups. For example, 54% of non-Hispanic black women over the age of 20 are categorized as obese. Therefore, this issue is poised to become an increasingly critical consideration in the care of patients with cancer.

"Obesity and Cancer: A Guide for Oncology Providers" is now available and accessible on the society Web site.

A companion patient guide, "Managing Your Weight After a Cancer Diagnosis," along with other resources on weight management, are available on ASCO's patient Web site, Cancer.Net.

"Obesity is a defining public health challenge for our nation today," commented Clifford A. Hudis, MD, president of ASCO. "As oncologists, we have an obligation to take on this challenge, providing ways to reduce the risk of obesity-related cancers, and equipping physicians and patients with the education and tools they need to ensure everyone receives the best possible cancer care," he said in a statement.

Obesity is quickly overtaking tobacco as the leading preventable cause of cancer, ASCO notes in the guide. More than 40,000 cancer cases attributed to obesity are diagnosed every year, while being overweight and obese has been implicated in 15% to 20% of all cancer-related mortality.

In addition, obesity is associated with many practical challenges in detecting cancer, as well as affecting local and systemic treatment of the disease. As an example, ASCO points out, obesity can influence the accuracy of cancer diagnostics secondary to factors such as hemodilution of tumor biomarkers and lowering the quality of imaging. It can also pose problems for administration of radiation therapy and surgery, and may be associated with certain surgical complications. In addition, chemotherapy doses may need to be increased in obese patients with cancer; otherwise, they may received suboptimal doses, which can affect the chance of cure. ASCO released a guideline on this issue in 2012.

The new ASCO guides are geared toward helping oncologists work with their patients in order to achieve the best outcomes regardless of their weight. They include:

  • A review of the scientific evidence that has emerged on the link between obesity and poorer cancer outcomes;

  • Recommendations for clinicians to help patients locate resources and services to lose weight and increase their level of activity;

  • Tools designed to improve communication between physicians and patients;

  • Guidance on insurance coverage and reimbursement for care related to obesity, including behavioral counseling, rehabilitation services, and medical interventions;

  • Information on services that are now available through the Affordable Care Act for services related to obesity; and

  • Links to additional resources, including relevant clinical practice guidelines and available programs, that help cancer survivors maintain healthy lifestyles

"There are still many unanswered questions remaining in the realm of weight, diet and cancer risk, but we can't wait for them to be answered before we act," said Dr. Hudis. "We recognize that cancer cannot be addressed in isolation from obesity's other harmful effects, but we also need to aggressively build awareness — just as we did years ago with tobacco — that obesity is a major contributor to the nation's cancer burden."

Later this year, ASCO will issue a policy statement and convene a summit for researchers to help identify and prioritize future research efforts.

Obesity Linked to Poorer Outcomes

As previously reported by Medscape Medical News, a growing number of studies have demonstrated an association between obesity and increased risk of developing cancer, as well as poorer outcomes. One large retrospective analysis found that obesity is an independent prognostic factor for mortality and development of distant metastases after a diagnosis of breast cancer. After adjustment for disease characteristics, the risk of developing distant metastases after 10 years was significantly increased (by 46%) in patients with a body mass index (BMI) of 30 kg/m2. The risk of dying of breast cancer after 30 years was also significantly increased (by 38%).

Another study pointed to obesity as a risk factor for the increasing mortality of postmenopausal women after colon cancer diagnosis. The findings suggested that abdominal obesity is more predictive of mortality from colon cancer than is general obesity. Women with the highest waist-to-hip ratio (WHR), which reflects abdominal obesity, had a 30% to 40% greater risk of dying of colon cancer than women with the lowest WHR.

Data from a study published last year showed that patients with pancreatic cancer who were obese in the years before their diagnosis have reduced survival. Patients with pancreatic cancer who had a prediagnostic BMI in the obese range lived 2 to 3 months less than patients who had a healthy weight before their diagnosis.

The obesity and cancer provider guide is funded through the Conquer Cancer Foundation with support from Roche and Ethicon Endo-Surgery.

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