Research Finds BMI May Not Be the Best Obesity Indicator to Assess Risk for Lung Cancer

New research suggests the process currently used to calculate how obesity is measured may affect its consideration as a risk factor for lung cancer, according to a study published in the Journal of Thoracic Oncology.

Although the association between obesity evaluation and both cancer incidence and outcome are apparent in some solid tumor types, such as breast, esophageal, and colon cancer, the link between obesity and lung cancer carries subtle differences from the other cancer types, according to the study authors.

The researchers analyzed patients with lung cancer before they underwent surgery and calculated their excess body weight using visceral fat index measured by CT scans.

“While BMI is easy to measure, its use has been criticized due to its inability to discriminate between fat and lean body mass,” said lead researcher Sai Yendamuri, MD, in a press release. “BMI also fails to account for body fat distribution. It is becoming increasingly recognized that 'visceral' or 'central obesity' is the primary driver behind the health outcomes linked to high body fat.”

The researchers noted that prior research shows a close correlation between visceral obesity as determined by analysis of a single slice of abdominal CT and a volumetric analysis of visceral fat. The authors of the current study said this shows the potential for of using image-based measurements in a large cohort of patients.

“Based on the established knowledge described above, we sought to measure central obesity in a cohort of [patients with] stage I [non-small cell lung cancer (NSCLC)] [who were] undergoing lobectomy at our institution and examine its association with oncologic outcomes,” said Joseph Barbi, PhD, first study author, said in the press release.

Barbi and his colleagues examined 554 patients with stage 1 and 2 NSCLC undergoing lobectomy. Reliable fat area measurements were acquired from 513 patients: 499 at L3, 5 at L2, and 9 at L1. Similarly, 159 patients with advanced-stage NSCLC with molecular testing had reliable fat area measurements: 146 at L3, 10 at L2, and 3 at L1.

Correlation of measurements between L2 and L3 levels and between L1 and L3 levels were good, which meant that in the few cases in which measurements at L3 were not available, measurements at L2 or L1 were used. CT scans of these patients could be used to clearly identify individuals with distinctly predominant visceral or subcutaneous adipose tissue distributions.

“These findings clarify the truly negative relationship that exists between central obesity and lung cancer outcomes, and they present a viable alternative to the use of BMI in retrospective studies of obesity rooted in biology with clear relevance to cancer outcomes,” Barbi said in the press release.

The clinical and preclinical findings indicate a common potential mechanism for the increasing impact of obesity on the development of tumor burden among obese patients, specifically an apparently multifaceted immune dysfunction found in the tumors of obese mice and patients, according to the study authors.

“Our study provides much needed clarity to the relationship between adiposity and NSCLC patient survival, providing firm scientific justification for the targeting of obesity’s pro-tumor effects, which include decidedly adverse effects on the antitumor immune response,” Yendamuri said in the press release. “Our findings also reaffirm the utility and relevance of available mouse models to study further the mechanisms of obesity’s lung cancer promoting effects. Importantly, they also validate a refined approached for studying obesity in retrospective data sets [of patients with cancer].”

REFERENCE

Research suggests BMI may not be best obesity indicator to assess risk for lung cancer. IASLC. Published May 27, 2021. Accessed June 3, 2021. https://www.iaslc.org/iaslc-news/press-release/research-suggests-bmi-may-not-be-best-obesity-indicator-assess-risk-lung