Cancer Risk might not be predicted by Body Mass Index (BMI)

Body Mass Index (BMI) might not be a best obesity indicator to assess risk for lung cancer as per a study at the Rosewell Comprehensive Cancer Cancer in Buffalo, N.Y., published in the Journal of Thoracic Oncology (JTO), an official journal of the International Association for the Study of Lung Cancer. It is known that obesity is associated with the increased incidence of some solid tumor types such as breast, esophageal, and colon cancer. But the relationship between obesity and lung cancer is more nuanced, probably due to the use of traditional methods of measuring obesity, including the body mass index.

It is increasingly recognized that 'visceral' or 'central obesity' is the primary driver to high body fat and its outcomes. Although the BMI is easy to measure, its critics lie in its inability to discriminate between fat and lean body mass and also account for body fat distribution.

"Based on the established knowledge described above, we sought to measure central obesity in a cohort of [patients with] stage I NSCLC [who were] undergoing lobectomy at our institution and examine its association with oncologic outcomes," says Joseph Barbi, Ph.D., first author of the manuscript.

The study team thereby examined 554 patients with stage I and II NSCLC – lung cancer before they underwent lobectomy surgery and calculated their excess body weight using visceral fat index measured by CT scans.

Because patients with early-stage disease are typically treated with surgery alone, without other treatments that may complicate the analysis, the researchers believed they provide a context where the relationship between central obesity and tumor progression can be studied without additional therapy-associated confounders.

Visceral Fat and Lung Cancer Outcomes

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So the reliable fat area measurements were obtained in 513 patients: 499 (97.3 %) at L3, 5 (0.9%) at L2, and 9 (1.8%) at L1. Similarly, 159 patients with advanced-stage NSCLC with molecular testing had reliable fat area measurements: 146 (91.8%) at L3, 10 at L2 (6.3%) and 3 at L1(1.9%).

Interobserver correlation of VFI measurements was good. The correlation of measurements between L2 and L3 and between L1 and L3 levels was also good. Therefore, in the few cases where measurements at L3 were not available, measurements at L2 or L1 were used.

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The study thereby demonstrates negative relationship that exists between central obesity and lung cancer outcomes. Thus, the CT scans of these patients could be used to identify individuals with distinctly predominant visceral or subcutaneous adipose tissue distributions with clear relevance to cancer outcomes.

The team also report that an apparently multifaceted immune dysfunction prevalent in the tumors of obese mice and patients might suggest a common potential mechanism for the accelerating effect of obesity on the development of tumor burden in the obese.

"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. 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 approach for studying obesity in retrospective data sets [of patients with cancer]," says Dr. Sai Yendamuri, M.D., from Rosewell Comprehensive Cancer Cancer in Buffalo, N.Y., who led the study.

The study thereby highlights the fact that visceral obesity is associated with overall poor and recurrence-free survival in patients with early NSCLC. Hence the continued efforts to better predict lung cancer outcomes aids in the development of novel therapeutic approaches to prevent or control early-stage lung cancers

Source-Medindia