PHOENIX (FRONTLINE MEDICAL NEWS) Being underweight is associated with a substantially increased risk of complications following lung resection for cancer, results from a large database study found.

“This is not generally known among surgeons or their patients,” Dr. Trevor Williams said in an interview before the annual meeting of the Society of Thoracic Surgeons. “Studies are conflicting about the relationship of BMI [body mass index] to surgical outcomes. Most of the previous studies simply categorize BMI as overweight or not. We’ve stratified based on World Health Organization categories to get a more precise look at BMI.”

Dr. Williams, a surgeon at the University of Chicago Medical Center, and his associates evaluated 41,446 patients in the STS General Thoracic Surgery Database who underwent elective anatomic lung resection for cancer between 2009 and 2014. Their mean age was 68 years, and 53% were female. The researchers performed multivariable analysis after adjusting for validated STS risk model covariates, including gender and spirometry.

According to WHO criteria for BMI, 3% were underweight (less than 18.5 kg/m2); 33.5% were normal weight (18.5-24.9 kg/m2); 35.4% were overweight (25-29.9 kg/m2); 18.1% were obese I (30-34.9 kg/m2); 6.4% were obese II (35-39.9 kg/m2), and 3.6% were obese III (40 kg/m2 or greater). Dr. Williams and his associates observed that women were more often underweight, compared with men (4.1% vs. 1.8%, respectively; P less than .001), and underweight patients more often had chronic obstructive pulmonary disease (51.7% vs. 35.2%; P less than .001). Pulmonary complication rates were higher among underweight and obese III patients (P less than .001), while being underweight was also associated with higher rates of infections and any surgical complications.

Multivariable analysis revealed that pulmonary and any postoperative complications were more common among underweight patients (odds ratio, 1.44 and OR, 1.41, respectively), while any major complication was more common among obese III patients (OR, 1.18). Overweight and obese I-II patients were less likely to have any postoperative and pulmonary complications, compared with patients who had a normal BMI. “The finding of underweight patients being such a high-risk patient population is suggested in the literature but not demonstrated as clearly as in this study,” Dr. Williams said. “A truly surprising finding was that obese patients actually have a lower risk of pulmonary and overall complications than ‘normal’-BMI patients.”

He concluded that according to the current analysis, “careful risk assessment is appropriate when considering operating on underweight patients. Whether there are interventions that could be instituted to improve an individual’s risk profile has not been determined. Any preconceived notions about not operating on obese patients due to elevated risk appear to be unfounded.”

Dr. Williams reported having no financial disclosures.