The findings, published in JAMA Network Open, are the latest to parse the complex relationship between body mass index (BMI) and treatment in cancers that is sometimes called the “obesity paradox.” The researchers compared outcomes among patients with normal weight, overweight, and obesity.
While higher BMI is an established risk factor for many types of cancer and for cancer-specific mortality overall, studies in some cancers have shown that patients with higher BMI do better, possibly because excess BMI acts as a nutrient reserve against treatment-associated weight loss.
Methods and results
For their research, Sung Jun Ma, MD, of Roswell Park Comprehensive Cancer Center, Buffalo, N.Y., and colleagues looked at records for 445 patients (84% men, median age 61) at Dr. Ma’s institution with nonmetastatic head and neck cancer who underwent chemoradiotherapy between 2005 and 2021. Patients were followed up for a median 48 months, and those with underweight at treatment initiation were excluded.
The researchers found that overweight BMI (25-29.9 kg/m2) was associated with improved overall survival at 5 years (71% vs. 58% of patients with normal weight), as well as 5-year progression-free survival (68% vs. 51%). No overall or progression-free survival benefit link was seen in patients with a BMI of 30 or higher, in contrast to some previous studies of patients with head and neck cancers. BMI was not associated with improved survival outcomes among human papillomavirus–positive patients.
Both overweight and obesity were associated with complete response on follow-up PET-CT, with nearly 92% of patients with overweight and 91% of patients with obesity (defined as having a BMI of 30 or higher) seeing a complete metabolic response, compared with 74% of patients with normal weight.
Having an overweight BMI was also associated with improvements in tumor recurrence, with fewer of patients with this type of BMI experiencing 5-year locoregional failure than patients with normal weight (7% vs 26%). Having an obese BMI was not associated with improvements in recurrence. All the reported differences reached statistical significance.
The study authors surmised that the discrepancies between outcomes for patients with overweight and obesity “may be due to a nonlinear association between BMI and survival, with the highest survival seen in the overweight BMI range.”
It was important to note that this study saw no differences in treatment interruptions between the BMI groups that could account for differences in outcomes. Only three patients in the cohort saw their radiotherapy treatment interrupted, Dr. Ma said in an interview.
“If we felt that the obesity paradox happens because people with normal BMI lose too much weight during the treatment course, treatment gets interrupted, and they get worse outcomes from suboptimal treatments, then we would have seen more treatment interruptions among those with normal BMI. However, that was not the case in our study,” he said. Rather, the results point to “a complex interaction among cancer, [a person’s build], and nutritional status.”
Clinicians should be aware, Dr. Ma added, “that the same head and neck cancer may behave more aggressively among patients with normal BMI, compared to others with overweight BMI. Patients with normal BMI may need to be monitored more closely and carefully for potentially worse outcomes.”
The investigators acknowledged several weaknesses of their study, including its retrospective design, the measure of BMI using cutoffs rather than a continuum, and the collection of BMI information at a single time point. While 84% of patients in the study received cisplatin, the study did not contain information on cumulative cisplatin dose.