New Study Highlights Impact of Obesity on Survival in Advanced NSCLC Patients Treated with Immunotherapy

New research offers insights into the relationship between obesity and overall survival in patients undergoing immunotherapy for advanced non-small cell lung cancer (NSCLC). The study, published August 2, 2024 in JAMA Network Open, suggests that conventional chemotherapy may be a better option than immunotherapy for patients with obesity.

Obesity is an important modifiable risk factor for developing cancer, second only to tobacco use. Obesity is traditionally defined as having a body mass index (BMI) of 30 kg/m2 or greater, while a BMI of 25 up to 30 kg/m2 is considered overweight.

Interestingly, some past observational studies have found that, among patients receiving treatment for cancer, those with higher BMIs tend to have better survival rates compared to patients of normal weight. This pattern, known as the obesity paradox, has been observed in patients undergoing both conventional chemotherapy and treatment with immune checkpoint inhibitors (ICIs)—a type of immunotherapy.

However, there has been a lack of studies comparing the impact of BMI on overall survival in cancer patients with obesity who receive either ICI immunotherapy or conventional chemotherapy. As such, it is unclear which treatment is best as a first-line option for patients with advanced NSCLC and obesity or overweight.

To examine the relationship between BMI and survival rates in this group, a retrospective cohort study was conducted by Yasutaka Ihara, Pharm.D. and colleagues at the Osaka Metropolitan University in Osaka, Japan.

The researchers analyzed the medical records of more than 31,000 adult patients with advanced NSCLC who received conventional chemotherapy or ICI treatment at various treatment centers in Japan. They focused on patients who began treatment between December 2015 and January 2023 and excluded those with incomplete BMI data or certain other treatments.

Statistical analysis was used to compare survival outcomes based on BMI, adjusting for various factors like age, sex, and other health conditions. The primary outcome was overall survival, and the survival analysis included a 3-year follow-up period after the first-line chemotherapy.

The results showed that for patients with a BMI below 28, immunotherapy was associated with a lower risk of death compared to conventional chemotherapy. However, for patients with a BMI of 28 or higher, this benefit was not observed.

The authors acknowledged that their study had some limitations. The data used were from routine clinical practice, not designed for research, so a randomized trial wasn't possible. Obesity was measured using BMI, which doesn't distinguish between muscle and fat, potentially overlooking the survival benefit seen in patients with higher muscle mass. The study also lacked data on out-of-hospital deaths and specific biomarker status, which could affect treatment choices. Additionally, BMI was treated as a continuous variable, which might introduce statistical errors, and the findings, based on a Japanese population, may not apply to other groups.

In their paper, the authors encourage healthcare professionals to consider BMI during treatment planning. They concluded “that ICI therapy may not necessarily be the optimal first-line therapy for patients with overweight or obesity, and the use of conventional chemotherapy should also be considered.”