Pan-tumor analysis to investigate the obesity paradox in immune checkpoint blockade

Background: Obesity is a risk factor for developing cancer but is also associated with improved outcomes after treatment with immune checkpoint inhibitors (ICIs), a phenomenon called the obesity paradox. To interrogate mechanisms of divergent immune responses in obese and non-obese patients, we examined the relationship among obesity status, clinical responses, and immune profiles from a diverse, pan-tumor cohort of patients treated with ICI-based therapy.

Methods: From June 2021 to March 2023, we prospectively collected serial peripheral blood samples from patients with advanced or metastatic solid tumors who received ICI as standard of care at Johns Hopkins. Patients were stratified by obesity status at treatment initiation, with obesity defined as body mass index (BMI)≥30 at treatment initiation and BMI≥18.5 and <30 considered non-obese; underweight patients (BMI<18.5) were excluded. We evaluated the concentration of 37 cytokines and used cytometry by time of flight to characterize immune cell clusters and cell-surface expression markers at baseline and on-treatment.

Results: We enrolled 94 patients, of whom 30 (32%) were obese and 64 (68%) were non-obese. Compared with non-obese patients, obese patients had superior progression-free survival (HR: 0.44 (95% CI: 0.24 to 0.81), p=0.01) and overall survival (OS) (HR: 0.24 (95% CI: 0.07 to 0.80), p=0.02). Obese patients had lower serum IL-15 levels at treatment baseline and lower on-treatment levels of IL-6, IL-8, and IL-15. Low on-treatment IL-6 was associated with improved OS (HR: 0.27 (95% CI: 0.08 to 0.88), p=0.03), as was low on-treatment IL-8 (HR: 0.19 (95% CI: 0.05 to 0.70), p=0.01). Obese patients demonstrated lower levels of T effector cells with reduced expression of cytotoxicity markers and higher expression of exhaustion markers at baseline and on-treatment.

Conclusions: Obese and non-obese patients with cancer have divergent immunological responses to ICIs. Obesity is associated with reduced levels of certain inhibitory cytokines and higher expression of T-cell exhaustion markers. ICI-based therapy may more effectively reverse T-cell dysfunction in obese patients, potentially contributing to the paradoxically improved responses in this population.