Clinical significance of 18F-FDG uptake in interstitial lung lesions in lung cancer patients with interstitial lung disease treated with immune checkpoint inhibitor therapy.

BACKGROUND

Patients with lung cancer (LC) complicated by interstitial lung disease (ILD) exhibit an increased incidence of immune-related adverse event associated pneumonitis (irAEp), precipitating severe respiratory compromise and elevated morbidity. Predictive biomarkers for irAEp in this high-risk cohort remain limited. This study evaluated whether fluorine-18 2 -fluoro-2-deoxy-d-glucose (18F-FDG) uptake within ILD lesions serves as a prognostic factor for irAEp during immune checkpoint inhibitor (ICI) therapy.

METHODS

A retrospective cohort of 42 patients with LC complicated by ILD who received ICI between August 2015 and March 2024 at the Kumamoto University Hospital was evaluated. 18F-FDG uptake was quantified using the interstitial lung-to-liver (I/L) ratio, defined as the ratio of the maximum standardized uptake value (SUVmax) of contralateral ILD lesions to the mean SUV of the liver (SUVaverage), Associations with irAEp onset were evaluated using univariable and multivariable analyses.

RESULTS

Eleven patients developed irAEp. The median I/L ratio was 0.692 [95% confidence interval (CI) 0.580-0.741]. Patients with irAEp exhibited significantly elevated I/L ratios compared with non-irAEp patients (median: 0.740, 95%CI 0.692-0.874 vs. 0.608, 95%CI 0.545-0.735, P = 0.039). Multivariable analysis demonstrated that a higher I/L ratio category was significantly associated with irAEp onset (odds ratio: 6.228, 95%CI: 1.094-35.454, P = 0.039).

CONCLUSIONS

Elevated I/L ratio may serve as a predictive factor for irAEp in patients with LC and ILD treated with ICIs, supporting the potential role of 18F-FDG PET imaging in risk stratification and monitoring strategies for this high-risk population.