Safety Related to the Timing of Radiotherapy and Immune Checkpoint Inhibitors in Patients with Advanced Non-Small Cell Lung Cancer: A Single Institutional Experience

Background: The safety impact of radiotherapy (RT) timing relative to immune checkpoint inhibitors (ICIs) for advanced non-small-cell lung cancer (NSCLC) is unclear. We investigated if RT within 14 days (Interval 1) and 90 days (Interval 2) of ICI use is associated with toxicities compared to RT outside these intervals. Methods: Advanced NSCLC patients treated with both RT and ICIs were reviewed. Toxicities were graded as per CTCAE v4.0 and attributed to either ICIs or RT by clinicians. Associations between RT timing and Grade ≥2 toxicities were analyzed using logistic regression models adjusted for patient, disease, and treatment factors (α = 0.05). Results: Sixty-four patients were identified. Twenty received RT within Interval 1 and 40 within Interval 2. There were 20 Grade ≥2 toxicities in 18 (28%) patients; pneumonitis (6) and nausea (2) were most prevalent. One treatment-related death (immune encephalitis) was observed. Rates of patients with Grade ≥2 toxicities were 35%/25% in the group with/without RT within Interval 1 and 30%/25% in the group with/without RT within Interval 2. No significant association between RT timing relative to ICI use period and Grade ≥2 toxicities was observed. Conclusion: Albeit limited by the small sample size, the result suggested that pausing ICIs around RT use may not be necessary.