Combination of immune checkpoint inhibitors and radiotherapy for bone metastases induces an abscopal effect and improves outcomes in non‑small cell lung cancer

The combination of immune checkpoint inhibitors (ICIs) and radiotherapy (RT) improves outcomes in non-small cell lung cancer (NSCLC). However, the potential abscopal effect of RT for bone metastases (BoMs) remains unclear. The present retrospective study aimed to evaluate the impact of RT for BoMs on lung lesion response and survival in patients with NSCLC receiving ICIs. A total of 108 patients with NSCLC with BoMs treated with ICIs between March 2016 and January 2024 were included and divided into two groups based on whether they received RT for BoMs. Primary outcomes included the lung lesion response rate, overall survival (OS), progression-free survival (PFS) and incidence of immune-related adverse events (irAEs). Among 33 patients who received RT for BoM (RT-BoM group), the dose/fraction ranged from 2 to 8 Gy/1 to15 fx (total 8-39 Gy). The lung lesion response rate was significantly higher in the RT-BoM group than in the non-RT-BoM group (n=75; 42.4 vs. 21.3%; P=0.03). The median OS and PFS times were significantly longer in the RT-BoM group (24.9 vs. 16.3 months, P=0.01; 11.0 months vs. 6.2 months, P=0.03), while the incidence of irAEs was comparable (21.2 vs. 21.3%; P=0.99). The group that received RT before ICI initiation (n=22) had a significantly higher lung lesion response rate than the group that received RT after ICI initiation (n=11; 54.5 vs. 9.1%; P=0.02), with a trend toward prolonged OS and PFS. Multivariate analysis identified RT for BoMs as an independent predictor of lung response (P=0.02), OS (P=0.03) and PFS (P=0.02). RT for BoMs was associated with improved lung response and prognosis in patients with NSCLC receiving ICIs, suggesting a possible abscopal effect. Further validation in prospective studies with larger patient groups is warranted.