2150 - Optimal Timing of Immunoradiotherapy: Immune Checkpoint Inhibitor before or after Radiation Therapy?

H. Tanaka, A. Hironaka, C. Nakabe, M. Karita, K. Ueda, T. Ono, M. Kajima, Y. Manabe, K. Fujimoto, and T. Shiinoki; Yamaguchi University Graduate School of Medicine, Department of Radiation Oncology, Ube, Japan

Purpose/Objective(s): In recent years, the number of cases in which immune checkpoint inhibitors (ICI) have been administered to patients with stage IV non-small cell lung cancer (NSCLC) has increased dramatically. It is reported that antigens released from tumors by radiation therapy (RT) enhance the effects of subsequent ICI. In this study, we investigated whether overall survival (OS) rates varied depending on the presence or absence and timing of ICI administration among patients with stage IV NSCLC who underwent palliative RT. Materials/

Methods: Eighty-one patients with NSCLC (70 male, 11 female) who underwent palliative RT were enrolled in this study. The median age of the patients was 70 (range, 43–88) years. Patients were diagnosed with adenocarcinoma (49), squamous cell carcinoma (22), NSCLC, not otherwise specified (7), large cell carcinoma (2), and pleomorphic carcinoma (1 patient). The median irradiated BED₁₀ was 39 (range, 27.3–72.0) Gy. The irradiated sites included bone (50), brain (14), mediastinum (8), and other sites (9 patients). ICI were administered to 45 patients (55.5%). Of these, 19 patients were administered ICI before RT, 25 patients were administered ICI after RT, and 1 patient was administered ICI both before and after RT.
Results: The mean follow-up period was 8 (range, 1–52) months, during which 57 patients died. There was a significant difference in OS among patients without ICI use, ICI use before RT, and ICI use after RT (p < 0.001). The 6-month OS rate for these groups was 22.7%, 48.8%, and 86.3%, respectively. Univariate analysis using the Cox proportional hazards model showed that sex (male vs. female), performance status (0–1 vs. 2–4), BED₁₀ (=39 Gy vs. <39 Gy), and ICI use after RT (presence vs. absence) were significant prognostic factors for OS (Table). In multivariate analysis, only ICI use after RT was an independent significant factor.
Conclusion: Our study suggests that ICI administration after palliative RT improves the OS of patients with stage IV NSCLC. Abstract 2150 – Table 1

Variables		Univariate		Multivariate
		Hazard ratio (95% CI)	p value	Hazard ratio (95% CI)	p value
Sex	Male vs. female	0.427 (0.204–0.891)	0.023	0.774 (0.350–1.71)	0.526
Histology	Others vs. adenoca.	1.494 (0.880–2.537)	0.138
Age (years)	< 70 vs. = 70	1.259 (0.743-2.132)	0.392
Performance status	2-4 vs. 0-1	1.890 (1.062-3.365)	0.031	1.330 (0.732-2.415)	0.349
BED10 (Gy)	< 40 vs. = 40	2.019 (1.026-3.971)	0.042	1.334 (0.637-2.794)	0.445
Irradiated site	Others vs. bone	1.412 (0.832-2.395)	0.201
Other mets	presence vs. absence	1.551 (0.700-3.437)	0.279
ICI use after RT	presence vs. absence	0.228 (0.115-0.453)	<0.001	0.259 (0.127-0.528)	<0.001