Concurrent immunotherapy and re‐irradiation utilizing stereotactic body radiotherapy for recurrent high‐grade gliomas

BACKGROUND: Clinical trials evaluating immune checkpoint inhibition (ICI) in recurrent high‐grade gliomas (rHGG) report 7%–20% 6‐month progression‐free survival (PFS), while re‐irradiation demonstrates 28%–39% 6‐month PFS. AIMS: We evaluate outcomes of patients treated with ICI and concurrent re‐irradiation utilizing stereotactic body radiotherapy/fractionated stereotactic radiosurgery (SBRT) compared to ICI monotherapy. METHODS AND RESULTS: Patients ≥18‐years‐old with rHGG (WHO grade III and IV) receiving ICI + SBRT or ICI monotherapy between January 1, 2016 and January 1, 2019 were included. Adverse events, 6‐month PFS and overall survival (OS) were assessed. Log‐rank tests were used to evaluate PFS and OS. Histogram analyses of apparent diffusion coefficient maps and dynamic contrast‐enhanced magnetic resonance perfusion metrics were performed. Twenty‐one patients with rHGG (ICI + SBRT: 16; ICI: 5) were included. The ICI + SBRT and ICI groups received a mean 7.25 and 6.2 ICI cycles, respectively. There were five grade 1, one grade 2 and no grade 3–5 AEs in the ICI + SBRT group, and four grade 1 and no grade 2–5 AEs in the ICI group. Median PFS was 2.85 and 1 month for the ICI + SBRT and ICI groups; median OS was 7 and 6 months among ICI + SBRT and ICI groups, respectively. There were significant differences in pre and posttreatment tumor volume in the cohort (12.35 vs. 20.51; p = .03), but not between treatment groups. CONCLUSIONS: In this heavily pretreated cohort, ICI with re‐irradiation utilizing SBRT was well tolerated. Prospective studies are warranted to evaluate potential therapeutic benefits to re‐irradiation with ICI + SBRT in rHGG.