A Prospective Trial Evaluating the Safety and Systemic Response From the Concurrent Use of Radiation Therapy with Checkpoint Inhibitor Immunotherapy in Metastatic Non-Small Cell Lung Cancer

Abstract

Introduction/background: This study assessed the safety and systemic (abscopal) response from the addition of local stereotactic body radiation therapy (SBRT) to checkpoint inhibitor (CPI) immunotherapy in patients with metastatic non-small cell lung cancer.

Patients/methods: Thirty-five patients with at least 2 sites of measurable disease on PET/CT received standard-of-care CPI immunotherapy alone (n = 19), or in combination with 4 cycles doublet carboplatin/pemetrexed chemotherapy (n = 16), and 3 to 5 fractions SBRT to a single extracranial target lesion between cycles 1 to 2 of the systemic therapy. Adverse events were assessed using CTCAE version 5.0. Best systemic objective response rate (ORR) was assessed using iRECIST criteria, excluding any irradiated lesion(s). Additional SBRT to a different target lesion was offered to patients who continued on immunotherapy with unconfirmed progressive disease or mixed response.

Results: Fifteen patients (44%) experienced 22 grade 1 to 2 toxicities potentially attributable to radiation, most commonly pneumonitis (n = 9) and fatigue (n = 6), and no grade 3 to 5 radiation-induced toxicities. Patients undergoing combined CPI-chemotherapy received a lower median biologically effective dose of SBRT than those undergoing CPI monotherapy (43.2 vs. 60Gy), but had a higher rate of radiation-induced toxicity (56% vs. 32%, P < .01). The best systemic ORR was 53%, with 20.5% stable disease and 26.5% progressive disease. Fifteen patients underwent a subsequent course of SBRT based on their response, among which 3 (20%) had progression-free intervals of 12, 16, and 10 months thereafter.

Conclusions: Addition of SBRT to CPI immunotherapy (with/without chemotherapy) is safe. The favorable systemic response observed warrants further assessment with a randomized trial.

Trial registration: ClinicalTrials.gov NCT03137771 NCT03721341.

Keywords: Immune Checkpoint Blockers; Immune Checkpoint Inhibitor; Immunotherapy; Metastatic; Non–small cell lung cancer; PD-L1 inhibitor; Programmed Death-Ligand 1 Inhibitors; Radiation therapy; Radiobiology.

Conflict of interest statement

Declarations of Interest

Malcolm D. Mattes has no conflicts of interest. Timothy D. Eubank has no conflicts of interest. Mohammed Almubarak has no conflicts of interest. Sijin Wen has no conflicts of interest. Gary Marano has no conflicts of interest. Geraldine M. Jacobson has no conflicts of interest. Patrick C. Ma is on the speaker’s bureau for Merck, AstraZeneca, Bayer, Bristol-Myers Squibb; he also is on the advisory board (Ad hoc) for AstraZeneca and Apollomics.

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