Outcomes in Patients With Metastatic Lung Cancer Receiving PD-1/PD-L1 Inhibitors With Thoracic Radiotherapy

Key Points

  • Thoracic radiotherapy was not associated with a higher risk of pneumonitis or other symptomatic immune-related adverse events in patients with metastatic lung cancer treated with PD-1 or PD-L1 inhibitors.
  • Thoracic radiotherapy was associated with a nonsignificant reduction in the risk of all-cause mortality. 

In a research letter to JAMA Oncology, Hwang et al detailed the outcomes of patients with metastatic lung cancer receiving an inhibitor of programmed cell death protein 1 (PD-1) or its ligand (PD-L1) with or without thoracic radiotherapy at Massachusetts General Hospital.

Study Details

The analysis included 164 patients treated between 2013 and 2016; 158 had non–small cell lung cancer and 6 (5%) had small cell lung cancer. Of them, 73 received thoracic radiotherapy and 91 did not; the 2 groups had similar baseline characteristics except for a lower proportion of patients in the radiotherapy cohort having adenocarcinoma (49% vs 75%) and targetable mutations (EGFR/ALK/ROS1; 4% vs 16%). Outcomes of interest were immune-related adverse events and survival.

Immune-Related Adverse Events

There were no significant differences between the radiotherapy group and the no-radiotherapy group with regard to the rates of grade ≥ 2 immune-related adverse events (13.7% vs 15.4%, P = .83), any-grade pneumonitis (8.2% vs 5.5%, P = .54), or grade ≥ 2 pneumonitis (4.1% vs 3.3%, P > .99). In the radiotherapy group, the median radiotherapy dose was similar in those patients who did vs did not develop pneumonitis (52.8 vs 50.4 Gy, P = .76). Of the 73 patients, 57 were treated with radiotherapy before checkpoint inhibitor initiation; pneumonitis did not occur in any of the 16 patients receiving radiotherapy between checkpoint inhibitor cycles or after treatment or receiving more than 1 course of radiotherapy.

Survival Findings

In the entire group, median overall survival was 12.1 months. On a multivariate analysis, all-cause mortality was lower in patients with grade ≥ 2 immune-related adverse events (hazard ratio [HR] = 0.45, P = .03) and in those receiving fewer chemotherapy lines (HR as continuous variable = 1.21, P = .01). Receipt of thoracic radiotherapy was associated with a nonsignificant reduction in all-cause mortality (HR = 0.66, P = .06).

The investigators concluded: “[P]ending prospective validation, our results suggest that [thoracic radiotherapy] does not significantly increase the risk of symptomatic [immune-related adverse events], including pneumonitis, compared with [checkpoint inhibitors] alone.”

Florence K. Keane, MD, of the Department of Radiation Oncology, Massachusetts General Hospital, is the corresponding author of the JAMA Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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