Risk factors for pneumonitis after the combination treatment of immune checkpoint inhibitors and thoracic radiotherapy.

Abstract

Background: The combination of immune checkpoint inhibitors (ICIs) and thoracic radiotherapy (TRT) has played a significant role in the improvement of tumor therapy, but the increased incidence of pneumonitis has greatly limited its application. To identify potential intervention targets, we analyzed risk factors for pneumonitis after combination therapy with ICIs and TRT.

Methods: Overall, 335 patients who received TRT and ICI therapy concurrently or sequentially were included in our study. Pneumonitis was assessed and the related factors were analyzed.

Results: After combined TRT and ICI therapy, among the 335 patients, 219 (65.4%) patients had no pneumonitis or Grade 1 pneumonitis, 77 (23.0%) patients had Grade 2 pneumonitis, and 39 (11.6%) patients had Grade 3 or above pneumonitis. The incidence of Grade 2 or above pneumonitis was significantly related to the patients' age at diagnosis, sex, time interval and ipsilateral or bilateral lung dose‒volume parameters.

Conclusion: We first showed that older, male patients are more likely to suffer from pneumonitis of Grade 2 and above. We also found that, numerically, patients who received ICIs before radiotherapy (RT) were more likely to have pneumonitis than those who received RT before ICIs. Moreover, a longer interval between treatments, lower mean lung dose (MLD) and smaller ipsilateral or bilateral lung dose‒volume parameters are correlated with a lower incidence of pneumonitis of Grade 2 or above.