Nivolumab‐induced radiation recall pneumonitis in non‐small‐cell lung cancer patients with thoracic radiation therapy

The role of previous thoracic radiation therapy as a risk factor of immune‐related pneumonitis is unclear. Furthermore, some patients develop radiation recall pneumonitis, which is characterized by a radiation pneumonitis‐like imaging pattern with consolidation progressing within a previous radiation field. In this multicenter retrospective study, we analyzed the relationship of previous thoracic radiation therapy with immune‐related pneumonitis and the characteristics of radiation recall pneumonitis. The medical records of patients with non‐small‐cell lung cancer who had received nivolumab between December 2015 and March 2017 at five institutions were retrospectively reviewed. Incidence, imaging patterns, clinical course, and risk factors of immune‐related pneumonitis and radiation recall pneumonitis were evaluated. A total of 669 patients were evaluated, and the incidences of all‐grade and grade 3 or higher immune‐related pneumonitis were 8.8% and 2.6%, respectively. The incidences of immune‐related pneumonitis were 13.2% (34/257) and 6.1% (25/412) in patients with and those without previous thoracic radiation therapy, respectively. A history of previous thoracic radiation therapy was associated with immune‐related pneumonitis (odds ratio, 2.11; 95% confidence interval, 1.21–3.69 in multivariate analysis). Among the patients with previous thoracic radiation therapy, 6.2% (16/257) showed radiation recall pattern. This study found an increased risk of nivolumab‐induced immune‐related pneumonitis associated with a history of thoracic radiation therapy. Radiation recall pattern was one of the major patterns of immune‐related pneumonitis among the patients with previous thoracic radiation therapy. Incidence, risk factors, and clinical outcome of radiation recall pneumonitis were elucidated. The study revealed thoracic radiation therapy as a risk factor of immune‐related pneumonitis. The characteristic imaging pattern “radiation recall pneumonitis” occurred in patients with previous radiation therapy. The incidence of this characteristic pneumonitis contributed to the higher risk of immune‐related pneumonitis in patients with a history of thoracic radiation therapy.