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.