Programmed cell death 1 (PD-1) inhibitors have exhibited significant efficacy in various types of cancer including non-small-cell lung cancer (NSCLC). PD-1 inhibitors are expected to be used increasingly as monotherapy or in combination. Pneumonitis is relatively uncommon but potentially fatal toxicity induced by anti PD-1 therapy. Although patients with apparent interstitial pneumonia are excluded from clinical trials of anti PD-1 therapy, patients with minimal interstitial lung opacity on chest CT scans can be treated with PD-1 inhibitors in the clinical practice. Little is known about the incidence of pneumonitis in such cases.
Among patients with NSCLC treated with PD-1 inhibitors in our institution, we identified those who developed pneumonitis. We reviewed medical records and chest imaging studies. We investigated association between background factors including lung opacities on chest CT scan before anti PD-1 therapy and development of pneumonitis.
We analyzed a total of 79 patients treated with PD-1 inhibitors. At the baseline CT scan, ground glass opacities and reticular opacities were observed in 20 patients (25%) and 18 patients (23%), respectively. All of these interstitial opacities were very mild, and the case of obvious interstitial pneumonia was not observed. During the anti PD-1 therapy, pneumonitis developed in 16 patients (20%). Of the 20 patients with ground glass opacities, ten patients (50%) developed pneumonitis, and of the 18 patients with reticular opacities, nine patients (50%) developed pneumonitis. Ground glass opacities and reticular opacities at baseline were significantly associated with the incidence of pneumonitis (p < 0.001 and p = 0.001, respectively). Among the 49 patients who did not have either of these opacities, three patients (6%) developed pneumonitis. There were no association between pneumonitis and other background factors such as presence of radiation pneumonitis or pulmonary emphysema.
Ground glass opacities and reticular opacities on chest CT scan before treatment can be risk factors of pneumonitis, even if they are mild. For the patients without these opacities, anti PD-1 therapy appears relatively safe.
Clinical trial identification
Legal entity responsible for the study
Aichi Cancer Center Aichi Hospital.
Has not received any funding.
All authors have declared no conflicts of interest.