Incidence of Immune Checkpoint Inhibitor-Related Pneumonitis in Lung Cancer

I read with interest the study in CHEST (August 2021) by Atchley et al1Atchley W.T. Alvarez C. Saxena-Beem S. et al.Immune checkpoint inhibitor-related pneumonitis in lung cancer.Chest. 2021; 160: 731-742Google Scholar, where they looked at the “real world” incidence of immune checkpoint inhibitor-related pneumonitis (ICI-P) in lung cancer. They observed an incidence of 9.5%, which is significantly higher than the 3% to 5% usually reported in literature. This finding has potentially great significance because approximately 12% of ICI-P will not respond to therapy. Even in the responders, there is approximately a 25% risk of recurrence.2Naidoo J. Wang X. Woo K.M. et al.Pneumonitis in patients treated with anti-programmed death 1/programmed death ligand 1 therapy.J Clin Oncol. 2017; 35: 709-717Google Scholar However, there are some issues with the design that are probably inherent in any study in which the clinical diagnosis is made retrospectively. The authors did a medical records review and diagnosed 30 cases of ICI-P. They further classified these into three groups based on the degree of diagnostic certainty: definite, probable, and possible. The “possible” group included patients with radiologic features consistent with ICI-P, but who likely had other pulmonary diseases such as volume overload, infection. or radiation pneumonitis. This is problematic because ICI-P by definition, is a diagnosis of exclusion. There are no characteristic radiologic features, and patients can present with a wide range of CT findings.3Delaunay M. Cadranel J. Lusque A. et al.Immune checkpoint inhibitors associated with interstitial lung disease in cancer patients.Eur Respir J. 2017; 50: 1700050Google Scholar Many of these findings can also be seen in pulmonary infections or pulmonary edema. Also, the authors do not mention how many of the 30 cases were from the “possible” group. If this number is large, then it is a major limitation of the study. Immune Checkpoint Inhibitor-Related Pneumonitis in Lung Cancer: Real-World Incidence, Risk Factors, and Management Practices Across Six Health Care Centers in North CarolinaCHESTVol. 160Issue 2PreviewIn this cohort, ICI-P was more common and severe than previously reported and carried an unexpectedly high mortality rate. Risk for ICI-P was shown to be independently associated with several chronic pulmonary diseases, which may account for the higher incidence of ICI-P in patients with lung cancer. Full-Text PDF ResponseCHESTVol. 161Issue 3PreviewWe thank Dr Poulose for his interest in our study on the incidence and risk factors for the development of immune checkpoint inhibitor-related pneumonitis (ICI-P) in patients with lung cancer.1 Dr Poulose points out that the “possible’’ group included patients with other pulmonary diseases such as volume overload, infection, or radiation pneumonitis at the time of the ICI-P diagnosis. He further states that this is problematic because by definition; ICI-P is a diagnosis of exclusion. In the article, we believe we addressed how the diagnosis of ICI-P can be confounded by comorbid conditions that develop in patients who receive immune checkpoint inhibitors. Full-Text PDF