Efficacy and Safety of Chemoimmunotherapy in Patients With Advanced Non‐small Cell Lung Cancer With Pre‐existing Interstitial Pneumonia and Low PD‐L1 Expression

Background/Aim: Establishing the suitability of initiating immune checkpoint inhibitor (ICI) therapy in patients with lung cancer and coexisting interstitial pneumonia (IP) is challenging. Real-world evidence on the efficacy and safety of ICIs in such patients is urgently needed to inform clinical practice. Patients and Methods: This retrospective study evaluated the effects of ICI administered to 79 patients with advanced or recurrent non-small cell lung cancer (NSCLC) and programmed death ligand 1 (PD-L1) tumor proportion scores of 1-49%, who had pre-existing IP. These patients received first-line therapy comprising an ICI with chemotherapy or chemotherapy alone at 18 institutions in Japan between March 2017 and June 2022. Results: Twelve patients received ICI plus chemotherapy (chemoimmunotherapy group) as first-line treatment, and 67 received chemotherapy alone (chemotherapy group). Only brain metastases were significantly more frequent in the chemoimmunotherapy group; no other differences in patient backgrounds between the two groups were observed. Overall survival (OS) and progression-free survival did not differ between the two groups. After propensity score matching, chemoimmunotherapy significantly prolonged OS compared to chemotherapy alone (25.3 months vs. 9.6 months, p=0.033), without significant differences in incidences of severe adverse events, including pneumonitis. In the analysis of patients who received ICI up to second-line treatment, ICI therapy was associated with prolonged OS compared to non-ICI treatment (29.8 months vs. 16.3 months, p=0.012). Conclusion: Early use of immunotherapy for patients with advanced NSCLC with low PD-L1 expression and coexisting IP may improve prognosis.