Long-Term Survival With Pembrolizumab Re-administration After Pseudo-Progression With Immune-Related Interstitial Lung Disease in a Patient With Non-small Cell Lung Cancer

Immune checkpoint inhibitors may cause specific immune-related reactions, such as pseudo-progression. In particular, malignant pleural effusion tends to worsen due to this phenomenon. However, the appropriate management in such cases is unclear. We report a 73-year-old man with advanced lung adenocarcinoma and malignant pleural effusion who developed pseudo-progression with immune-related interstitial lung disease (irILD) induced by pembrolizumab (Merck & Co., Kenilworth, NJ, USA). After managing them with steroid treatments and chemotherapy, pembrolizumab was re-administered. At the time of writing, 30 months have passed since the re-administration of pembrolizumab without disease progression. This clinical course conveys an appropriate management strategy for patients with pseudo-progression and irILD.