ES17.03 Imaging of Pneumonitis

Pneumonitis is one of the major adverse events from systemic anti-cancer therapy and provides clinical challenges in oncology practice. Imaging plays a key role in detection, diagnosis, and monitoring of pneumonitis in cancer patients. This lecture will discuss 1) diagnosis and monitoring of pneumonitis using CT patterns on imaging, 2) spectrum of CT patterns of pneumonitis focusing on immune-checkpoint inhibitors (ICI) and epidermal growth factor receptor (EGFR) inhibitors, and 3) emerging challenges and pitfalls in the era of COVID-19 pandemic. When approaching pneumonitis on imaging, it is very important to note that pneumonitis represents lung’s response to injury. The lung’s response patterns to injury has several histologic manifestations with corresponding CT patterns, which are originally described in idiopathic interstitial pneumonias and are also noted in the setting of pneumonitis secondary to cancer therapy. The assessment of extent and distribution of the lung abnormalities on CT is very important to recognize the distinct CT patterns. The spectrum of CT patterns is noted in pneumonitis from cancer therapies, and are associated with clinical severity of pneumonitis. Recognition of CT patterns helps to diagnosis, monitor, and prognosticate pneumonitis in cancer patients. In terms of pneumonitis from individual agents, the lecture will focus on pneumonitis from ICI and EGFR inhibitors, which are two representative agents used in lung cancer that can cause pneumonitis. ICI pneumonitis is relatively rare, but clinically serious and potentially life-threatening toxicity from ICI therapy, and is a leading cause of anti-PD-1/PD-L1-related deaths. The incidence of ICI pneumonitis is higher in lung cancer than in other cancers, indicating that pneumonitis is a particularly important issue in patients with lung cancer. The representative CT patterns of ICI pneumonitis include AIP/ARDS pattern, COP pattern, NSIP pattern, and HP pattern. Among these patterns, COP pattern is most common, noted in about two thirds of the patients. AIP/ARDS patten has the most severe clinical presentation and requires immediate clinical attention. The details of each of these CT patterns will be described with case presentations to demonstrate the characteristic features with clinical correlation. Pneumonitis is also a recognized class-effect for EGFR inhibitors. A higher incidence rate in Japanese population is noted, with a high mortality rate in the cohort studies from Japan, which is confirmed by the recent meta-analysis of 153 EGFR inhibitor trials in non-small cell lung cancer. The spectrum of CT patterns is also noted in EGFR inhibitor pneumonitis, and correlates with clinical severity and outcome. As the emerging issues with the advances of cancer therapies and the recent COVID pandemic, pneumonitis from combination ICI and radiotherapy is discussed, featuring the imaging manifestations from both ICI pneumonitis and radiation pneumonitis. Finally, the overlapping imaging features of ICI pneumonitis and COVID-19 pneumonia are presented, to demonstrate a unique challenge in the era of COVID-19 pandemic. The lecture concludes emphasizing the importance of multidisciplinary approach to further understand these emerging challenges to optimize diagnosis and management of pneumonitis in cancer patients. Abbreviations: AIP = Acute Interstitial Pneumonia;ARDS = Acute Respiratory Distress Syndrome;COP = Cryptogenic Organizing Pneumonia;HP = Hypersensitivity Pneumonitis;NSIP = Non-Specific Interstitial Pneumonia References: Nishino M, Sholl LM, Hatabu H, Ramaiya NH, Hodi FS. Anti-PD-1 Related Pneumonitis during Cancer Immunotherapy. N Engl J Med. 2015 Jul 16;373(3):288-290. 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