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Chest Imaging

E2383. Immunotherapy: Current Use, Understanding Response Patterns on Imaging, and Future Developments

Szaflarski D1,  Azimov N1,2,  Pasquarella A1,  Schneider J1,  Hoffmann J.1 1. Winthrop University Hospital, Mineola, NY; 2. Stony Brook School of Medicine, Stony Brook, NY

Address correspondence to J. Hoffmann (jasonchoffmann@yahoo.com)

Background Information: The development of immunomodulatory agents, specifically the category of immune checkpoint inhibitors, has led to a new class of cancer medications that recently have been used to treat non–small-cell lung cancer, lymphoma, and melanoma. These agents have been developed to boost the body’s immune system in the fight against cancer. Over the past 1–2 years, data have emerged about multiple new agents, including response patterns on imaging and overall utility. Oncologic response is typically based on a reduction in size of the tumor and absence of new tumor, in accordance with classification systems such as Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST, and World Health Organization (WHO). However, immunotherapy agents can lead to pseudo progression on initial follow-up studies, with overall decrease in tumor burden on later follow-up imaging. This educational exhibit reviews the currently available data on these new agents, with a focus on the four response patterns that can be seen with treatment, as these differ substantially from classic response criteria and concepts typically used by radiologists.

Educational Goals/Teaching Points: Immunotherapy is a promising addition to the oncologic armamentarium. Radiologists must understand the concepts behind immunotherapy and the associated treatment response patterns that are specific to these agents. New or enlarging lesions in patients who have recently started immunotherapy do not always equate to disease progression. An initial increase in tumor size after initiating immunotherapy can be due to increase in tumor while the body begins to mount an immune response, or from immune cell infiltration in the tumor.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: This educational exhibit reviews key concepts about the immune system, as well as the history, development, mechanism of action, and current use of immunotherapy agents, including relevant literature review. This in-depth, image-rich review demonstrates imaging findings of patients on immunotherapy and educates radiologists on specific imaging patterns and responses, with a focus on the four major treatment response patterns. These patterns differ substantially from what radiologists typically consider as standard evaluation tools, such as RECIST, mRECIST, and WHO criteria. In addition, we review pathophysiology behind each of these treatment response patterns and discuss the causes of immune-related adverse events and their associated imaging findings. We provide supporting data and imaging from our institution regarding the use of these drugs in various cancers (including lung, lymphoma, and melanoma).

Conclusion: As immunotherapy drugs are being used more frequently in oncology patients, it is imperative for radiologists to understand this newer class of agents, the four major treatment response patterns on imaging, and why they may not fit into standard image-response criteria such as RECIST or mRECIST. Knowledge of these drugs and response patterns will allow for appropriate image interpretation, specifically so that pseudo progression is not misconstrued as short-term progression.