CAR T-cell therapy induced pseudoprogression

Pseudoprogression is defined as a seeming post-therapy increase in tumor burden on imaging that recedes on subsequent reimaging without additional therapy. The origins of pseudoprogression lie in the field of immunology with current understanding of the imaging finding coming mostly from experience with checkpoint inhibitors used for management of solid tumors. With the wider administration of chimeric antigen receptor (CAR) T-cell therapy for the treatment of hematologic malignancies, CAR T-cell induced pseudoprogression (CARTiPP) has also been noted although it has remained an underreported, although likely rare, adverse event lacking clear description and management guidelines. CARTiPP can obscure response assessment in patients and lead to serious clinical complications due to edema-driven compression of organs or tissue. This mini review summarizes the emergence of pseudoprogression with the rise of immunotherapy along with the modifications of radiologic guidelines for correct interpretation of scans as a key non-invasive technique for overcoming the associated diagnostic challenges. It discusses the limited available data on the nature of CARTiPP in the setting of the tumor microenvironment and its meaning for the care of patients receiving CAR T-cell therapy.