Radiographic Challenges and Considerations with Cancer Immunotherapy

BACKGROUND: With immune checkpoint inhibitor therapy, we observe new and challenging radiographic patterns such as hyperprogression and pseudoprogression. This begs the question - are there radiographic parameters that can predict response to immune checkpoint inhibitors? Historically, tumor burden has been considered an impediment to efficacy of immunotherapeutic agents, such as vaccines and allogeneic stem cell transplant. However, the association between tumor burden and efficacy of immune checkpoint inhibitors is unknown. We sought to determine the association between radiographic tumor burden parameters and efficacy of immune checkpoint inhibitors in advanced lung cancer. MATERIALS AND METHODS: We performed a retrospective analysis of patients with advanced lung cancer treated with immune checkpoint inhibitor monotherapy. Demographic, disease, and treatment data were collected. Serial tumor dimensions were recorded according to Response Evaluation Criteria in Solid Tumors 1.1. Associations between radiographic tumor burden (baseline sum of longest diameters [BSLD], longest single diameter) and clinical outcomes (radiographic response, progression-free survival, and overall survival) were determined using log-rank tests, cox proportional-hazard regression, and logistic regression. RESULTS: Among 105 patients, median baseline sum of longest diameters was 6.4 cm; median longest single diameter was 3.6 cm. BSLD was not associated with radiographic response, progression-free survival, or overall survival. In univariate and multivariate analyses, no significant associations were observed for the other radiographic parameters and outcomes when considered as categorical or continuous variables. CONCLUSIONS: Although tumor burden has been considered a mediator of efficacy of earlier immunotherapies, in advanced lung cancer it does not appear to impact outcomes from immune checkpoint inhibitors.