e20607 Background: The PD-1 inhibitors nivolumab and pembrolizumab are approved for the treatment of advanced non-small cell lung cancer (NSCLC), but little is known about patterns of disease progression when these agents fail. Understanding patterns of failure is key to developing strategies to improve duration of response to these agents. Methods: We gathered clinical and radiographic data on patients treated at the University of Michigan and the Ann Arbor VA for advanced NSCLC with standard-dose nivolumab (n = 68) or pembrolizumab (n = 23) after progression on platinum-based chemotherapy. Sites of disease progression were described as local (within the same lobe as primary disease), nodal (thoracic), or distant. Results: 91 patients were evaluable, of whom 56 (61.5%) had progression of disease after an average duration of therapy of 3.2 months (95%CI, 2.6-3.8). 10 (17.9%) patients had progression at local sites alone, 3 (5.4%) at nodal sites alone, 12 (21.4%) at distant sites alone, and 31 (55.4%) at a combination of sites. Overall, 41 (73.2%) had progression at distant sites. There was no statistically significant difference in clinical factors ( i.e. age, histology, comorbidity index) between progressors vs. non-progressors or distant-progressors vs. non-distant progressors. Of 37 patients who had prior radiation, 17 (45.9%) had progression at an irradiated site, with patients who had local and/or nodal progression more likely to have received radiation at site of progression (p = 0.01). The most common distant sites of progression were liver (13), bone (10), and brain (9). Conclusions: The most common site of disease progression was distant, with the liver being the most commonly involved site. This may be due to the immunotolerogenic environment of the liver, which is characterized by high IL-10 concentration and propagation of suppressive regulatory T cells, which can dampen activation of cytotoxic T cells. Prior irradiation did not seem to prevent disease progression. Our preliminary analysis suggests that the efficacy of checkpoint inhibitors is hindered in immune-privileged sites. Strategies to overcome immune tolerance should be investigated to improve duration of response to these agents.
U.S. Food and Drug Administration Approval Summary: Ramucirumab for the Treatment of Metastatic Non‐Small Cell Lung Cancer Following Disease Progression On or After Platinum‐Based Chemotherapy