A 63-year-old female with lung adenocarcinoma treated with nivolumab, who experienced pseudoprogression. A 63-year-old female with lung adenocarcinoma treated with nivolumab, who experienced pseudoprogression. Comparing to the baseline (A), the patient experienced tumor burden increase at 1.4 months of therapy (B), meeting the criteria for progressive disease, which was confirmed on the serial CT scans (C). Subsequently, tumor regression to the baseline burden (+0%) was noted at 8.8 months of therapy (D). Mizuki Nishino et al. Clin Cancer Res 2017;23:5737-5744 ©2017 by American Association for Cancer Research