Fig. 1 ∣. Early FDG PET/CT predicts response to immunotherapy and is correlated with peripheral blood data.

a, Schematic of the hypothetical response to cancer immunotherapy, graphed as a function of change in tumor SUV_MAX as measured by FDG PET/CT versus time. Dotted lines represent the threshold for a MF and MR, respectively. b, Waterfall plot of change in tumor SUV_MAX, between baseline (PET0) and early post-treatment (PET1) FDG PET/CT scans, according to treatment response. Dotted lines represent +70% and −30% change in SUV_MAX, respectively. c, Maximum intensity projection (MIP) FDG PET/CT images of two patients at baseline and 1 week after starting pembrolizumab. Patient 5 (top) had an interval drop in SUV_MAX in a left neck metastasis representative of a metabolic response (change in SUV_MAX = −70.7%). Patient 3 (bottom) had an interval increase in SUV_MAX across multiple lesions representative of a metabolic flare (change in SUV_MAX = 114%). Both patients went on to have a complete response to therapy. d, Analysis of Ki67+ CD8 T cells in peripheral blood at the indicated times in patients with a metabolic response (patients 4 and 5) and metabolic flare (patient 3), a responding patient with stable metabolism (patient 7), and nonresponding patients with stable metabolism (patients 13–16, 18). SUV_MAX, maximal standardized uptake value; CR, complete response; PR, partial response; PD, progressive disease.