A panoply of clinical factors has been evaluated as “predictors” of PRRT response. Factors that predict clinical outcomes and survival have been misperceived as predictors of PRRT response. Thus, performance status, primary location, and disease extent are all prognostic and unrelated to the prediction of PRRT response. Similarly, glucose-based metabolism (FDG-positive) and tumor grade are also prognostic features. Circulating monoanalyte biomarkers, if elevated, reflect tumor burden, and are prognostic. Other parameters such as somatostatin receptor imaging intensity or IHC SSTR expression provide evidence of target existence and properly are “inclusion” factors. They cannot predict PRRT response but represent indices of target acquisition likelihood.
CgA = chromogranin A; IHC = immunohistochemistry; KPS = Karnofsky performance score; NSE = neuron-specific enolase; ORR = objective response rate; OS = overall survival; PFS = progression free survival; SSTR = somatostatin receptor; IHC= immunohistochemical
(Figure adapted from Bodei et al. EJNMMI 2018; 45(7): 1155–69).