Nevertheless, it is conceivable that volumetric PET measurements in this patient population could provide additional value due to several reasons: (1) volumetric parameters like PSMA-TV or TL-PSMA capture the overall tumor burden [31]; (2) the degree of PSMA uptake and extent of metastases have both been shown to be correlated with survival in metastatic CRPC [32]; (3) volumetric measurements can be reproducibly performed using commercially available software [20]; and (4) tumor volumetry on PET have achieved encouraging results in different cancers [33,34]. This evidence concerns the gene FOLH1 and cancer.