FOLH1 and neoplasm: This study shows that change in total tumor burden at cycle 2 (i.e., PSMA-positive tumor volume or TTV, semi-automatically assessed by quantitated SPECT/CT acquired 48 h post-injection of the radiopharmaceutical at baseline and 6 weeks after treatment start) is able to predict overall survival in mCRPC patients receiving [177Lu]Lu-PSMA I&T therapy.