SSTR2 and neoplasm: More than 50% of the published cases had progressive disease after PRRT (i.e., did not respond to PRRT), despite these pituitary tumours had, in general, a significant expression of SSTRs on functional imaging prior to PRRT [93,96,111], suggesting that other properties than tumour surface SSTR2 expression and binding are needed for the tumouricidal effects of PRRT.