Peptide receptor radionuclide therapy with 177Lu-DOTATATE: The IEO phase I-II study

Purpose: Peptide receptor radionuclide therapy (PRRT) is used in tumours expressing type 2 somatostatin receptors (sst 2), mainly neuroendocrine. The aim of this prospective phase I-II study was to evaluate the toxicity and efficacy of 177Lu-DOTATATE in multiple cycles. Methods: Fifty-one consecutive patients with unresectable/metastatic sst 2-positive tumours, divided into two groups, received escalating activities (3.7-5.18 GBq/cycle, group 1; 5.18-7.4 GBq/cycle, group 2) of 177Lu-DOTATATE. Cumulative activities ranged from 3.7 to 29.2 GBq (median 26.4 GBq in median 6 cycles, group 1, 21 patients) and 5.55 to 28.9 GBq (median 25.2 GBq in 4 cycles, group 2, 30 patients), based on dosimetry. Results: No major acute or delayed renal or haematological toxicity occurred (one grade 3 leukopenia and thrombocytopenia). Cumulative renal absorbed doses were 8-37 Gy (9-41 Gy bioeffective doses). A median decrease of creatinine clearance of 21.7% 6 months after PRRT, 23.9% after 1 year and 27.6% after 2 years was observed. Higher losses (>20%) occurred in patients with risk factors for renal toxicity, particularly hypertension and diabetes. Cumulative bone marrow doses were