(177)Lu-DOTATATE was well tolerated up to 29 GBq cumulative activity (up to 7.4 GBq/cycle). The maximum tolerated dose/cycle was not reached. However, considering the individual bone marrow function and the presence of risk factors for kidney toxicity, it seems safer to divide cumulative activities into lower activity cycles.

The aim of this study was to determine the maximum tolerated dose of (90)Y-DOTATOC per cycle administered in association with amino acid solution as kidney protection in patients with somatostatin receptor-positive tumours. Forty patients in eight groups received two cycles of (90)Y-DOTATOC, with activity increased by 0.37 GBq per group, starting at 2.96 and terminating at 5.55 GBq. All patients received lysine +/- arginine infusion immediately before and after therapy. Forty-eight percent developed acute grade I-II gastrointestinal toxicity (nausea and vomiting) after amino acid infusion whereas no acute adverse reactions occurred after (90)Y-DOTATOC injection up to 5.55 GBq/cycle. Grade III haematological toxicity occurred in three of seven (43%) patients receiving 5.18 GBq, which was defined as the maximum tolerable activity per cycle. Objective therapeutic responses occurred. Five GBq per cycle is the recommended dosage of (90)Y-DOTATOC when amino acids are given to protect the kidneys. Although no patients developed acute kidney toxicity, delayed kidney toxicity remains a major concern, limiting the cumulative dose to ~25 Gy. The way forward with this treatment would seem to be to identify more effective renal protective agents, in order to be able to increase the cumulative injectable activity and hence tumour dose.

Somatostatin receptors are over-expressed in many tumours, mainly of neuroendocrine origin, thus enabling treatment with somatostatin analogues. Almost a decade of clinical experience of receptor radionuclide therapy with the analogue (90)Y-[DOTA](0)-Tyr(3)-octreotide [(90)Y-DOTATOC] has now been obtained at a few centres of excellence. This review reports on the present state of the art of receptor radionuclide therapy and discusses new perspectives.

While the incidence of brain tumours seems to be increasing, median survival in patients with glioblastoma remains less than 1 year, despite improved diagnostic imaging and neurosurgical techniques, and innovations in treatment. We have developed an avidin-biotin pre-targeting approach for delivering therapeutic radionuclides to gliomas, using anti-tenascin monoclonal antibodies, which seems potentially effective for treating these tumours. We treated 48 eligible patients with histologically confirmed grade III or IV glioma and documented residual disease or recurrence after conventional treatment. Three-step radionuclide therapy was performed by intravenous administration of 35 mg/m2 of biotinylated anti-tenascin monoclonal antibody (1st step), followed 36 h later by 30 mg of avidin and 50 mg of streptavidin (2nd step), and 18-24 h later by 1-2 mg of yttrium-90-labelled biotin (3rd step). 90Y doses of 2.22-2.96 GBq/m2 were administered; maximum tolerated dose (MTD) was determined at 2.96 GBq/m2. Tumour mass reduction (>25%-100%), documented by computed tomography or magnetic resonance imaging, occurred in 12/48 patients (25%), with 8/48 having a duration of response of at least 12 months. At present, 12 patients are still in remission, comprising four with a complete response, two with a parital response, two with a minor response and four with stable disease. Median survival from 90Y treatment is 11 months for grade IV glioblastoma and 19 months for grade III anaplastic gliomas. Avidin-biotin based three-step radionuclide therapy is well tolerated at the dose of 2.2 GBq/m2, allowing the injection of 90Y-biotin without bone marrow transplantation. This new approach interferes with the progression of high-grade glioma and may produce tumour regression in patients no longer responsive to other therapies.