Receptor-mediated radiotherapy with ⁹⁰Y-DOTA-_DPhe¹-Tyr³-octreotide: The experience of the european institute of oncology group1

High concentrations of subtype 2 somatostatin tumor receptors (sst₂) are expressed in numerous tumors, enabling primary and metastatic masses to be localized by scintigraphy after injecting ¹¹¹In-labeled somatostatin analogue octreotide. In addition to neuroendocrine tumors, somatostatin receptors have been identified on cancers of the central nervous system, breast, lung, and lymphatic tissue, and the use of radionuclide-labeled somatostatin analogues appeared promising for therapy as well as for diagnosis of such malignancies. The somatostatin analogue [DOTA-_DPhe¹-Tyr³] octreotide (DOTATOC) possesses favorable characteristics for its potential therapeutic use in that it shows high affinity for sst₂, moderately high affinity for sst₅, and intermediate affinity for sst₃, high hydrophilicity, stable and facile labeling with ¹¹¹In and ⁹⁰Y. We began to investigate the potential therapeutic applications of ⁹⁰Y DOTATOC in 1997 by performing a thorough dosimetric study in 18 patients who were administered ¹¹In DOTATOC to estimate the absorbed doses during ⁹⁰Y-DOTATOC therapy. Then, we moved on and treated an overall number of 256 patients, mostly recruited in 2 distinct protocols with and without the administration of kidney protecting agents, with ⁹⁰Y DOTATOC. No major acute reactions were observed up to the activity of 5.55 GBq per cycle. The MTD per cycle was defined as 5.18 GBq. Objective therapeutic responses were documented in more than 20% of patients in terms of partial and complete responses. The present article reports in detalis our clinical experience (still ongoing) and outcomes with the use of ⁹⁰Y DOTATOC.

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