Quantitative assessment of radioactivity losses in the administration of therapeutic doses of [177Lu]Lu-DOTA-TATE and [90Y]Y-DOTA-TATE.

Background: Therapeutic radiopharmaceuticals [¹⁷⁷Lu]Lu-DOTA-TATE and [⁹⁰Y]Y-DOTA-TATE are used in peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors. One of the factors determining the efficacy of such therapy is administering the radiopharmaceutical dose to the patients in a way consistent with treatment planning. This paper evaluates the loss of [¹⁷⁷Lu]Lu-DOTA-TATE and [⁹⁰Y]Y-DOTA-TATE and their mixed doses during the administration to the patient either by direct infusion or by gravity method.

Material and methods: The loss of [¹⁷⁷Lu]Lu-DOTA-TATE and [⁹⁰Y]Y-DOTA-TATE, was assessed in tests simulating the administration procedures and during infusion to the patients performed at four clinical centres. One clinical centre used a direct infusion, and three others used a gravity method to administer radiopharmaceuticals to the patient.

Results: In the direct infusion the highest radioactivity loss was 3.88% ± 0.49% (n = 3) and 3.76% ± 0.83% (n = 3) for [¹⁷⁷Lu] Lu-DOTA-TATE infusion with radioactivity of 3.71 GBq ± 0.08 GBq (n = 3) and 1.06 GBq ± 0.08 GBq (n = 3), respectively, and 4.04% ± 0.40% (n = 5) for infusion of [⁹⁰Y]Y-DOTA-TATE dose of 1.98 GBq ± 0.05 GBq (n = 5). In the gravity method administration of [¹⁷⁷Lu]Lu-DOTA-TATE generated losses of up to 1.31% ± 0.46% (n = 16) for a dose of 7.45 GBq ± 0.06 GBq (n = 16) and 2.93% ± 1.64% (n = 8) for a dose of 3.78 GBq ± 0.05 GBq (n = 8). However, the infusion of the lowest doses of 0.95 GBq ± 0.01 GBq (n = 4) [¹⁷⁷Lu]Lu-DOTA-TATE and 1.96 GBq ± 0.03 GBq (n = 8) [⁹⁰Y]Y-DOTA-TATE resulted in higher loss of radiopharmaceuticals up to 6.00% ± 0.97% (n = 4) and 4.00% ± 1.57% (n = 8), respectively.

Conclusions: Both investigated methods of radiopharmaceutical administration are associated with the loss of the radioactivity of radiopharmaceutical.