PSMA was obtained from ABX GmbH (Radeberg, Germany). To begin, 1 mg DOTA-PSMA was dissolved in 1 ml 0.05 M HCl. Then, 88.50 ± 9.21 μg DOTA-PSMA per 10 μg Lu was added to 1 ml 0.05 M HCl solution containing 42 mg gentisinic acid and 210 mg sodium ascorbate. This mixture was added to carrier-added 177LuCl3, obtained from IDB Holland, and heated for 30 min at 95 °C. Quality control was performed by spotting 1 μl aliquots on TLC (SilicaGel 60, Merck, Darmstadt, Germany) with 0.1 M citric buffer or ITLC-SG plates (ITLC-SG, Varian, Lake Forest, CA, USA) and with 1 M NH4OAc/MeOH (1:1) as solvent. Analysis was performed using a flat-bed scanner (Rita Star, Raytest-Isotopenmessgeräte GmbH, Straubenhardt, Germany). Radiochemical purity was determined by radio HPLC, which was performed using a gradient system. The gradient elution system utilised mobile phase A (deionised H2O containing 0.1 % TFA) and mobile phase B (100 % acetonitrile) and a flow rate of 1.0 ml/min. Starting with 100 % A/0 % B, the gradient was increased to 100 % B over 30 min and then returned to the initial gradient conditions within 5 min. The retention time of free 177Lu was Rt = 2.5 min, whereas for Lu-PSMA it was 13.3 min.
The labelling yield always exceeded 95 % (98.85 ± 1.29 %); therefore, no purification was performed. The radiochemical purity was higher than 98 %. The specific activity of Lu-PSMA was 89.73 ± 13.61 MBq/μg.
The therapy solution was administered by slow intravenous injection over 1 min followed by 1000 ml of NaCl or Ringer. In order to reduce therapy-induced damage to the salivary glands, the patients received ice packs over the parotid and submandibular glands from 30 min prior to and up to 4 h after administration of the Lu-PSMA. All patients were discharged 48 h after therapy according to the rules of the Federal Office for Radiation Protection in Germany (BfS).
The labelling yield always exceeded 95 % (98.85 ± 1.29 %); therefore, no purification was performed. The radiochemical purity was higher than 98 %. The specific activity of Lu-PSMA was 89.73 ± 13.61 MBq/μg.
The therapy solution was administered by slow intravenous injection over 1 min followed by 1000 ml of NaCl or Ringer. In order to reduce therapy-induced damage to the salivary glands, the patients received ice packs over the parotid and submandibular glands from 30 min prior to and up to 4 h after administration of the Lu-PSMA. All patients were discharged 48 h after therapy according to the rules of the Federal Office for Radiation Protection in Germany (BfS).
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