PRESCRIBING (131)IODINE BASED ON NECK UPTAKE PRODUCES EFFECTIVE THYROID-ABLATION AND REDUCED HOSPITAL STAY

Purpose: The aim of this study was to determine if thyroid cancer pati ents with low percentage neck uptake of iodine on postoperative thyroi d scans can be treated with lower doses of (131)Iodine while maintaini ng a high ablation rate.Materials and methods: We reviewed the records of 58 patients with differentiated thyroid cancer treated with I-131 at the Princess Margaret Hospital. The activity of I-131 was prescribe d based on the 48 h percentage neck uptake in postoperative thyroid sc ans. Patients with less than or equal to 2% uptake received 1.07 GBq, patients with 2.1-4% uptake received 1.85 GBq, patients with 4.1-6% up take received 2.80 GBq, patients with 6.1-8% uptake received 3.70 GBq and patients with >8% uptake received 4.60 GBq. When the scan suggeste d cervical lymph node metastases or residual tumor, 7.40 GBq was presc ribed. Follow-up scans were performed at least 5 months after I-131 th erapy. Successful ablation was defined as the absence of visible uptak e in the neck above background. Results: Forty-nine patients were incl uded in this analysis. The ablation rate according to the prescribed a ctivity was as follows: 1.07 GBq, 16/20 (80%); 1.85 GBq, 4/5 (80%); 2. 80 GBq, 1/1 (100%); 3.70 GBq, 0/1 (0%); 4.60 GBq, 7/8 (88%); 7.40 GBq, 13/14 (93%). The ablation rate for all patients treated on the protoc ol was 41/49 (84%, 95% CI 70-93%). For the group treated for remnant a blation, the overall ablation rate was 28/35 (80%, 95% CI 63-92%). Twe nty-two (38%) of the 58 eligible patients received 1.07 GBq as outpati ents. This saved 38 hospitalization days compared to a policy of treat ing all patients requiring remnant ablation with 3.70 GBq. Conclusions : We conclude that patients with less iodine uptake in postoperative t hyroid scans can receive lower activities of I-131, allowing a signifi cant proportion of patients to be treated on an outpatient basis while maintaining a high ablation rate. (C) 1998 Elsevier Science Ireland L td. All rights reserved.