L-T3 Preparation for I131 Whole Body Scintigraphy: A Randomized Controlled Trial
Patients with well differentiated thyroid cancer (DTC) need whole-body scintigraphy (WBS)
and thyroglobulin (Tg) measurement in order to detect recurrence. Classically, withdrawal
from levothyroxine (L-T4) during 4-6 weeks is needed for TSH elevation (> 30mUI/L), to allow
iodine uptake and Tg production. As a result, patients become hypothyroid with impaired
quality of life and a potential for tumour flare-up. Recombinant hTSH before WBS prevents
hypothyroidism but is not yet approved for radioiodine treatment and is an expensive
therapy. L-T3 substitution during the first 2-3 weeks of withdrawal is an alternative used
empirically to prepare patients; however, no data exists to prove its benefit upon reducing
Objectives: 1) To compare the hypothyroid state in patients prepared either by placebo or
L-T3 following L-T4 withdrawal. 2) To evaluate the time needed for TSH elevation (> 30
mUI/L) on placebo vs. L-T3.
Method: At the time of L-T4 withdrawal or after thyroidectomy, patients with DTC awaiting
WBS or radioiodine treatment were randomized in two groups (double-blind): L-T3 (50 mg qd)
or an identical placebo for 3 weeks, after which treatment was stopped for 2 weeks. A
validated questionnaire of signs and symptoms of hypothyroidism (Billewicz’s scale) was
administered every 2 weeks until the WBS. TSH, fT4 and fT3 were measured weekly.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double-Blind, Primary Purpose: Treatment
Evaluation of the hypothyroid status by the Billewicz questionnaire.
Rébecca Leboeuf, MD
Universitaire de Sherbrooke
Canada: Health Canada