Utility of outpatient fractionated radioiodine therapy for Graves disease involving a large goiter measuring more than 100 mL in volume.

Contrary to large multinodular goiters, reports on I radioiodine therapy (RIT) for Graves disease (GD) involving a large goiter are scarce. We retrospectively reviewed a total of 71 consecutive patients (25 males, 46 females) with GD involving a large goiter (>100 mL) who had received RIT in our clinic. Patients with a history of thyroid surgery or with large thyroid nodules and those who had dropped out less than one year after the initial RIT session were excluded. A fixed I activity of 481 MBq was administered in most cases. RIT was repeated at intervals of 1-47 months, typically 3-6 months. The follow-up duration after the initial RIT session was 13-233 (median: 81) months. The thyroid volume was estimated using ultrasound. The number of I doses were 1 dose in 13 patients, 2 doses in 29, 3 doses in 17, 4 doses in 5, 5 doses in 5, 6 doses in 1, and 8 doses in 1. Sixty-six patients had remission from overt hyperthyroidism after RIT: overt hypothyroidism in 45 patients, subclinical hypothyroidism or euthyroidism in 13, and subclinical hyperthyroidism in 8. Their thyroid volume decreased from 101-481 (median: 126) mL to 1.4-37 (8.2) mL. Three patients still had overt hyperthyroidism under treatment with methimazole after one to three doses, and two dropped out less than six months after the third or sixth dose. Even in GD patients with a large goiter (>100 mL), repeated RIT with an activity of 481 MBq could sufficiently shrink goiters and remit overt hyperthyroidism.