Does radioiodine therapy have an equal effect on substernal and cervical goiter volumes? Evaluation by magnetic resonance imaging.

Most often thyroidectomy is recommended in patients with large goiters. However, high-dose (131)I therapy may be used in case of contraindications to surgery. Large goiters are often partially located in the mediastinum. The aim of this study was to evaluate the impact of (131)I therapy on the cervical and the substernal goiter volume, separately. Fourteen patients (median age, 69 years; range, 52-86 years) with a large multinodular goiter (three hyperthyroid) and with a substernal extension greater than 15 mL were included. T1-weighted magnetic resonance (MR) estimates of the thyroid volume in the cervical and substernal compartments were obtained before and 1 year after high-dose (131)I therapy. The total goiter volumes ranged from 182 to 685 mL. The median substernal volume was 66 mL (fraction of total volume, 17.6%; range, 8.0%-78.9%). One year after treatment, the median substernal goiter volume was reduced by 29.2% (range, -6.1%-59.4%, mean: 26.1% +/- 6.0%), and the cervical goiter volume by 30.3% (range, 6.0%-75.4%, mean, 35.6 +/- 5.6%) compared to baseline values; p = 0.25 for difference in a regional effect. The volume reduction was unrelated to initial substernal goiter size. Likewise, deterioration of the inspiratory capacity did not correlate with the magnitude of the substernal goiter extension. In conclusion, high-dose (131)I therapy seems as effective in reducing the substernal as the cervical goiter volume. However, because the overall effect is modest, this therapy should primarily be considered for the patient with a high surgical risk.