Evaluation of Low-Dose Radioiodine Ablation Therapy in Postsurgical Thyroid Cancer Patients

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Abstract
Nineteen patients with differentiated thyroid carcinoma were given low dose (30 mCi), radioiodine therapy for the ablation of residual thyroid tissue following total thyroidectomy. Using 5- to 10-mCi diagnostic I-131 scans, ablation was achieved in two of 19 patients following the first low dose and three of 12 patients following the second low-dose therapy. The ablation response was 53% (ten of 19) following one large dose (100 mCi) in another concurrent group of 19 patients. The ablation response following the first low dose when compared with the first high-dose therapy was significantly lower (P = 0.015). The combined ablation response following first and second low doses (five of 14) when compared to a single large dose was not significantly different (P = 0.534). The use of low-dose-I-131 therapy, although not as effective as large dose therapy, may be warranted in patients resistant to entering the hospital for therapy. However, ablation as defined by a five- to ten-mCi I-131 scan can be expected to occur in only one third of the patients after two attempts at ablation, while a single 100-mCi regimen can be successful in achieving ablation in over one half of the patients after the first attempt.