Thyroid Research Thyroid Research Archive Thyroid Cancer

Radioactive iodine therapy may reduce the risk of recurrence of papillary and follicular carcinoma after surgery

(November 2004)

The background of the study. Most patients with papillary or follicular thyroid carcinoma are treated by thyroidectomy. Radioiodine (I-131) is then given to destroy any remaining normal thyroid tissue (remnant ablation). This analysis was undertaken to determine if remnant ablation reduces the mortality or recurrence rate in patients with thyroid carcinoma.

How the study was done. The literature was searched to identify studies of patients who had papillary or follicular thyroid carcinoma, underwent bilateral thyroidectomy, and were treated with I-131 within 1 year after surgery; who were followed for at least 5 years; and for whom 10-year data on outcome were reported. Twenty-three studies met the inclusion criteria.

The results of the study. Seven studies reported mortality data. One study of 1510 patients found a significant benefit of I-131 therapy, after adjustment for age, sex, extent of surgery, and tumor characteristics. There was no benefit of I-131 therapy in six other studies, in which the 10-year cancer mortality rates varied from 1.3 to 15 percent. In 20 studies not adjusted statistically for other variables, the 10-year mortality rates varied from 0 to 23 percent among I-131-treated patients and 0 to 25 percent among those not treated.

I-131 therapy was associated with a lower risk of local or regional recurrence in three studies (relative risks, 0.05, 0.3, and 0.4). The pooled 10-year local and regional recurrence rates were lower in I-131-treated patients with either papillary or follicular carcinoma than in those not treated. I-131 therapy also was associated with a lower risk of distant metastases in the largest study, of 1510 patients. The pooled 10-year rate of distant metastases was lower in the I-131-treated patients with either papillary or follicular carcinoma than in those not treated.

The conclusions of the study. In patients with papillary or follicular carcinoma of the thyroid, I-131 therapy may reduce the frequency of local recurrence and distant metastases, but has little effect on mortality.

The original article. Sawka AM, Thephamongkhol K, Brouwers M, Thabane L, Browman G, Gerstein HC. A systematic review and metaanalysis of the effectiveness of radioactive iodine remnant ablation for well-differentiated thyroid cancer. J Clin Endocrinol Metab 2004;89:3668-76.