Evaluation of prophylactic postoperative 131I therapy for extended differentiated carcinoma of the thyroid gland.

Varying survival rates have been reported for differentiated carcinoma of the thyroid gland. The rate, however, does progressively decrease over a longer period of time than the usually reported five-year survival rates. Significant local invasion outside the thyroid capsule and of blood vessels yields a poorer prognosis, and mortality is largely attributed to distant metastasis. To improve the long-term survival rate, 1) sharp dissection with ample safety margin including resection of the neighboring organs, 2) reconstruction of the sacrificed organs, if possible, and 3) postoperative prophylactic radioiodine therapy, were adopted for invasive well-differentiated carcinoma for a period of 10 years. Of the 191 well-differentiated carcinomas operated on, in a series of 486 consecutive thyroid operations, 33 patients underwent this prophylactic radioactive iodine therapy (dose amount up to 300 mCi) following ablative surgery including, in several patients, mediastinal dissection. Periodical whole body survey by sodium iodide 131I showing no signs of recurrence up to five years except in three patients indicating two suspected lung metastasis and one death from bone metastasis, demonstrated that this is a promising method for the treatment of invasive well-differentiated carcinoma of the thyroid gland, although further long-term analysis is required.