This analysis was performed to determine the effect of initial therapy on the outcomes of thyroid cancer patients. The study setting was a prospectively followed multi-institutional registry. Patients were stratified as low risk (stages I and II) or high risk (stages III and IV). Treatments employed included near-total thyroidectomy, administration of radioactive iodine, and thyroid hormone suppression therapy. Outcome measures were overall survival, disease-specific survival, and disease-free survival. Near-total thyroidectomy, radioactive iodine, and aggressive thyroid hormone suppression therapy were each independently associated with longer overall survival in high-risk patients. Near-total thyroidectomy followed by radioactive iodine therapy, and moderate thyroid hormone suppression therapy, both predicted improved overall survival in stage II patients. No treatment modality, including lack of radioactive iodine, was associated with altered survival in stage I patients. Based on our overall survival data, we confirm that near-total thyroidectomy is indicated in high-risk patients. We also conclude that radioactive iodine therapy is beneficial for stage II, III, and IV patients. Importantly, we show for the first time that superior outcomes are associated with aggressive thyroid hormone suppression therapy in high-risk patients, but are achieved with modest suppression in stage II patients. We were unable to show any impact, positive or negative, of specific therapies in stage I patients.

We used a combination of radioiodine scanning and quantitative radiation dosimetry to evaluate responses to therapeutic irradiation with 131I in 76 patients with thyroid adenocarcinoma. Fifty patients received 131I treatment for ablation of residual thyroid tissue after surgical thyroidectomy, and 26 had 131I treatment for metastatic thyroid cancer. Successful ablation was observed in patients receiving higher radiation doses to the thyroid--about 4.4 times those in patients whose lesions were not ablated--largely because of a longer effective half-life of 131I in residual thyroid tissue in the patients with ablated lesions. Patients with metastases that persisted after 131I therapy tended to have more advanced disease and received significantly lower radiation doses per millicurie of administered 131I than did persons whose lesions responded to treatment. Initial 131I treatment resulting in radiation doses of at least 30,000 rad to thyroid remnants and 8000 rad to metastases was associated with a significant increase in the rate of response to therapy.

Thyrotropin stimulates radioiodine uptake for scanning in patients with thyroid cancer, but the sensitivity of scanning after the administration of thyrotropin is less than that after the withdrawal of thyroid hormone. Thyrotropin scanning is associated with fewer symptoms and dysphoric mood states.

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