131I therapy of thyroid cancer patients

Thyroid cancer is a rare malignancy with wide interethnic and geographic variations. In Germany thyroid carcinoma is the 13th most frequent malignancy (2.7 new cases yearly per 100,000 inhabitants). The overall temporal incidence is increasing slightly in recent years. The most common types of cancer are papillary (60-80%) and follicular cancers (10-20%). The relevant prognostic indicators are tumor stage and distant metastases. The mean survival rates in papillary thyroid cancer usually exceed 90%, whereas in follicular thyroid cancer they amount to approximately 80%. The standard treatment procedure in differentiated papillary and follicular thyroid cancer consists of total thyroidectomy followed by adjuvant ablative therapy with radioiodine. Only in papillary thyroid cancer stage pT1N0M0 lobectomy alone is considered to be appropriate. In patients with locally invasive differentiated thyroid cancers stage pT4 adjuvant percutaneous radiation therapy is a treatment option. Radioiodine therapy has to be performed under the stimulative influence of TSH. Usually TSH suppressive medication with Levothyroxine has to be withdrawn approximately 4 weeks prior to radioiodine therapy. In the future, exogenous stimulation by recombinant TSH may be used instead of thyroid hormone withdrawal. It has been proven by different studies that ablative radioiodine therapy reduces the frequency of recurrences and tumor spread in patients with thyroid cancer significantly. In patients with distant metastases, up to 50% of complete responses may be achieved with radioiodine treatment.