Recombinant human thyrotropin for the diagnosis and treatment of a highly functional metastatic struma ovarii

The optimal treatment of metastatic thyroid cancer that produces high amoun ts of thyroid hormone has not been well defined. A 46-yr-old woman presente d with a follicular thyroid carcinoma arising from a struma ovarii with hep atic metastases. After the removal of both the struma and the thyroid gland , the liver metastases showed evidence of a high degree of hormonogenesis. Brain, chest, abdomen, and bone imaging was negative for additional metasta ses. Because iodine uptake by most thyroid carcinomas is quite low in the a bsence of high levels of ambient TSH, we used recombinant human TSH (rhTSH) (Thyrogen) to achieve a concentration of I-131 activity in the tumor high enough for a significant cytotoxic effect. After rhTSH administration (0.9 mg im daily for 2 consecutive days), a I-131 diagnostic whole body scan con firmed the existence of 17 discrete hepatic fool of I-131 uptake. To calcul ate the amount of I-131 that would deliver an absorbed radiation dose that would be optimally cytotoxic to the metastases (>8000 rad/lesion) and not. to the normal liver, we performed lesion dosimetry. Analysis of dosimetric data showed that 15 of 17 lesions would receive an adequate radiation dose following the administration of 65 mCi of I-131. Additionally, we performed whole body dosimetry to assure that this dose would not cause bone marrow toxicity. The patient was reevaluated 6 months after therapy; the liver met astases showed significant, but partial, response. In conclusion, we used t he combination of rhTSH with lesional and whole body dosimetry for the trea tment of highly functional metastases from follicular thyroid carcinoma ari sing within a struma ovarii. This strategy can be applied to determine a sa fe and effective dose of I-131 for the treatment of any thyroid cancer meta stases that produce enough TH to preclude stimulation of endogenous pituita ry TSH secretion.