CONVERSION OF NON-IODINE-CONCENTRATING DIFFERENTIATED THYROID-CARCINOMA METASTASES INTO IODINE-CONCENTRATING FOCI AFTER ANTICANCER CHEMOTHERAPY

We present the unusual case of a 29-year-old man diagnosed in 1975 wit h papillary carcinoma of the thyroid metastatic to regional lymph node s. The patient underwent surgical resection, postoperative iodine-131 (I-131) radioablation and levothyroxine suppression. He was subsequent ly lost to follow-up. In 1991, he presented with extensive metastatic disease that was not demonstrable on whole-body I-131 imaging, but was seen on computerized tomography and whole-body thallium chloride scan ning. The patient was treated with cisplatin (PlatinolTM) and doxorubi cin (AdriamycinTM). Repeat I-131 imaging after three cycles of chemoth erapy showed significant I-131 uptake in previously non-iodine-concent rating lesions. The patient was subsequently treated with 200 mCi I-13 1. We postulate this patient's non-iodine-concentrating thyroid cancer may have become functional by either a differentiating effect of chem otherapy on the tumor cells, or perhaps a selective cytotoxicity again st nonfunctional, less differentiated papillary thyroid cancer cells, or both. This would allow more functional differentiated cells to over grow and become the predominant cell type in the lesions. Chemotherapy may be beneficial in patients with advanced non-iodine-concentrating differentiated thyroid carcinoma by inducing radioiodine uptake and al lowing subsequent radioiodine therapy. The possible mechanisms of indu ction of iodine uptake by chemotherapy are discussed.