1 Department of radiology & nuclear medicine, Noguchi Thyroid Clinc & Hospital Foundation, Beppu, Oita, Japan
Background: It is now known that the clinical behavior and management of poorly differentiated thyroid carcinoma (PDTC) are very different from differentiated thyroid carcinoma (DTC). Despite the difference, therapy for distant metastasis are limited. In Japan, the first choice for distant metastasis will be radioiodine therapy, even for PDTC.
Methods: From Jan.2007 to Dec.2016, 178 cases undergone the 1st radioiodine therapy for distant metastasis. Among the 178 cases there were 18 cases had been diagnosed as PDTC from the primary lesions (10.1%). In these 18 cases, one had residual tumor, one had chemotherapy for rectal cancer and one had only 4 month of observation, so these 3cases were excluded. The outcome of radioiodine therapy were retrospectively evaluated by using 15 cases. 6 male, 9 female with an average age of 65.1 (19-85). The observation period was 8-117 month with a mean of 50.1 month.
Results: 9 cases were avid for radioiodine and 3 cases were stable while observation. However 3 had progression and 3 died due to thyroid cancer. The remaining 6 cases did not have avidity and 5 had progression, 1 died due to the disease. The avid group had a mean observation period of 52.0 month (19-113) while the non-avid group was 45.2 month (8-117).
The radioiodine therapy for distant metastasis of PDTC did not have the benefit as we see in DTC. But even though, it is likely that with radioiodine avid lesions, radioiodine therapy could be profitable even with distant metastasis of PDTCs.