rhTSH for initial and follow up treatments with 131I in follicular thyroid cancer with distant metastasis.

Objectives There is insufficient data to support the use of recombinant human thyrotropin (rhTSH) for radioactive iodine (RAI) treatment patients with follicular well differentiated thyroid cancer (DTC). Our aim was to assess the safety and efficacy rhTSH-aided treatment in metastatic follicular DTC.

Methods A retrospective analysis was performed of 85 patients at our institution with follicular DTC diagnosed between 1997-2013. Ten patients with proven distant metastasis (bone, lung & liver) were followed for median 46 (27-102) months. rhTSH was used in 9 patients for the initial, and in most of the subsequent RAI treatments. We determined the number of RAI therapies, cumulative 131I doses, serum thyroglobulin (Tg) levels, anatomical imaging and outcomes. This was compared with published data on patients prepared with thyroid hormone withdrawal (THW) protocol.

Results Median age at time of diagnosis was 69.5 (41-84) years. Seven females and 3 males were identified (F:M ratio was 2.4:1.0). Baseline serum Tg levels ranged from 4.5- 5601 ug/L, reflecting heterogeneity of the patient population. Iodine uptake following RAI administration was found in 8 (80%) patients who each received 3-6 treatments with a cumulative dose of 18.4-42.3 GBq (0.5- 1.1 Ci) per patient. Administration of rhTSH promoted satisfactory RAI uptake in all metastatic lesions on post therapy scans. No adverse events were reported among the patients. Serum Tg decreased significantly in 7 patients post therapy, while it increased in one patient despite RAI treatments. At the time of final analysis, 2 patients had persistent disease with continuous reduction in Tg levels, 3 patients had a decline in Tg until 33-44 months, after which they progressed. Two patients died within 31-36 months from their initial assessment, both due to follicular DTC and its complications.

Conclusions The results of rhTSH in metastatic follicular DTC are comparable to published data on THW for similar patient groups. This suggests preparation for RAI therapy with rhTSH is a safe and efficacious alternative to THW in metastatic follicular DTC.