Endocrine Abstracts (2010) 22 P448

Conditions and implications of rhTSH application for ablation in treatment of Differentiated thyroid cancer

Pavla Sykorova, Marketa Mackova & Petr Vlcek

Department of Nuclear Medicine and Endocrinology, Charles University in Prague, 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic.

A basic tool of the thyroidal cancer treatment is the total thyroidectomy. Immediately after the thyroidectomy, the patients receive a thyroxin. In the case of positive histology after lobectomy, we first indicate the total thyroidectomy. If the tumor is larger than 1 cm or if is a multifocal one, we indicate the ablation of the remnant with I131.

Usually, the differentiated thyroid cancer is non-aggressive and we proceed with a standard way of the ablation – after thyroxin 4 week withdrawal. We always use the diagnostics scan with I131 74 MBq. Depending on the results, we administrate 4 different dosages in liquid: (1) 2900 MBq for negligible remnant, (2) 3700 MBq for average remnant 3–7% accumulation in 24 h, (3) 5500 MBq for 7–10%, and (4) 7500 MBq in the presences of distant metastasis.

Patients with more aggressive form of the cancer that is invasive into the thyroid capsule or in a presence of a lymph node metastasis are in the risk of the tumor growing in the remnant. If the result of diagnostic scan after 4 week thyroxin withdrawal is larger than 10% of the 24 h accumulation then we cannot decide whether it is a failure of the surgery or the growing up tumor. In these cases, we indicate reoperation and afterwards we use rhTSH (Thyrogen) instead of the thyroxin withdrawal. This situation appeared in 7 cases in the last year.

Economic aspects do not allow us to use rhTSH for all ablations which would make the treatment easier for patients. But we can choose the patients with a high risk of the growing tumor. This allows us to prevent them from stimulating influence of the TSH that would otherwise be used over long time (typically 4 weeks).

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