[Use of 13-cis retinoic acid for treatment of advanced differentiated thyroid cancer]

Retinoids, a large group of compounds structurally related to vitamin A, are able to induce redifferentiation of thyroid cancer cells. The aim of the study is to present our early results of retinoids redifferentiation therapy of thyroid cancer patients. In 15 patients with advanced thyroid cancer, whose cancer foci did not concentrate radioiodine, 13-cis retinoic acid (Roaccutan) was given for 6 weeks before radioiodine treatment. Radioiodine therapy was performed under exogenous TSH stimulation (Thyrogen). Three patients were treated twice. The planned retinoid dose was delivered to 11 patients. In the other four patients the reduction of retinoids dose was necessary due to severe side effects. In post-therapeutic scintigraphy radioiodine uptake was visible in two out of seven patients (29%) with lung metastases, in 5 out of 9 (56%) with locoregional disease and in two with bone metastases. On the whole, in 50% of patients reinduction of radioiodine uptake was visible, however, in most patients only a very discrete one. Thyroglobulin concentration before and after retinoids therapy did not differ significantly.

In a subgroup of patients 13-cis retinoic acid can induce radioiodine uptake, however, prospective studies in larger groups of patients are necessary to prove its clinical application.