Redifferentiation therapy of differentiated thyroid carcinoma with retinoic acid: basics and first clinical results.

Retinoic acids (RA) regulate growth and differentiation of normal epithelial tissue. They have been employed in anticancer treatment and showed positive effects in hematopoetic and various epithelial tumors. Experimental data with follicular thyroid tumor cells showed strong evidence of induction of differentiated cell function and antiproliferative effects. Based on these data a consecutive series of 10 patients with advanced thyroid carcinoma were treated with 13-cis-retinoic acid (Roaccutan) 1.5 mg/kg body weight for six weeks. Follow-up demonstrated renewed uptake of radioiodine in 4 of 10 patients allowing performance of further radioiodine therapy. Reduction in tumor size due to antiproliferative effects of RA could not yet be verified.