Endocrine Abstracts (2007) 14 P127

Effectiveness of retinoic acid treatment for redifferentiation of thyroid cancer in relation to recovery of radioiodine uptake

Cristián A. Fernández Fernández1, Manel Puig-Domingo1, Francisco Lomeña1, Montserrat Estorch2, Angel L Bittini3, Mónica Marazuela5, Javier Santamaría4, Tomás Martín7, Purificación Martínez de Icaya6, Immaculada Moraga5, María Cuesta7, Ana Mejías8, Manel Porta9, Dídac Mauricio2 & Irene Halperin1

1Hospital Clinic i Provincial de Barcelona, Barcelona, Spain; 2Hospital de Sant Pau, Barcelona, Spain; 3Hospital Gregorio Marañon, Madrid, Spain; 4Hospital de Cruces, Barakaldo, Spain; 5Hospital de la Princesa, Madrid, Spain; 6Hospital de Leganés, Madrid, Spain; 7Hospital Virgen Macarena, Sevilla, Spain; 8Hospital Juan XXIII, Tarragona, Spain; 9Hospital de Vic, Vic, Spain.

Retinoic acid (RA) treatment has been used in the last decade for redifferentiation of metastatic thyroid cancer that have lost radioiodine uptake (RIup) with heterogeneous results.

Aim: To evaluate the improvement of RIup after a course of RA treatment.

Method: Retrospective analysis of 29 patients with radioiodine negative metastatic disease (17 men /12 women; 22 papillary, 4 follicular and 3 oncocytic tumours). RA was given at a dose of 0.66–1.5 mg/kg for 5–12 weeks, followed by a therapeutic 131I dose (3700–7400 MBq). Thyroglobulin levels and CT imaging control after 3 months of RA were performed.

Results: In 44.8% of the patients (14 out of 29 cases, 11 papillary/3 follicular) a positive radioiodine scan was observed; in 7 additional cases (5 papillary, 2 oncocytic) a weak RIup was also apparent (total responders 21/29, 72.4%), and in the remaining 8 the RIup persisted negative (6 papillary, 1 follicular and one oncocytic). No correlation was observed between changes in thyroglobulin levels and recovery of RIup. In 11 RA positive treatments a stabilization of mestastasic growth was observed in 5, while in 6 tumoural mass increased at short term. No major side effects were detected.

Conclusion: A relatively high rate of reinduction of RIup after RA treatment may be possible in advanced stage papillary and follicular thyroid cancer patients, with uncertainty in relation to a potential modification of the natural course of the disease. Further studies, aiming to identify potential responders to RA treatment by a better characterization of the biological nature of these tumours, will be required for an improved indication of RA coadjuvant treatment of thyroid cancer in the future.