Indications of external beam radiation therapy in non-anaplastic thyroid cancer and impact of innovative radiation techniques

BackgroundThe mainstay of treatment for differentiated thyroid carcinomas is surgery. There is hardly any room for radiation therapy in differentiated thyroid carcinomas. We aimed to update recommendations for RT in the context of histological variants, increased use of radioiodine and new irradiations techniques.Materials and methodsA search of the French and English literature was performed using thyroid carcinoma, radiation therapy, surgery, variants and radioiodine.ResultsPapillary, follicular, Hürthle and medullary carcinomas represent about 80%, 11%, 3% and 4% of all thyroid carcinomas, respectively. Ten-year survival rates for patients with papillary, follicular and Hürthle cell carcinomas are 93%, 85%, and 76%, respectively. The occurrence of criteria such as older age (45 or 60 years-old), massive primary disease, extensive extracapsular spread and macroscopic iodine-negative components inconsistently indicate external beam irradiation (EBRT). The impact of EBRT on poorer-prognosis histological variants is an emerging issue. Noteworthy, the incidence of laryngeal and wound healing complications has been an important limitation to EBRT. However, intensity modulated radiation therapy (IMRT) offers clear dosimetric advantages on tumor coverage and organ sparing such as the larynx, thus reducing late toxicities to less than 5%. Iodine contrast agents should be avoided during 4–6 weeks before radioiodine. PET CT is increasingly used in iodine-negative tumors.ConclusionThere are elective indications for EBRT and IMRT has the potential to improve local control.