Role of external beam radiation therapy in the treatment of thyroid cancer

Results of retrospective studies on differentiated thyroid cancer suggest that patients with true invasion of adjacent organs (stage T4 in TNM 2002) benefit from external beam radiotherapy regarding locoregional control and in an R2 situation even regarding disease-specific survival. The German MSDS trial could only partly clarify the role of external beam radiotherapy in differentiated thyroid cancer with extracapsular extension. International guidelines currently recognize a small high-risk group which benefits from external beam radiotherapy after optimal surgery and radioiodine treatment. In undifferentiated thyroid cancer external-beam radiotherapy is usually indicated even in the presence of distant metastases. It should be administered with at least 40 Gy and achieves locoregional control in 60-80% of cases. Patients without distant metastases and at least macroscopically complete resection might benefit from trimodal treatment.