Title : Previous external beam radiation treatment exposure does not confer worse outcome for patients with differentiated thyroid cancer

BACKGROUND Radiation exposure, especially in childhood, is known to increase the risk for the development of thyroid cancer. However, the prognosis of patients with thyroid cancer with a history of radiation treatment exposure remains unclear. METHODS One hundred and sixteen patients with a previous history of radiotherapy in the head and neck region were identified from an institutional database of 3664 patients with differentiated thyroid cancer treated between 1986 and 2010. Using the Kaplan-Meier method, disease-specific survival and recurrence-free survival were compared between patients with (RT; n = 116) and without (No RT; n = 3509) a prior history of radiation exposure. RESULTS The median ages of the RT and No RT cohorts were 52 and 47 years. The median follow-up for both groups was 54 months. Patients who had a prior history of radiation treatment exposure were more likely to be male (38.8% vs. 26.9%; p = 0.005) and older than 45 years of age (67.2% vs. 53.9%; p = 0.005). Other patient, tumor, and treatment characteristics were similar between the groups. There was no difference in the five-year disease-specific survival of the RT and No RT patients (97.4% vs. 98.7%; p = 0.798). The five-year recurrence-free survival was also similar between the RT and No RT patients (97.8% vs. 94.9%; p = 0.371). CONCLUSION The findings suggest that differentiated thyroid cancer patients with a history of prior radiation treatment exposure have similar outcomes to those with no history of head and neck radiation exposure.