Radiation exposure, especially in childhood, is known to increase the risk for development of thyroid cancer. However, the prognosis of patients with thyroid cancer secondary to radiation exposure remains less definitive.
One hundred and sixteen patients with a previous history of head and neck radiotherapy were identified from an institutional database of 3664 patients with differentiated thyroid cancer treated between 1986 and 2010. Thirty-nine patients with a self reported history of Chernobyl exposure was excluded from analysis. Disease Specific Survival (DSS) and Recurrence Free Survival (RFS) were compared between patients with (RT) and without a prior history of radiation exposure (NoRT), using the Kaplan Meier method.
The median ages of the RT and NoRT cohorts were 52 and 47 years old. The median follow ups for both groups were 54 months with a range of 1-313 months and 13-332 months, respectively. Figure 1 demonstrates the indication for radiotherapy. Patients who had a prior history of radiation exposure were more likely to be male (38.8% vs 26.9%, p=0.005) and over 45 years of age (67.2% vs. 53.9%, p=0.005). Other patient, tumor and treatment characteristics were similar between the patients with and without prior radiotherapy (Table 1). No difference was detected in the 5 year DSS of patients with and without radiation exposure (97.4% vs. 98.7%, p=0.798). The 5 year RFS was also similar between the radiation exposed and non exposed patients (97.8% vs. 94.9%, p=0.371).
Our findings suggest that differentiated thyroid cancer patients with a history of prior radiation exposure have similar outcomes to those with no history of head and neck radiation exposure.