Predictive factors for thyroid complications after radiation therapy-data from a cohort of cancer patients closely followed since they were irradiated.

Introduction: Cancer survivors are at an increased risk of adverse outcomes, including thyroid neoplasms, given the high radiosensitivity of this gland. The aim of this study is to assess the incidence and timeframe of thyroid complications in cancer patients, followed systematically since their radiation therapy, and to identify risk factors for the development of hypothyroidism and thyroid cancer.

Methods: We performed a retrospective study, including 282 subjects, who received neck, craniospinal, or total body irradiation (TBI). Patients were grouped into four primary diagnostic clusters: leukaemia, Hodgkin's disease, central nervous system, and head and neck tumours.

Results: Hypothyroidism was observed in 56.7% of patients, on average 6.8 ± 5.9 years after the treatment. Neck and craniospinal irradiation presented a 3.5-fold increased risk for the development of hypothyroidism compared to TBI. Papillary thyroid cancer was diagnosed in 8.5% of the patients, on average, 18.5 ± 4.9 years after radiotherapy (RT). Female gender, younger age, and lower irradiation doses were independently associated with thyroid cancer development.

Conclusion: Our study provides useful information about the risk of hypothyroidism and thyroid cancer after RT, as it was performed in a cohort of patients closely followed since the oncological therapies, and, thus, may give new insights into the follow-up management of these patients.