Incidence of thyroid dysfunction post radiotherapy in head and neck cancer

Background: Globally, head and neck cancer rank sixth in terms of incidence with squamous cell carcinoma being the most common. In case of early-staged cancer (T1 or T2), it is treated with a single modality of treatment, such as radiation therapy or surgery. In locally advanced head and neck cancer, it is treated with radiotherapy with or without chemotherapy. Primary hypothyroidism is indicated to be in between 11-53%. Aim is to estimate the incidence of thyroid dysfunction post radiotherapy in head and neck cancer. Methods: This is a prospective and observational study done in a tertiary care centre over a period of 1 year in 66 patients. Written and informed consent was taken, data was collected in a predesigned questionnaire and baseline blood tests was done prior, 3rd and 6th month post radiotherapy. Results: The incidence of hypothyroidism in our study was 15.15% with maximum incidence was found in Ca larynx (29.16%) followed by Ca hypopharynx (22.22%). 15.5% hypothyroid patients were treated with concurrent radiotherapy whereas 12.5% were not. Conclusions: Hypothyroidism incidence increases with time, where majority develop after 6 months post-radiotherapy. Age, sex and concurrent chemotherapy were not identified as relevant risk factors in our study. Smaller sample size, shorter time period and single centre based were the limitations of the study.