A prospective study of radiation-induced hypothyroidism in head and neck cancer patients

Background: Head and neck cancers are one of the most common cancers worldwide. Radiotherapy is the only curative treatment, besides surgery. The most common clinical late effect of thyroid gland irradiation in patients exposed to therapeutic doses to the neck is hypothyroidism, and hypothyroidism causes morbidity and mortality if untreated. There is not enough data about post-radiotherapy hypothyroidism in head and neck cancer patients in eastern India. Objectives: The purpose of our study is to identify the incidence of hypothyroidism following radiotherapy in head and neck cancer patients in eastern India and to assess the time period for the development of hypothyroidism for early treatment to reduce hypothyroid related morbidity and mortality. Materials and Methods: The study was done in 107 histopathologically proved head and neck cancer patients between June 2013 and May 2016. Patients were treated with Cobalt 60 Teletherapy machine with conventional fractionation. 31 (28.9%) patients received concurrent chemoradiation with weekly Cisplatin, 50 (46.7%) patients received radiation alone, and 26 (24.3%) patients received neo-adjuvant chemotherapy with injection Paclitaxel and injection Carboplatin followed by radiation. Results: Male patients were 80 (74.8%) and 27 (25.2 %) were female patients, and the age groups were 42–70 years, and the median age was 52 years. Primary tumor in the majority of the patients was carcinoma larynx 51 (47.6%). At 36 months of follow-up 13 (25%), patients were to have subclinical hypothyroidism, 9 (17.3%) patients were to have clinical hypothyroidism, and percentage of hypothyroidism was 42.3%. The first occurrence of hypothyroidism was seen over a follow-up period of 6 months in our study. Conclusion: It is recommended that serum thyroid stimulating hormone and free T4 have been estimated before initiation of radiotherapy and post radiotherapy at regular interval 6–12 months and carried out lifelong and physicians should not neglect to evaluate thyroid function of post-radiotherapy head and neck cancer patients.