Optimal detection of hypothyroidism in early stage laryngeal cancer treated with radiotherapy

BACKGROUND Hypothyroidism following radiation therapy (RT) for treatment of Head and Neck Cancer (HNC) is a common occurrence. Rates of hypothyroidism following RT for Early Stage Laryngeal Squamous Cell Carcinoma (ES-LSCC) are among the highest. Although routine screening for hypothyroidism is recommended; its optimal schedule has not yet been established. We aim to determine the prevalence and optimal timing of testing for hypothyroidism in ES-LSCC treated with RT. METHOD We conducted a population-based cohort study. Data was extracted from a prospective provincial head and neck cancer database. Demographic, survival data, and pre- and post-treatment thyroid stimulating hormone (TSH) levels were obtained for patients diagnosed with ES-LSCC from 2008-2012. Inclusion criteria consisted of patients diagnosed clinically with ES-LSCC (T1 or 2, N0, M0) treated with curative intent. Patients were excluded if there was a history of hypothyroidism before the treatment or any previous history of head and neck cancers. RESULTS Ninety-five patients were included in this study. Mean age was 66.1 years (range: 44.0-88.0 years) and 82.3% of patients were male. Glottis was the most common subsite at 77.9% and the average follow-up was 40 months (Range: 12-56 months). Five-year overall survival generated using the Kaplan-Meier method was 79%. Incidence of hypothyroidism after RT was found to be 46.9%. The greatest frequency of developing hypothyroidism was at 12 months. CONCLUSIONS We found a high prevalence of hypothyroidism for ES-LSCC treated with RT, with the highest rate at 12 months. Consequently, we recommend possible routine screening for hypothyroidism using TSH level starting at 12 months. To our knowledge, this is the first study to suggest the optimal timing for the detection of hypothyroidism.