Hypothyroidism in older patients with head and neck cancer after treatment with radiation: A population-based study

Background. In patients with head and neck cancer, radiation treatment (RT) is a risk factor for hypothyroidism. However, the specific magnitude of risk after RT in older patients is not known. Methods. We identified 5916 patients (age > 65 years) from SEER-Medicare diagnosed with head and neck cancer from 1992 to 2002. Proportional hazards models compared hypothyroidism risk after any RT versus surgery alone. Results. In patients treated with RT, 5-year incidence of hypothyroidism was 20% and 10-year incidence was 59%; in patients treated with surgery alone, incidence was 7% and 39% (p < .001). Patients treated with RT had increased adjusted risk (hazard ratio [HR] = 2.14; 95% confidence interval [CI] = 1.74-2.62), persisting for up to 10 years of follow-up (HR = 1.85, 95% CI = 1.39-2.44 from 5 to 10 years). Conclusion. In older patients with head and neck cancer, RT is associated with elevated hypothyroidism risk. As onset may be delayed for years, patients may require lifelong thyroid function screening after treatment.