Association between development of hypothyroidism and improved survival in patients with head and neck cancer

Objective: To determine if the development of hypothyroidism has an effect on the outcome of advanced-stage head and neck squamous cell carcinoma. Design: Retrospective database analysis. Setting: Tertiary care center. Patients: The study population comprised 155 patients with advanced- stage head and neck squamous cell carcinoma. Interventions: Patients underwent radiation therapy alone or in combination with chemotherapy and surgery when indicated. Main Outcome Measures: Kaplan- Meier analysis was used to assess survival, not adjusting for timing of the detection of hypothyroidism. The following 2 analyses were then performed to adjust for the timing of detection: ( 1) hypothyroidism was assessed as a time- varying covariate in a Cox proportional hazards model and ( 2) a landmark analysis was conducted at 9, 12, 15, 18, 21, and 24 months using the Kaplan- Meier method. Results: Of the 155 patients, 59 developed hypothyroidism, defined as a thyrotropin level greater than 5.5 mIU/ L ( institutional value). An unadjusted Kaplan-Meier analysis indicated that patients who develop hypothyroidism have significantly better survival than patients who do not ( P <. 001, log- rank test). After adjusting for the timing of hypothyroidism, a Cox proportional hazards analysis indicated that survival was better, but not statistically significant, for patients who developed hypothyroidism ( hazard ratio, 0.62; P=. 12); results from a landmark analysis supported this finding ( P values ranged from.11 to.19). Conclusions: Development of hypothyroidism may be associated with improved survival and increased recurrence-free survival. Larger, prospective studies appear warranted to test the beneficial effect of hypothyroidism.