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.