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.