Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Background: The incidence rates for thyroid cancer have increased substantially over recent decades. Thyroid cancer diagnoses started to increase in the 1990s and peaked in 2013, primarily due to new diagnoses of papillary thyroid cancer. From 1983 to 2017, the female-to-male ratio of all thyroid cancers was 2.75:1, while the female-to-male ratio of small (<2 cm), localized papillary thyroid cancer was 4.28:1. There is a paucity of studies specifically on thyroid cancer outcomes in males. The current study used a US-based large database analysis to compare thyroid cancer characteristics and outcomes among male and female patients.
Methods: The National Cancer Database (NCDB) was utilized to conduct a retrospective cohort study. Male patients diagnosed with thyroid cancer between 2004 and 2013 were included, with follow-up data collection through 2018. A comparative cohort of female patients with the same inclusion criteria was also gathered. Comparative statistics, including t-tests and chi-squared analyses, were utilized to examine cohort demographics and differences in disease characteristics. Kaplan-Meier estimates of overall and recurrence-free survival were calculated. Multivariable Cox proportional hazard ratio models were completed for demographic and disease characteristics. All tests are two-sided, and the statistical significance level used was 0.05. Statistical analyses were carried out using SAS statistical software v9.4.
Results: Between 2004 and 2013, 71,666 male patients were diagnosed with thyroid cancer in the United States. There was 3.11:1 incidence rate of female-to-male thyroid cancer (female n=222,910). The mean age of males with thyroid cancer was 53.8, with 87.9% and 88.0% of patients being white and not Hispanic, respectively. Histologic diagnoses included 85.8% papillary, 8.9% follicular, 3.0% medullary, and 1.6% anaplastic thyroid cancers. These differed significantly from the proportions present in the female cohort: 90.5% papillary, 6.2% follicular, 1.3% medullary, and 0.7% anaplastic (p<0.01 for all). In the 52.3% of males with thyroid cancer with lymph nodes examined, 56.2% had cancer-positive lymph node findings, compared to a 37.3% positivity rate among female patients (p<0.01). Males with thyroid cancer had a 3.4% incidence of distant metastasis compared to 1.4% among female patients (p<0.01). AJCC pathologic staging classified just 55.2% of males with thyroid cancer as stage I compared to 73.6% of females (p<0.01) and, notably, 14.9% of males as stage IV compared to 6.0% of females (p<0.01). Five-year overall survival for males was 80.7% compared to 90.7% for females (p<0.01).
Conclusions: We found that male patients with thyroid cancer were more likely to have histologic subtypes that are associated with a worse prognosis. We also noted significantly higher rates of malignant lymphadenopathy, distant metastasis, and advanced AJCC stage. To date, this is the largest study of outcomes in males with thyroid cancer.