Racial disparities of differentiated thyroid carcinoma: clinical behavior, treatments, and long-term outcomes

BACKGROUND The incidence of thyroid cancer in black Americans is significantly lower than that in white Americans, and the impact of race on the prognosis of thyroid cancer remains controversial. The purpose of this study was to determine the risk factors for survival in black and white patients and to compare the survival of differentiated thyroid carcinoma subtypes between these two races. We further investigated the association of lymph node and distant metastases with races. METHODS This is a retrospective analysis using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. A total of 70,346 cases were included in our study. Patients' demographics and cancer- and treatment-related characteristics were compared between the black and white Americans using chi-square and Fisher's exact tests. For multivariate analysis, Cox proportional hazards regression were used to assess the association between potential risk factors and the survival in black and white patients. RESULT Black Americans had a worse overall survival than white Americans (HR = 1.127, P = 0.002). While disease-specific survival (DSS) was comparable, the risk factors for DSS were different between white and black Americans. Black Americans had less lymph node metastasis of classical variant papillary thyroid carcinoma (CPTC, OR = 0.476, P < 0.001) and follicular variant papillary thyroid carcinoma (FVPTC, OR = 0.522, P < 0.001), but not follicular thyroid carcinoma (FTC). However, black Americans with FVPTC, but not CPTC or FTC, had a higher potential of distant metastasis (OR = 1.715, P = 0.026). Furthermore, only white patients with tumor > 2 cm and lymph node metastasis benefited from radioactive iodine. CONCLUSIONS The risk factors for DSS were significantly different in white and black patients. The impact of race should be considered in treatment strategy for thyroid cancer.