Long-term survival in young women: hazards and competing risks after thyroid cancer

Background. Differentiated thyroid cancers (DTCs) are one of the most common and survivable cancers diagnosed in women. We examine factors associated with long-term survival and competing risks of death in women diagnosed with DTC under the age of 40 (<40) and aged 40 and older (40+). Methods. SEER data was used to identify DTCs diagnosed in women from 1975 to 2009. We examined overall (OS), disease-specific (DSS), other cancer (OCS), and non-cancer-related (NCS) survival using multivariate Cox proportional hazards modeling. Results. Observed survival was 97.2% for <40 (n = 14,540) and 82.5% for 40+ (n = 20,513). Distant stage (HR = 1.96, 95% CI 1.23-3.07), non-Hispanic Black (HR = 2.04, 95% CI 1.45-2.87), being unmarried (HR = 1.26, 95% 1.03-1.54), and subsequent primary cancers (HR = 4.63, 95% CI 3.76-5.71) were significant for OS in women <40. Age was an effect modifier for all survival outcomes. Racial disparities in NCS were most pronounced for young non-Hispanic black women (HR = 3.36, 95% CI 2.17-5.22). Women in both age groups were more likely to die from other causes. Conclusions. Age at diagnosis remains one of the strongest prognostic factors for thyroid cancer survival. More directed efforts to ensure effective care for comorbid conditions are needed to reduce mortality from other causes.