Natural Killer/T-cell Neoplasms: Analysis of Incidence, Patient Characteristics, and Survival Outcomes in the United States

Limited data are available regarding the incidence, survival patterns, and long-term outcomes of natural killer (NK)/T-cell neoplasms in the United States.We performed a retrospective study of patients with NK/T-cell neoplasms diagnosed from 2001 to 2014 using the Surveillance, Epidemiology, and End Results program database. The Kaplan-Meier method was used to estimate the overall survival difference among the subgroups. Multivariate analyses were used to determine the factors affecting survival.For the 797 patients with NK/T-cell lymphoma, nasal type, the median age at diagnosis was 53 years, and males tended to be younger at diagnosis (P .0001). The incidence of the disease increased from 0.4 in 2001 to 0.8 in 2014 per 1,000,000 individuals. The incidence was significantly greater in Hispanic patients compared with that in non-Hispanic patients (rate ratio, 3.03; P = .0001). The median overall survival was 20 months (range, 2-73 months) and varied significantly according to the primary site (P .0001) and the disease stage at diagnosis (P .0001). NK/T-cell lymphoma patients had an increased risk of acute myeloid leukemia (standardized incidence ratio, 18.77; 95% confidence interval, 2.27-67.81). For the 105 NK/T-cell leukemia patients, the median age at diagnosis was 58 years (range, 4-95 years). The overall incidence of the disease was 0.09 per 1,000,000 individuals and was significantly greater in males (rate ratio, 0.41; P .0001). Unlike NK/T-cell lymphoma, no racial disparities were found in the incidence. The median overall survival was 17 months (range, 0-36 months).The incidence of NK/T-cell lymphoma, nasal type, in the United States has at least doubled in the past decade, with the greatest predilection among Hispanics. Patients with NK/T-cell lymphoma might have an increased risk of the subsequent development of acute myeloid leukemia.