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

We performed a retrospective population-based study to determine the epidemiology of natural killer (NK)/T-cell neoplasms in the United States. We found that the incidence of NK/T-cell lymphoma doubled during the past decade and is more common in Hispanic population. Unlike NK/T-cell lymphoma, no significant racial disparities were found in NK/T-cell leukemia. The risk of second primary acute myeloid leukemia might be increased for patients with NK/T-cell lymphoma. Background: Limited data are available regarding the incidence, survival patterns, and long-term outcomes of natural killer (NK)/T-cell neoplasms in the United States. Patients and Methods: 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. Results: 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). Conclusion: 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.