Racial/Ethnic Disparities in NK/T-Cell Non-Hodgkin Lymphomas in the US: A SEER Analysis
Authors: Kang Irene , Yang Dongyun , Park Mi Hee , Mohrbacher Ann , Tulpule Anil , Siddiqi Imran N , Ailawadhi Sikander , Kelly Kevin R. 
Published: November 2019

Background: NK/T cell non-Hodgkin lymphomas (NK/T NHL) are rare high-grade lymphomas that are diagnostically challenging and carry a poor prognosis. Incidence is notably higher in Asian countries as compared to North America and Europe. South Americans have an incidence similar to Asian countries though less well described. In this study we reviewed the incidence and outcomes of NK/T NHL in the US with a specific focus on patient race/ethnicity.

Methods: Surveillance, Epidemiology and End Results (SEER) database was used to examine the standardized incidence rates (SIR) of NK/T cell NHL among adult (≥18 yrs) patients diagnosed between 1992-2013. Mutually exclusive race/ethnicity categories were: African-Americans (AA), Asians/Pacific Islanders (API), Hispanic whites (HW) and Non-Hispanic whites (NHW). Cases that received a diagnosis at death certificate/autopsy, no follow-up records, or lacking age at diagnosis, sex, or race/ethnicity documentation were excluded. Age adjusted incidence rates (AAIR) were calculated by race. Cox proportional hazards models, adjusted for confounding variables, were used to evaluate association between patient demographics and overall survival (OS).

Results: A total of 706 cases met inclusion criteria. Of these, 64% were males and 36% females. AAIR was higher in males irrespective of race/ethnicity. Among different race/ethnic subgroups, API and HW had a higher AAIR than NHW and AA (0.2, 0.18, 0.05 and 0.04, respectively) (Figure 1). Median OS for males and females was similar (1.8 yr and 2 yr, respectively; p=0.76) There was a statistically significant difference in median OS by age for all patients with 4.3 yr for age 18-44 as compared with 0.8 yr for age >75 yr (p<0.001). Median OS by was different for HW (1.3 yr), API (1.8 yr), AA (2.3 yr) and HW (2.5 yr) but did not reach statistical significance (p=0.45). Median OS by stage varied as 7.3 yr for stage IE to 0.9 yr for all other stages combined (p<0.001) Cases with disease location as nasal cavity or sinus had a median OS of 3.5 yr as against 1.1 yr for those with all other sites (p<0.001) (Table 1).

Conclusions: Significant disparities exist in the US for NK/T NHL incidence by race and gender, with highest AAIR among the racial minorities of API and HW, which are fastest and second fastest growing minority groups in the US respectively. Increasing age, advanced disease stage and site outside of the nasal cavity or sinus are independent predictors of poor prognosis. Some differences do exist in survival by race. These factors need to be considered for better resource allocation and utilization for this rare, often incurable and aggressive disease.

Figure 1 Figure 1.

Disclosures

Ailawadhi: Pharmacyclics: Consultancy; Novartis: Consultancy; Amgen Inc: Consultancy; Takeda Oncology: Consultancy. Kelly:Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau.