Peripheral T-cell lymphoma (PTCL) incidence, proportions of subtypes, and survival differed markedly among racial/ethnic subpopulations in the United States, according to analysis of SEER cancer registries.
Compared with non-Hispanic whites, blacks had higher incidence rates overall of PTCL, due to higher rates of PTCL not otherwise specified (PTCL-NOS) (incidence rate ratio [IRR], 1.67; 95% CI, 1.53-1.82) and adult T-cell leukemia/lymphoma (ATLL) (IRR, 4.37; 3.42-5.56). By contrast, blacks had lower incidence rates of angioimmunoblastic T-cell lymphoma (AITL) and extranodal NK/T-cell lymphoma and natural killer–cell leukemia (ENKCL) than non-Hispanic whites. Underlying causes for these differences are not understood.
“Our findings also highlight the need for stronger efforts to increase recruitment of blacks into clinical trials of PTCL therapies,” wrote Dr. Scott Adams of Fred Hutchinson Cancer Research Center, Seattle, and colleagues (J Clin Oncol. 2016 Jan 25. doi: 10.1200/JCO.2015.635540).
Asians/Pacific Islanders and Hispanic whites had higher rates of ENKCL (IRR, 3.61; 2.93-4.42), and ENKCL comprised a larger proportion of PTCL (14%) in these populations than for non-Hispanic whites (3%), findings which reflect global variations. High rates of ENKCL may be influenced by both genetic and environmental factors, as 35% of this subpopulation was born outside the U.S., compared with 16% of all patients with PTCL. Epstein-Barre virus infection is associated with ENKCL.
Similar to global incidence patterns, Asians/Pacific Islanders had lower rates of anaplastic large-cell lymphoma (ALCL).
Higher incidence of ATLL among blacks and Asians/Pacific Islanders corresponded to a higher prevalence of human T-lymphotropic virus type 1 in these populations. Substantial differences in survival were also observed. Compared with non-Hispanic whites, survival with PTCL-NOS was shorter for every minority group, and blacks had worse prognoses for almost every histology. For patients with any PTCL, median survival time varied by race: 49 months for non-Hispanic whites, 24 for blacks, 22 for Asians/Pacific Islanders, 28 for Hispanic whites, and 36 for American Indians/Alaskan natives.
Reasons for survival disparities are not known, but contributing factors may include racial variations in pharmacokinetics or pharmacodynamics of therapeutic agents and genomic variations of the tumors, as well as healthcare disparities and socioeconomic factors.
The analysis used data from SEER cancer registries of 13,107 patients 15 years and older who had PTCL diagnosed in the U.S. between 2000 and 2012.
For non-Hispanic whites, the annual incidence rate of all PTCLs was 1.56 (95% CI; 1.52-1.59) per 100,000. Compared with non-Hispanic whites, incidence rate ratios were 1.32 (1.25-1.39; P less than .001) for blacks, 0.89 (0.83-0.95; P less than .001) for Asians/Pacific Islanders, 0.63 (0.49-0.79; P less than .001) for American Indians/Alaskan natives, and 0.96 (0.90-1.01; P = .13) for Hispanic whites.