Relationship between ambient ultraviolet radiation and non-Hodgkin lymphoma subtypes: A U.S. population-based study of racial and ethnic groups

Associations between ultraviolet radiation (UVR) exposure and non-Hodgkin lymphoma (NHL) have been inconsistent, but few studies have examined these associations for specific subtypes or across race/ethnicities. We evaluated the relationship between ambient UVR exposure and subtype-specific NHL incidence for whites, Hispanics and blacks in the United States for years 2001-2010 (n=187,778 cases). Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated for UVR quintiles using Poisson regression. Incidence was lower for the highest UVR quintile for chronic/small lymphocytic/leukemia (CLL/SLL) (IRR=0.87, 95% CI: 0.77-0.97), mantle cell (IRR=0.82, 95% CI: 0.69-0.97), lymphoplasmacytic (IRR=0.58, 95% CI: 0.42-0.80), mucosa-associated lymphoid tissue (MZLMALT) (IRR=0.74, 95% CI: 0.60-0.90), follicular (FL) (IRR=0.76, 95% CI: 0.68-0.86), diffuse large B-cell (IRR=0.84, 95% CI: 0.76-0.94;), peripheral T-cell other (PTCL) (IRR=0.76, 95% CI: 0.61-0.95) and PTCL not otherwise specified (PNOS) (IRR=0.77, 95% CI: 0.61-0.98). Trends were significant for MZLMALT, FL, DLBCL, BNOS and PTCL, with FL and DLBCL still significant after Bonferroni correction. We found interaction by race/ethnicity for CLL/SLL, FL, Burkitt, PNOS and MF/SS, with CLL/SLL and FL still significant after Bonferroni correction. Some B-cell lymphomas (CLL/SLL, FL and Burkitt) suggested significant inverse relationships in whites and Hispanics, but not in blacks. Some T-cell lymphomas suggested the most reduced risk for the highest quintile of UVR among blacks (PNOS and MF/SS), though trends were not significant. These findings strengthen the case for an inverse association of UVR exposure, support modest heterogeneity between NHL subtypes and suggest some differences by race/ethnicity.