Exposure to carcinogens has been implicated in the development of non-Hodgkin lymphoma (NHL), suggesting that an examination of the environment on a population-based level might provide some insights. On that basis, researchers performed a study that found that living in an urban vs. rural area was associated with an increased risk of developing non-Hodgkin lymphoma (NHL) among diverse, urban populations.

The study, published online in Clinical Lymphoma, Myeloma & Leukemia, found an increased incidence of diffuse large B-cell lymphoma (DLBCL) in urban vs. rural Hispanics, and a similar increased incidence of chronic lymphocytic leukemia (CLL) in non-metropolitan urban non-Hispanic blacks.

A total of 482,096 adults aged 20 years and older with incident NHL were reported to 21 Surveillance, Epidemiology,and End Results (SEER) population-based registries for the period 2000 to 2016. Deanna Blansky of the Albert Einstein College of Medicine, Bronx, N.Y., and her colleagues compared patients by NHL subtype and urban-rural status, using rural-urban continuum codes from the U.S. Department of Agriculture.

The researchers found 136,197 DLBCL, 70,882 follicular lymphoma (FL), and 120,319 CLL cases of patients aged ≥ 20 years. The DLBCL patients comprised 73.6% non-Hispanic white, 11.8% Hispanic, and 7.3% non-Hispanic black, with a similar distribution observed for FL and CLL. Patients were adjusted for age, sex, and family poverty.

The study showed that, overall, there was a higher DLBCL incidence rate in metropolitan urban areas, compared with rural areas overall (incidence rate ratio [IRR] = 1.20, 95% confidence interval [CI] 1.11-1.30). Most pronounced was an increased DLBCL incidence among Hispanics in urban areas, compared with rural areas (rural IRR = 1.00; non-metropolitan urban IRR = 1.32, 95% CI 1.16-1.51; metropolitan urban = 1.55, 95% CI 1.36-1.76).

In contrast, metropolitan urban areas had a lower overall incidence of CLL than rural areas (8.4 vs. 9.7 per 100,000; IRR = .87; 95% CI .86-.89).

However, increased CLL incidence rates were found to be associated with non-metropolitan urban areas, compared with rural areas (IRR = 1.19; 95% CI 1.10-1.28), particularly among non-Hispanic Blacks (IRR = 1.49, 95% CI 1.27-1.72).

Unlike DLBCL and CLL, there were no differences observed in FL incidence rates by urban-rural status after adjusting for age, sex, and family poverty rates, the researchers reported.

“Overall, our findings suggest that factors related to urban status may be associated with DLBCL and CLL pathogenesis. Our results may help provide epidemiological clues to understanding the racial disparities seen among hematological malignancies, particularly regarding the risk of DLBCL in Hispanics and CLL in non-Hispanic Blacks,” the researchers concluded.

The study was sponsored by the U.S. National Institutes of Health. The researchers did not report conflict information.

SOURCE: Blansky D et al. Clin Lymphoma Myeloma Leuk. 2020 May 15; doi.org/10.1016/j.clml.2020.05.010.