Non-Hodgkin's Lymphoma Incidence: A Comparison of Demographic Patterns and Temporal Trends Between Pennsylvania and SEER Registries

Objective: Previous analyses of Surveillance Epidemiology and End Results (SEER) data have documented striking time-related increases in non-Hodgkin's lymphoma (NHL) incidence in the United States. Using data from the Pennsylvania Cancer Registry (PCR), which is not part of SEER, this study evaluated whether patterns of NHL differ in these two areas. Methods: Joinpoint and age-period-cohort (APC) regression models were applied to summarize gender- and race-specific NHL incidence time trends in Pennsylvania and the SEER registries between 1985 and 2004. Multiple regression analysis was used to identify demographic factors associated with age-adjusted county-specific NHL patterns in Pennsylvania. Results: According to APC analyses, Pennsylvania NHL incidence increased, on average, 1.5% and 2.5% annually in white and black men and 1.6% and 3.2% annually in white and black women. Average annual increase of gender- and race- specific NHL incidence in the SEER registries was similar to the PCR, except for white men (0.3% per year). Diffuse lymphoma appeared to be the most important contributor to the increase of NHL incidence in PCR and SEER registries. In Pennsylvania, NHL incidence was higher in counties with a greater percentage of urban residents (p=0.005). Conclusion: Though not identical, NHL incidence patterns in Pennsylvania and the SEER registries were generally parallel. The ecologic association observed in Pennsylvania NHL incidence and urban residence may be relevant to NHL patterns in the entire United States. Future work should explore what aspects of urbanization may account for the association with increased NHL risk.