The continuing increase in the incidence of primary central nervous system non-Hodgkin lymphoma: a surveillance, epidemiology, and end results analysis

Background: Primary central nervous system lymphoma (PCNSL) is an extranodal form of non-Hodgkin lymphoma arising in the craniospinal axis. The incidence of PCNSL appears to be increasing.

Methods: PCNSL incidence data from 1973-1997 were obtained from the nine Surveillance, Epidemiology and End Results (SEER) registries. To limit the influence of the human immunodeficiency virus on incidence rates, data of never-married males and females and persons of unknown marital status were excluded. As a surrogate for new technology, SEER data were reviewed by dates of diagnosis (surrogate for imaging) and compared with glioma incidence (surrogate for stereotactic neurosurgery and improved diagnostic neuropathology). Age-adjusted incidence rates were estimated and compared for the period prior to computed tomography (CT) (1973-1984) and the magnetic resonance imaging (MRI) period (1985-1997). The estimated annual percent change was calculated based on linear regression analyses using SEER*STAT.

Results: The incidence of PCNSL appears to be increasing in all SEER registries examined. All age groups demonstrated an increase over time. This increase was observed both in the CT era as well as in the MRI era. PCNSL age-adjusted incidence (0.15 to 0.48, a 3-fold increase) outpaced that of systemic lymphoma (14.1 to 18.5, a 33% increase) for the same registries over the same time periods. The rate of increase has begun to slow since 1985; the estimated annual percent change for PCNSL was three-fold higher during the period 1973-1985 compared with 1986-1997.

Conclusion: The incidence rate of PCNSL continues to rise. The increase is evident in all age groups and in both genders. Data from the current study suggest that improved diagnostic tools, such as CT or MRI, cannot explain this increase.