Rising incidence of primary central nervous system lymphoma in Kumamoto, Japan

Background

Primary central nervous system lymphoma is an extranodal form of non-Hodgkin lymphoma arising in the craniospinal axis. The incidence of PCNSL is reportedly on the increase in some parts of the world in the last 2 decades.

Methods

We surveyed 4007 patients diagnosed with PIT between 1989 and 2004, with histologic diagnosis being obtained in 70% of the patients. Of these, the PCNSL cases were reviewed.

Results

Of 4007, 136 (3.4%) carried a diagnosis of PCNSL. At 0.41 per 100,000 per year, the age-adjusted incidence rate for that period was higher than that for the period from 1989 to 1998 (0.29 per 100,000 per year). Moreover, the number of patients with PCNSL doubled from 45 (1989-1996) to 91 (1997-2004).

Conclusions

Our findings point to an increase in the incidence of PCNSL among immunocompetent individuals in Kumamoto Prefecture.

Introduction

Primary central nervous system lymphomas are extranodal malignant lymphomas arising in the brain, spinal cord, leptomeninges, or eyes; at the time of diagnosis, patients are free of lymphoma outside the nervous system. Although PCNSL is invariably fatal without treatment, it is often highly responsive to therapy, and as many as 70% of patients reportedly achieve a complete response to initial treatments [4], [16]. Current treatments appear to improve the survival of PCNSL patients; however, disease recurrence and late neurologic toxicity are serious complications.

Primary central nervous system lymphomas account for less than 5% of all primary CNS tumors and for 1% to 2% of all lymphomas [14]. Over the last 2 decades, the incidence of PCNSL reportedly increased in some countries [2], [13], [17], [21], whereas in others, it remained stable [1], [7], [18], [21]. Although this suggests regional and/or ethnic differences, it is important to determine whether the increase in PCNSL is real or whether it represents an artifact because of the increasing population age, greater use of health resources, better diagnostic aids, and heightened awareness. We previously reported a population-based survey of intracranial brain tumors diagnosed between 1989 and 1998 in Kumamoto Prefecture, Japan [11]. In the present study, we evaluated current data to determine trends in the incidence of PCNSL in Kumamoto Prefecture.