Incidence, clinicopathological features and outcome of primary central nervous system lymphomas. Population-based data from a Danish lymphoma registry. Danish Lymphoma Study Group, LYFO.

BACKGROUND

Primary Central Nervous System lymphomas (PCNSL), a rare neoplasm accounting for only a small fraction of malignant brain tumors and extranodal non-Hodgkin's lymphomas (NHL), seems to occur with increasing frequency in immunologically-normal as well as immunocompromised individuals. In an attempt to characterize the clinicopathological features, incidence rate and outcome of PCNSL, we here report our experience in a large unselected group of patients from a well-defined region.

PATIENTS AND

METHODS

In a Danish population-based NHL registry (LYFO) representing a population of 2.7 million, all new cases of NHL were registered during the 10-year period from 1st January 1983 to 31st December 1992. The number of malignant brain tumors reported to the Danish Cancer Registry from the region covered by LYFO, during the 7-year period from 1st January 1983 to 31st December 1989, is compared to the number of PCNSL.

RESULTS

During the 10-year period 2687 new cases of NHL were registered. Of these, 1004 (37%) were extranodal and 42 were non-AIDS-related PCNSL, accounting for 4.2% of extranodal NHL and 1.6% of all NHL, respectively. The incidence rate for PCNSL during the ten-year period (age range: 21-85 yrs, median: 62 yrs, M/F ratio: 0.9) was 15.6 cases per million population. Eighteen and 24 cases were diagnosed during the first and the second 5-year period, respectively (p > 0.05). During the 7-year period 1866 primary malignant brain tumors were registered in the region covered by the LYFO study group. In the same period 30 cases of PCNSL were detected. Thus, PCNSL accounted for 1.6% of all primary malignant brain tumors diagnosed in Western Denmark. Histologically, 83% were high-grade. Using the Kiel classification centroblastic diffuse (62%) and immunoblastic lymphoma (12%) were the most common subtypes. Thirty-seven patients had B-cell lymphoma; no T-cell lymphomas were detected. Forty-one cases were diagnosed pre mortem. Treatment included surgical resection (23 patients), whole brain irradiation (WBRT) (37 patients) and chemotherapy (22 patients). Median survival for those receiving either WBRT or WBRT and chemotherapy was 7.5 months and 12 months, respectively (p > 0.05). Survival was 43.9%, 31.7% and 7.3% at 1, 2 and 5 years.