CLINICOPATHOLOGICAL FEATURES, SURVIVAL AND PROGNOSTIC FACTORS OF PRIMARY CENTRAL-NERVOUS-SYSTEM LYMPHOMAS - TRENDS IN INCIDENCE OF PRIMARY CENTRAL-NERVOUS-SYSTEM LYMPHOMAS AND PRIMARY MALIGNANT BRAIN-TUMORS INA WELL-DEFINED GEOGRAPHICAL AREA - POPULATION-BASED DATA FROM THE DANISH LYMPHOMA REGISTRY, LYFO, AND THE DANISH CANCER REGISTRY

It has been claimed that Primary Central Nervous System Lymphomas (PCN SL), a rare neoplasm accounting for only a small fraction of malignant brain tumors and extranodal non-Hodgkin lymphomas (NHL), occur with i ncreasing frequency in immunologically normal as well as in immunocomp romised individuals. In an attempt to characterize the clinicopatholog ical features, outcome and prognostic factors of PCNSL we here report our experience in a large unselected series of patients from a well-de fined region. In addition, we present data on trends in incidence of P CNSL and primary malignant brain tumors in a well-defined geographical area. In a Danish population-based NHL registry (LYFO) representing a population of 2.7 million all new cases of NHL were registered during the approximate 11-year period from 1st January 1983 to 31st May 1994 . Incidence data of primary malignant tumors of the brain and central nervous system in western Denmark for the period 1971-1990 have been o btained from the Danish Cancer Registry. During the approximate 11-yea r period 3124 new cases of NHL were registered. Of these, 1152 (37%) w ere extranodal and 48 were non-AIDS related PCNSL accounting for 4.2% of extranodal NHL and 1.5% of all NHL, respectively. The average annua l incidence rate of non-AIDS related PCNSL during the period was 1.56 cases per million population (age range: 15-85 yrs, median: 62 yrs, M/ F ratio: 1). In a 23-year period there was no trend towards an increas ing incidence of non-AIDS related PCNSL in a well-defined population. PCNSL accounted for 1.7% of all primary malignant brain tumors. Incide nce of primary malignant brain tumors was stable, except for age range s over 70 years. However, diagnostic artifacts might be responsible fo r this apparent increase. Histologically, 85% were high grade. Using t he Kiel classification centroblastic diffuse (60%) and immunoblastic l ymphoma(13%) were the most common subtypes. Forty-three patients had B -cell lymphoma and no T-cell lymphoma was detected. Forty-seven cases were diagnosed pre mortem. Treatment included surgical resection (26 p atients), whole brain irradiation (WBRT) (43 patients) and chemotherap y (28 patients). Median survival for those receiving either WBRT or WB RT and chemotherapy was 8 months and 20 months, respectively (p = 0.78 ). Overall survival was 53%, 38% and 26% at 1, 2 and 5 years. Cox-regr ession analysis identified only one factor having independent impact o n survival in PCNSL: performance score 12 (p < 0.001, RR = 5.8).