Increasing incidence of primary brain lymphoma in the US

There have been a number of clinical reports suggesting an increasing incidence of primary brain lymphoma unrelated to acquired immune deficiency syndrome (AIDS) and organ transplantation. To investigate this issue, the US incidence of this rare lymphoma was assessed using data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program (1973 through 1984). Never-married men, a relatively high risk group for AIDS, were excluded from the analyses. Brain lymphoma incidence increased from 2.7 in 1973 through 1975 to 7.5 cases per ten million population in 1982 through 1984 (chi-square trend, 15.25; P less than 0.001), and it increased among both men (chi-square trend, 6.74; P = 0.009) and women (chi-square trend, 10.48; P = 0.001). Increases in incidence also were observed among persons younger than 60 years of age (chi-square trend, 4.10; P = 0.04) and persons 60 years of age and older (chi-square trend, 9.16; P = 0.002). This increased incidence of brain lymphoma appears to be real: It antedates the AIDS epidemic and does not appear to be related to organ transplantation, another cause of increased risk of brain lymphoma. Although part of the increase may be an artifact of improvements in diagnostic technology and practice, most of the observed increase antedates the widespread use of such technologies. Finally, the increase in incidence of brain lymphoma does not appear to be related to overall trends in the incidence of brain tumors and non-Hodgkin's lymphoma, and it is not related to time trends in nosology.