Primary central nervous system lymphoma in patients with AIDS

With the current imaging modalities available (CT, MR, proton MR spectroscopy, PET, Tl-201 brain SPECT), an accurate diagnosis and differentiation between PCNSL and infectious brain lesions in AIDS patients can be accomplished in the majority of the cases without having to wait for clinical response to medical therapy in cases of toxoplasmic encephalitis or without having to perform brain biopsy to reach a diagnosis. Exceptions to this statement are cases in which the patients do not respond to any medical treatment and the Tl-201 brain SPECT results are negative or conflicting. This early distinction, which is made possible by Tl-201 scan, is important because of the rapidity with which lymphoma spreads. Early detection can lead to earlier treatment. In AIDS patients with PCNSL, early radiation therapy has been reported to improve the survival from 3 to 10 months in up to 10% of the patients that complete a planned radiation treatment. Death in these patients usually is the result of opportunistic infection rather than PCNSL. Overall, in the experience of the authors' institution, Tl-201 brain SPECT has become the single most useful and cost-effective imaging study to differentiate PCNSL from infectious brain masses, particularly toxoplasmic encephalitis. The combination of CT, MR, and Tl-201 brain SPECT should establish noninvasively the most likely cause of a brain mass in an AIDS patient in greater than 95% of the cases.