Management of primary central nervous system lymphoma

Primary central nervous system lymphomas (PCNSLs) are predominantly high-grade diffuse large B-cell lymphomas. Incidence has been rising in immunocompetent as well as in immunocompromised patients, but main characteristics like age of onset, sex distribution, CT/MRI appearance and localization, molecular biology and morphology are different in both groups. These characteristics explain only in part the poor prognosis of the latter group. In today's neurosurgical practice PCNSL is regarded as a special entity among malignant brain tumors. This is due to the fact that surgical resection is no longer the treatment of choice ever since successful radio-/chemotherapy regimens have been introduced. Thus, in cerebral lesions suspicious of PCNSL, the histopathological diagnosis should be established by CT- or MRI-guided stereotactic biopsy or by CSF cytology. One should abstain from corticosteroid administration before stereotactic biopsy as this would mask the tumor's morphological appearance and possibly render an accurate histological diagnosis impossible. Postoperative tumor staging depends on the favored theory of histiogenesis. There is still a controversial discussion about the need to exclude systemic disease. Absolutely mandatory are a full clinical examination, enhanced CT or MRI images from the brain, CSF cytology, bone marrow biopsy, slit-lamp examination, and an HIV test. Today's therapy consists of corticosteroids and a methotrexate-based chemotherapy with adjuvant radiotherapy. As an exception, cyclophosphamide, methotrexate, procarbacine and dexamethasone (CMPD) administered after blood-brain barrier disruption with mannitol are at least as effective as multimodality treatment with methotrexate plus radiation therapy. More aggressive regimens did not prove superior regarding survival but result in a higher therapy-related complication rate.