Treatment of primary CNS lymphoma

Primary central nervous system lymphoma is a particular challenge in clinical neuro-oncology. In contrast to most other malignant brain tumors, it may be considered a curable disease at least in younger patients who can tolerate intensive treatment regimens. Yet, therapeutic progress has been limited with little measurable improvement in outcome over the last two decades, mainly due to the low incidence of this tumor, which impedes the execution of large randomized clinical trials, and the failure of most large cooperative groups to conduct such trials. Whenever possible, high-dose methotrexate (HD-MTX) is the backbone of the therapeutic regimen. Response rates can be increased by the addition of second agents like ifosfamide or cytarabine, however, their impact on overall survival is less clear. Similarly, the use of the anti-CD20 antibody rituximab, commonly used in the treatment of B cell lymphomas outside the CNS, remains controversial and has not been examined in adequate clinical trials. The prognosis of patients, who do not qualify for HD-MTX-based chemotherapy, is considerably poorer. Radiation therapy is an active treatment with high response rates but does typically not result in long-lasting remissions. It remains an important therapeutic option as a salvage therapy in patients progressing on or no longer responding to HD-MTX-based treatment. The combination of HD-MTX and radiation therapy does not prolong overall survival. It is associated with significant neurotoxicity, and it should be avoided. Another matter of debate is whether consolidation therapy by other means, such as high-dose chemotherapy followed by stem cell support, is the most promising regimen. Given these numerous uncertainties, neuro-oncologists should strive for a treatment of PCNSL patients within clinical trials to allow for the development of improved therapeutic regimens.