Once considered to be a rare tumor, primary CNS lymphoma ( PCNSL )now ae且 icts approximately 300 people in Japan each year . PCNSLs completely regress With corticosteroid or irradiation , but soon recuL Median survival time of PCNSL patients has been reported to be 10 to 18 months by radiotherapy alone . The current treatment rec − ommendation is systemic high − dose methotrexate followed by whole cranial irradiation treatment . This strategy produces a response rate of 80 − 90 % and an MST of

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... ore than 30 months . However , improved survival overshad − ows treatment efficacy especially in the elderly patients over 60 years of age in whom delayed therapy − related neu − rotoxicity is observed frequently . Multi − institutional prospective trials will ensure the establishment of a consen − sus for therapy of this disease based on age and other prognostic factors . (