Lenalidomide maintenance after salvage in recurrent PCNSL. (A) Retrospective analysis of cohort of 10 relapsed PCNSL patients (median age, 61 years), reveals that the median response duration in CR 2-5 (after 1-4 previous relapses) with lenalidomide maintenance (5-10 mg/d; days 1-21/cycle) is ≥6 times longer than response duration after CR 1 in these patients with disease relapsing after standard induction therapies (P < .008; 95% confidence interval of ratio, 2.2-19.4). For 8 of these 10 patients with relapsed PCNSL, the longest response duration achieved with any intervention has been with lenalidomide maintenance. Five patients received salvage treatment with focal irradiation only, before lenalidomide (supplemental Figure 3), and 5 were retreated at last salvage with high-dose methotrexate at the same doses used during induction, before lenalidomide (Table 3). (B) Median overall survival is 45 months. With a median follow-up of 12.5 months, thus far, only 1 patient has progressed on lenalidomide to receive whole brain irradiation and 4 have succumbed to DLBCL. Patients on maintenance lenalidomide were closely monitored and examined in the clinic on an at least monthly basis for the first year, with restaging studies performed as indicated and with similar frequency as after previous therapies. Restaging MRI scans of the brain were performed in all 10 patients with a mean frequency of every 3.65 months; ophthalmologic examinations were performed for 6 patients at highest risk for ocular relapse (patients 1, 3-5, and 9-10) with a mean frequency of every 4 months (supplemental Table 5).