Patient Characteristics
One hundred and sixty-eight patients enrolled on AALL02P2; of these, 2 were ineligible, 42 had an isolated testicular relapse (ITR), 122 had isolated CNS-R, and 2 had concurrent CNS and testicular relapse (Figure 1 ). Of the 122 isolated CNS-R patients, 118 had B-ALL and 4 had T-ALL. Results for patients with ITR have been reported previously.36 This report is limited to the iCNS-R patients with B-ALL.
The mean age at initial ALL diagnosis was 5.6 years, and mean age at enrollment on AALL02P2 was 8.1 years. At initial diagnosis, 35% of patients were classified as high risk (HR ALL) and 65% as standard risk (SR ALL) based on NCI/Rome criteria (SR: age 1-9.9 years of age with leukocyte count <50 x 109/L; HR: age> 10 years and/or leukocyte count> 50 x 109/L).