Table 1. Characteristics of those with isolated (i-CNS) or combined (c-CNS) CNS relapses compared with those with an isolated bone marrow relapse (i-BM).
| c-CNS | i-CNS | i-BM | |
| N | 43 | 80 | 207 |
| Age at relapse in years | |||
| median (25th−75th) | 8·7 (6·8–13·7) | 8·4 (6·1–11·5) | 9·75 (7–13·4) |
| Range | 2·5–18·8 | 2·0–17·9 | 1·1–18·8 |
| Gender | |||
| Male:Female | 27∶16 | 61∶19 | 104∶103 |
| Ratio | 1·7∶1 | 3·2∶1 | 1∶1 |
| Time to Relapse in months | |||
| median (25th−75th) | 37 (23–47) | 27 (21–34·3) | 44 (33–61) |
| Range | 6–92 | 5–90 | 5–155 |
| Late | 20 (47%) | 12 (15%) | 142 (69%) |
| Early | 16 (37%) | 55 (69%) | 48 (23%) |
| Very Early | 7 (16%) | 13 (16%) | 17 (8%) |
| Risk category (%) | |||
| Standard | - | 12 (15%) | - |
| Intermediate | 20 (47%) | 68 (85%) | 135 (65%) |
| High | 23 (53%) | - | 72 (35%) |
| Immunophenotype | |||
| B:T | 36∶7 | 61∶19 | 189∶18 |
| Ratio | 5∶1 | 3∶1 | 11∶1 |
| CSF blast count | |||
| median (range) | 97 (14–188) | 97 (27–392) | NA |
| Bone Marrow Blast % | |||
| median (range) | 83·5 (48·5–95) | NA | 90 (78–95) |
| Cytogenetics (%) | |||
| progenitor B | |||
| Good | 15 (35) | 28 (35) | 77 (37) |
| Intermediate | 11 (25) | 18 (23) | 63 (30) |
| Poor | 5 (12) | 6 (8) | 34 (16) |
| Unknown | 5 (12) | 9 (11) | 15 (7) |
| T-cell | 7 (16) | 19 (24) | 18 (9) |
Relapses within 18 months of first diagnosis were termed as Very Early; after 18 months but within 6 months of stopping therapy as Early and after 6 months of stopping therapy as Late. B = progenitor B cell; T = T-cell; CSF = cerebrospinal fluid. CSF blast count is presented as cells/µl of CSF. Risk stratification and cytogenetic classification have previously been described.