Treatment of High-Risk (HR) Philadelphia Chromosome-Negative (Ph-) Adult Acute Lymphoblastic Leukemia (ALL) According to Baseline Risk Factors and Minimal Residual Disease (MRD). Results of the PETHEMA ALL-AR-03 Trial.

Background and aim: Current therapeutic protocols for adult ALL consider MRD together with the baseline risk factors (age, WBC count, immunophenotype, cytogenetics) and speed in response to therapy for treatment decisions. On the other hand, the systematic use of allogeneic SCT for all adult patients (pts) with Ph- HR-ALL is still a matter of debate. The aim of the prospective study ALL-AR-03 from the Spanish PETHEMA Group was to evaluate the response to a differentiated therapy (chemotherapy or allogeneic SCT) according to early bone marrow blast clearance and MRD levels (assessed by cytofluorometry at the end of induction and consolidation therapy) in HR Ph- adult ALL patients.

Patients and methods: HR ALL included one or more of the following baseline parameters: age 30–60 yr, WBC count >25x10⁹/L and 11q23 or MLL rearrangements. Induction therapy included vincristine, prednisone and daunorubicin for 4 weeks. In pts with slow cytologic response to therapy (≥10% blasts in bone marrow assessed on d14) intensified induction with high dose ARA-C and mitoxantrone was administered. Early consolidation therapy included 3 cycles with rotating cytotoxic drugs including high-dose methotrexate, high-dose ARA-C and high-dose asparaginase. Pts. with slow cytologic response on d14 or MRD level >0.05% after consolidation were assigned to allogeneic SCT (related or unrelated) and those with standard cytologic response on d14 and MRD level <0.05% after consolidation received 3 additional cycles of delayed consolidation (identical to those of early consolidation) followed by maintenance therapy up to 2yr in CR.

Results: On June 2008,192 patients were evaluable (mean (SD) age 37(10) yr, 105 males, 119 precursor B-ALL, 73 T-ALL, WBC count 65(99) x10⁹/L). Induction death: 17(9%), resistance: 12 (6%), CR: 163 (85%). MRD<0.1% was observed in 64% of CR patients. Early consolidation was completed in 126 patients. MRD<0.05% was observed in 65% at the end of consolidation. On June 2008, allogeneic SCT was performed to 30 pts (15 from HLA-identical siblings and 15 MUD), TRM 11 pts, relapse 4, CCR 15. Delayed consolidation and maintenance was administered to 79 pts (toxic death 4 pts, relapse 21, CCR 54). Four-yr DFS for the whole series was 36±7% (37±19% for pts assigned to SCT and 56±12% for those assigned to chemotherapy). Slow cytologic response was associated with a lower CR probability and higher induction death. No baseline variable was associated with a higher probability of MRD negativity after induction or consolidation.

Conclusions: These results suggest that in HR Ph- adult ALL pts with adequate response to induction and adequate clearance of MDR the results of therapy are not hampered by avoiding allogeneic SCT. Supported by grants P-EF/07 from FIJC and RD 06/0020/1014 from Instituto Carlos III