Intensive salvage chemotherapy for primary refractory or first relapsed adult acute lymphoblastic leukemia: results of a prospective trial.

Background and Objective: Adults with primary refractory or relapsed acute lymphoblastic leukemia (ALL) have a very poor prognosis with current salvage chemotherapies. Complete remissions (CR) can be obtained with intensive regimens in 40-60% of cases, but they are short-lived. In an effort to obtain high CR rates and prolong their duration and achieve long-term survival in a substantial number of patients, we designed an intensive combination salvage regimen (RELAL-88). In this protocol, chemotherapy was to be followed by an allogeneic or autologous stem cell transplant (SCT) within three months from CR.
Design and Methods: Forty-five patients with primary refractory (n=17) or first relapsed ALL (n=28) were treated with the RELAL-88 five-day induction regimen comprising vindesine, mitoxantrone, cyclophosphamide, intermediate-dose Ara-C, prednisolone and methotrexate. Twenty-eight patients received granulocyte colony-stimulating factor (G-CSF), 16 patients from day 6 (early G-CSF group) and 12 from day 14 of therapy (delayed G-CSF group).
Results: Thirty-four patients (74%) achieved CR (95% CI 60-87), two died in aplasia due to infection and nine were non-responders. No pretreatment variable analyzed was predictive of the chance of obtaining CR. Recovery of neutrophils occurred at a median of 29 days from the start of chemotherapy without G-CSF and 20 days with G-CSF (p = 0.005), without differences between the early and late G-CSF groups. Non-hematologic side effects were usually well tolerated and consisted mainly of infections and mucositis. Twenty-three of 34 patients (68%) who achieved CR reached the planned SCT (nine autologous and 14 allogeneic). The median overall survival was 5.7 months, and the median disease-free survival for those achieving CR was 4.6 months. Of the variables analyzed for their influence on overall survival among the 34 patients who achieved CR, only the availability of an HLA-compatible sibling was associated with a prolonged survival (p = 0.03).
Interpretation and Conclusions: The RELAL-88 intensive salvage regimen produces a very high rate of CR in poor-risk adult ALL. Non-hematologic toxicities were tolerable, and most eligible patients could undergo the planned SCT. G-CSF significantly shortened the period of neutropenia by about eight days, irrespective of whether it was started early or late after chemotherapy. However, as with other currently available salvage therapies, remissions were short-lived, and more effective post-remission treatment strategies are needed. In our experience, only allogeneic SCT offered the chance of long-term survival.