With modern risk-adapted multi-agent chemotherapy, complete remission (CR) is obtained in the majority of children with acute lymphoblastic leukemia (ALL) and long-term survival free from disease can be expected in more than 70% of them. However, the prognosis of the patients without CR (induction failure; IF) has been dismal. We conducted a prospective study of F-protocol followed by a hematopoietic stem cell transplantation (SCT) in patients with IF.

Purpose: To evaluate the efficacy and safety of the treatment strategy adopted in the JACLS ALL F-protocol.

Patients and methods: Between April 1997 and March 2005, 1,254 patients with newly diagnosed ALL (excluding mature B-cell ALL) were enrolled on two consecutive JACLS ALL protocols (ALL-97 and ALL-02). Excluding induction death, 19 (1.6%) out of 1,207 patients with non-Ph+ ALL and 9 (30%) out of 30 patients with Ph+ ALL could not achieve CR following four- or five-drug induction chemotherapy. Among them, 25 patients in total were entered the study with guardian’s written consent. F-protocol consisted of the AML oriented re-induction chemotherapy (3 days of 8 mg/m2 MIT, 500 mg/m2 CA, and 40 mg/m2 PSL, followed by 3 days of 200 mg/m2 VP16, CA, and PSL a week later), four block consolidation therapy consisting of two alternative regimens A and B (A: HD-DEX, VP16, CA, MIT, B: HD-MTX, ASP, PSL, CA, THP-ADR) and maintenance therapy. Patients with CR were scheduled to receive SCT after the second consolidation therapy before the maintenance therapy. Transplant procedures depended on the institute.

Results: Following the re-induction therapy, 15 of 16 patients with non-Ph+ ALL (93.8%) achieved CR and 13 (86.7%) of them had continued CR until 27th week of treatment (CCR), which was the expected limiting time of SCT. Eight of 11 patients receiving SCT at the first CCR are alive. Two of 13 patients with CCR did not receive SCT by a physician’s decision, and relapsed during maintenance therapy. However they are alive following SCT in second CR. Five-year overall survival rate (OS) and event free survival rate for all 16 cases was 53% and 32.8%, respectively. Estimated five-year OS for patients receiving SCT at the first CCR was 59.7%. On the other hand, only 3 of 9 patients with Ph+ ALL (33.3%) achieved CR. No patients without response to re-induction therapy could achieve CR by any subsequent chemotherapy, but one success with SCT. Among 3 patients attaining a CR with re-induction therapy, 2 could continue CR and underwent SCT. One is alive in CCR and the other deceased from TRM. The other patient, relapsed during consolidation therapy, underwent SCT with success. Five-year OS for all 9 patients with Ph+ ALL was 33.3%. Concerning about adverse events of F-protocol, there was only one non-hematological toxicity NCI-CTC grade 4, which was pancreatitis due to ASP.

Conclusions: F-protocol could produce a high remission induction rate in non-Ph+ ALL, but not in Ph+ ALL. Improved outcome of non-Ph+ ALL patients with IF seemed to be obtained with F-protocol timely followed by SCT.

Disclosure: No relevant conflicts of interest to declare.

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