MECp, a Salvage Regimen with Drugs Not Employed as Frontline Therapy, Allowed to Obtain a High CR Rate and to Bring to Unrelated Allogeneic Transplantation a High Proportion of Adult Patients with Relapsed ALL.
Authors: Borlenghi Erika , Cerqui Elisa , Cattaneo Chiara , Zuccalà Francesco , Galbiati Piero , Baushi Liliana , D'Adda Mariella , Rossi Giuseppe 
Published: October 2019

Abstract
Abstract 4101

Background and aim
The only curative option for adult patients with refractory or relapsed ALL is allogeneic haematopoietic stem cell transplant (allo-HSCT), which can offer a 28-34% long term survival in transplanted patients. However the actual feasibility of allo-HSCT is only 20-30% in unselected patients because of the low rate (30-50%) of complete remission (CR) achieved with salvage regimens (Tavernier, 2007- Thomas, 1999), the high rate of early relapse (Martino, 1999) and the difficulties in finding a suitable donor before progression (Davies, 1996). Hence, relapsed ALL can be actually cured in less than 10% of unselected adult patients. Using a second line treatment capable of obtaining a higher proportion of CR of longer duration may improve the dismal overall prognosis of patients. We report on the efficacy and toxicity profile of the combination of 6-metilprednisolone, mitoxantrone, etoposide and high-dose cytarabine (MECp), a salvage regimen containing cytostatic drugs to which patients had not been exposed during first line therapy, except for cytarabine at lower doses.

Patients and Methods
Between October 2000 and May 2009, 18 refractory/relapsed ALL patients were treated at our Institution with MECp regimen, consisting of a single course of etoposide 80mg/mq/die iv, cytarabine 1000mg/mq/die iv for 6 hours and mitoxantrone 6mg/mq/die iv 9 hours after cytarabine infusion for 6 days associated to metilprednisolone 50 mg/mq/die for 21 days, subsequently tapered to zero over one week. Three patients received an experimental sequential pulsed chemotherapy program in a multiinstitutional setting. At diagnosis, all patients had been treated according to the NILG-ALL 00/09 program (Bassan, Blood 2009). Four had been refractory to induction therapy and 14 had relapsed after a median of 12 months (range 3-43), 11 while on consolidation/maintenance, one after allo-HSCT, two after 3 and 12 months from the end of maintenance. There were 10 males and 8 females with a median age of 28 (range 17-64). ALL lineage was B in 9 cases (4 pro-B, 4 common, 1 pre B), T in 8 (5 pro-T, 3 cortical-TIII) and biphenotypic in 1. Molecular studies showed MLL/AF4 rearrangement in 3 and bcr/abl rearrangement in 3 cases, all before tyrosine-kinase inhibitors were available. Karyotypic abnormalities were present in 10 of 16 evaluable cases. Patients were treated in single/double bed rooms with reverse isolation. In 3 cases treatment duration was reduced to 4 days.

Results
CR was obtained in 13 of 18 patient (72,2%), independently of immunophenotype and time to relapse. CR rate was 100% in all ten patients with karyotypic abnormalities. Three patients (16%) died in aplasia during treatment, 2 of septic shock and 1 of unexplained shock. Two patients (T-ALL) were resistant. Recovery of neutrophils (>0,5×109/L) and platelets (>20×109/L) required a median of 22 days (range 17-37) and 28 days (range 21-45) from the start of therapy, respectively. Infections were documented in 9 of 18 (50%), being fatal in 2 (11%). Non-haematologic toxicity, mainly mucositis, was negligible. The median duration of CR was 5 months (range 2-5) which allowed 9 of 13 CR patients (69%) to undergo allo-HSCT (7 MUD, 1 HLA-identical sibling and 1 cord blood) after a median of 4 months (range 2-7) from CR. Reason for not being transplanted was failure of donor search in 4 patients who relapsed a median of 4 months. Causes of death included progressive disease in 7 patients, in 3 cases after HSCT, and transplant-related toxicity in 3 patients. The median survival of patients achieving CR was 13 months (range 7-33) and overall survival of the entire cohort was 8 months (range 1-33m).

Conclusions
With MECp, a combination of drugs not used during previous first-line therapy, a higher CR rate (72%) than commonly reported could be obtained, with acceptable toxicity. CR duration was long enough to allow 44,4% of patients to receive a non-family donor allo-HSCT, which is presently the best, yet still unsatisfactory, treatment option for adult patients with refractory/relapsed ALL.

Disclosures:
No relevant conflicts of interest to declare.