January 2001, Volume 15, Issue 1, Pages 50 - 56

Original Manuscript

Purified autologous grafting in childhood acute lymphoblastic leukemia in second remission: evidence for long-term clinical and molecular remissions A Balduzzi1, G Gaipa1, S Bonanomi1, M Dassi2, P Perseghin2, F Buscemi2, E D’Aniello1, A Rovelli1, R Schirò1, D Longoni1, A Rambaldi3, C Uderzo1 & A Biondi1 1Clinica Pediatrica Università di Milano-Bicocca, Ospedale San Gerardo, Monza, Italy     2Centro Trasfusionale, Ospedale San Gerardo, Monza, Italy     3Ematologia, Ospedali Riuniti, Bergamo, Italy     Correspondence to: A Balduzzi, Clinica Pediatrica Università di Milano- Bicocca, Ospedale San Gerardo, Via Donizetti 106, 20052 Monza (Milano), Italia; Fax: 39 039 230 1646

Keywords

acute lymphoblastic leukemia (ALL);   relapse;   autologous transplantation;   purging;   CD34+ negative selection

Abstract

Autologous transplantation is a treatment option for relapsed childhood acute lymphoblastic leukemia (ALL) in second complete remission (CR2) when a suitable donor is not available. In an attempt to prevent relapses originating from graft leukemic contamination, the experimental protocol of in vitro purification of leukapheretic products with monoclonal antibodies (MoAbs), previously reported for adults, was adopted in 11 of 12 consecutive patients (median age, 9 years) with B cell precursor ALL in CR2 after late relapse (median, 37; range, 31-51 months after the onset) enrolled between July 1997 and July 1999 at a single pediatric center. At a median of 12 days after the mobilizing chemotherapy followed by G-CSF, a median of 13.9 (range, 5.9-18.7) × 106 CD34+ cells/kg were collected from each patient and a median of 7.5 (range, 4.1-12.6) × 106 CD34+ cells/kg underwent the purification procedure. The first step of immunorosetting allowed a one-log reduction of the total cell count, by eliminating more than 90% of the CD11b+ cells; the second step, performed after incubation with anti-CD19 MoAbs, allowed the depletion of 99% (range, 93-100) of the CD19+ cells, kept within the magnetic field of the immunodepletion column, with a median recovery of 73% (range, 55-87) of the collected CD34+ cells. Molecular analysis assessed the in vitro eradication of detectable leukemic cells. A median reinfusion of 5.2 (range, 3.2-9.1) × 106 CD34+ cells/kg for each patient (median viability, 90%), after conditioning with the ‘TBI-VP16-CY’ regimen, allowed prompt engraftment and immunological reconstitution; no patients experienced severe transplant-related toxicity or major infections. One patient relapsed 7 months after transplantation, while 10 patients are alive in clinical and molecular remission, at a median follow-up of 29 months (range, 15-40) (2-year EFS, 89%, s.e. 9). In conclusion, the procedure proved to be reproducible for pediatric purified autografting, highly efficient concerning stem cell recovery and depletion of leukemia-lineage specific cells, and promising in terms of final outcome. Leukemia (2001) 15, 50-56.

Received 19 April 2000; Accepted 26 September 2000

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