Autologous Bone Marrow Transplantation for Acute Promyelocytic Leukemia in Second Remission: Prognostic Relevance of Pretransplant Minimal Residual Disease Assessment by Reverse-Transcription Polymerase Chain Reaction of the PML/RARa Fusion Gene

Reverse-transcription polymerase chain reaction (RT-PCR) of the PML/RARa fusion gene may predict relapse in acute promyelocytic leukemia (APL) patients in hematologic complete remission (CR). We have prospectively studied by RT-PCR 15 PML/RARa+ APL patients undergoing autologous bone marrow transplantation (ABMT) in second CR. The median time of first CR duration was 12 months (range, 6 to 40). All patients were reinduced with all-trans retinoic acid (ATRA), followed in 12 of 15 cases by mitoxantrone and Ara-C as consolidation. Fourteen patients received the BAVC (BCNU, Ara-C, m-AMSA, and VP-16) schedule as conditioning regimen. Unpurged marrows were collected immediately before conditioning treatment, analyzed by RT-PCR, and reinfused at median of 2 months (range, 2 to 7) from the achievement of second CR. Seven patients were PCR+ and eight PCR- for PML/RARa in their pretransplant marrows. All seven patients of the former group remained PCR+ during the follow-up and relapsed at a median time of 5 months (range, 2 to 9) from ABMT and 9 months (range, 4 to 14) from second CR. Of the eight PCR- patients, all remained PCR- during the follow-up controls. One patient relapsed at 10 months from ABMT, one died of a secondary (PML/RARa-) leukemia, and six are in hematologic and molecular remission at a median time of 28 months (range, 15 to 60) after ABMT and 32 months (range, 17 to 62) from second CR. Our results indicate that, in APL patients in second CR, ABMT with PML/RARa- marrow cells is likely to result in prolonged clinical and molecular remissions. Conversely, patients who test PCR+ after reinduction necessitate the use of alternative aggressive approaches, including unrelated allogeneic transplant.