Allogeneic Myelo-Ablative Stem Cell Transplant (SCT) as Salvage Therapy of Reduced-Intensity Conditioned (RIC) SCT: Toxicity and Outcome.

RIC regimens are mainly used for patients who cannot benefit from the myelo-ablative (MA) approach, due to age, previous SCT, or comorbidities, based on an expected early toxicity of MA regimen. Some centers may also choose the RIC strategy in young patients because they have no facilities for the management of prolonged neutropenia. The development of RIC has been so encouraging that programs now compare MA and RIC in patients who could tolerate both approaches. However, RIC may fail, and MA SCT be secondary considered.

Objective: The goal of this retrospective survey was to assess the toxicity and outcome of MA after RIC SCT.

Patients: 17 patients (14–63 y; 6 CML, 4 AML, 2 CLL, 2 myeloma, 1 NHL, 1 CMML, 1 myelodysplastic syndrome) received a MA SCT after RIC, for relapse (n=12), graft rejection (n=4), or in a planned program (n=1), from an HLA-id sibling (n=12), a familial mismatched donor (n=1), an unrelated donor (n=3) or a cord blood (n=1). The reason for initial RIC approach was age in 4, a research program in 6, comorbidities in 3, and previous autologous SCT in 4 patients. RIC included Fludarabin (Flu)-Busulfan (BU) in 8, Flu-2Gy irradiation in 4, Cyclophosphamide (CPM)-antithymocyte globulin (ATG) in 1, and various Flu- regimens in 4. One patient had 2 consecutive RIC SCTs before MA SCT. The median delay between RIC and MA SCT was 9 months (range: 2.5–36 months). The same donor was used for the 1^st and 2^nd SCT in 12/17 cases. The MA transplant was conditioned with BU-CY (±VP16) in 9, Cyclo-TBI in 4, and other regimens in 4 patients. The median follow-up after MA SCT was 9 months

Results: After the MA transplant, 1 patient developed veno-occlusive disease, 2 developed interstitial pneumonia. Five patients died from relapse between 8 and 21 mo after the MA SCT. Seven (41%) died from transplant-related causes at a median of 8 months (GVHD:3; infection:1; multi-organ failure:1; thrombotic microangiopathy:1; EBV proliferative disease:1). 5/17 (29.5%) patients are alive and well 4.5 to 26 months after MA transplant. Three of them have extensive chronic GVHD while they did not develop any GVHD after RIC. The delay between the 2 transplants did not influence the outcome.

Conclusion: This survey shows that MA after RIC SCT is feasible, and considering that most of these patients have been initially eligible for RIC because of their age or comorbidities, MA SCT had an acceptable toxicity. It may be considered for patients who relapsed or rejected after RIC transplant.