Salvage Autologous Peripheral Blood Stem Cell Transplantation after the Development of tMDS or AML in Multiple Myeloma Patients

Multiple Myeloma (MM) patients are often treated with high-dose chemotherapy and autologous stem cell transplantation (ASCT) for disease control. Lenalidomide is typically used as maintenance but results in an estimated 3.3% chance of developing a therapy-related myeloid neoplasm (TMN) typically myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML). This complication is often devastating with a median survival for those with a TMN of just 13 months.

Over the past 6 years, 4 patients with multiple myeloma who developed a TMN were treated with a salvage ASCT using banked stem cells collected prior to their initial ASCT and before lenalidomide maintenance. None of these patients qualified for an allogeneic transplant. Melphalan 140 - 200 mg/m2 was used as conditioning prior to infusion of the peripheral blood stem cells, resulting in successful MDS/AML disease control.

Case 1 = 61-year-old man with MM initially treated with CyBorD then transplanted in 2010. Post transplant treatment included lenalidomide maintenance, followed by a variety of salvage regimens over the next 7 years including thalidomide, carfilzomib, daratumumab and pomalidomide. He developed cytopenias evaluated by bone marrow biopsy in May 2017. This showed tMDS (Karyotype 47-48, XY, der (5)t(5:20)(q11.1;q11.1), +19, der(21:22)(q10:q10),+2~3mar[cp11]/46-48,idem,-der(5),+20[cp5]/46,XY[4]. FISH confirmed deletion 5q in 76% and loss of chromosome 5 in 6.5% of cells. NGS showed a frame shift mutation of TP53 at a variant allele frequency of 92.5%. He underwent a second ASCT in Aug 2017 and recovered normal hematopoiesis within three weeks. Unfortunately, he developed an aggressive relapse of his multiple myeloma 9 months later and succumbed from refractory multiple myeloma 14 months after the salvage transplant, without evidence of MDS.

Case 2 = 72-year-old man with MM initially treated with CyBorD then an ASCT in May 2015. Lenalidomide maintenance was continued until October 2017 when he developed severe thrombocytopenia and circulating blasts. A bone marrow biopsy showed tMDS EB-1. Cytogenetics 46, XY t(3:21) (q26.2,q22) [18]/46, XY[2]. He received a second ASCT after melphalan 140 mg/m2 in Oct 2017 followed by recovery of normal blood counts. Bone marrow biopsy showed complete remission. He remains in remission from both the multiple myeloma and MDS almost 6 years later without any further therapy.

Case 3 = 65-year-old man with MM treated with bortezomib + dexamethasone followed by ASCT in Aug 2012. He received maintenance lenalidomide for 4 years but then progressed. In Jan 2018 he developed pancytopenia and bone marrow biopsy demonstrated MDS with ringed sideroblasts. Cytogenetics were normal but NGS showed mutations of ASXL1, RUNX1, SF3B1, SETBP1 and DNMT3A. He underwent a second ASCT using his banked stem cells after melphalan 140 mg/m2 in Jan 2018 followed by full hematopoietic recovery. A repeat bone marrow biopsy in March 2022 showed persistent MDS harboring ASXL1, SF3B1, and DNMT3A mutations, but no detectable RUNX1 or SETBP1 abnormalities. His multiple myeloma remains in remission >5 years later. He receives only intermittent erythropoietin to maintain a Hgb of 11.

Case 4 = 58-year-old man with MM initially treated with CyBorD followed by an ASCT in May 2014. He received lenalidomide maintenance but relapsed multiple times after 4 years ultimately complicated by renal failure requiring permanent dialysis. In March 2022 he developed pancytopenia. Bone marrow biopsy showed 15% blasts harboring del(5q), del(17p) and trisomy 8 by FISH. NGS demonstrated a mutation of ASXL1, and a copy number loss of TP53. Six months of decitabine did not improve his blood counts. In Dec 2022 he underwent a second ASCT after melphalan 140 mg/m2. A repeat bone marrow biopsy in Feb 2023 showed a complete morphological remission with a normal NGS. He is off all treatment 8 months post-transplant other than erythropoeitic support due to ongoing dialysis-dependent renal failure.

The development of TMN is an uncommon but devastating event in patients with multiple myeloma after ASCT and lenalidomide maintenance. These patients responded well to a salvage ASCT using banked stem cells. This approach was well tolerated and provided durable hematopoietic recovery. Second ASCT using banked autologous stem cells should be considered in such patients who are not otherwise candidates for allogeneic transplantation.