Related Vs Unrelated Donors After Auto-Allo Tandem Stem Cell Transplantation for Newly Diagnosed Patients with Multiple Myeloma.

Autologous stem cell transplantation followed by a dose-reduced conditioning and allogeneic stem cell transplantation from HLA-identical siblings has become a treatment option for patients with multiple myeloma. However, only a minority of the patients with multiple myeloma has an HLA-identical sibling and the experience using unrelated donor in this setting is limited.

From 1997 to 2007, 73 patients (male:45; female:28) with multiple myeloma stage II/III and a median age of 49 years (r, 29-64) were included in a prospective trial to determine the efficacy of a tandem auto-allogeneic stem cell transplantation SCT) from HLA-identical sibling (n=24) or unrelated donors (n=45). Unrelated donor were either fully HLA matched (n=29) or had one mismatch (n=16).Deletion 13q14 could be analyses in 64 pts was found to be positive in 66% of the pts. Del13q14 was more present in patient with unrelated (n=42) than with related (n=22) donors. Stem cell source was PBSC (n=69) or bone marrow (n=4). Induction-chemotherapy consisted of a median of 4 cycles anthracycline-based therapy in 60 pts, or of thalidomide- (n=3) or bortezomib- (n=8) based regimen. 6 pts did not respond to induction therapy and received salvage chemotherapy before autologous SCT. Conditioning prior auto SCT consisted of melphalan 200mg/m². After a median of 110 days (range 39-228) patients received a reduced intensity regimen with melphalan (140 mg/m²)/fludarabine regimen followed by allogeneic SCT from related (n=24) or unrelated (n=45) donors. GvHD prophylaxis consisted of anti-lymphocyte globulin (ATG-Fresenius®), cyclopsorin A and short course of MTX.

No primary or secondary graft failure was observed and leukocyte engraftment was achieved after a median of 15 days (range, 9-27), respectively. Acute graft-versus-host disease (GvHD) grade II to IV occurred in 38% and chronic GvHD in 22% of the patients. Limited GvHD was seen in 16 % and extensive GvHD was seen in 6 % of the patients. There was no difference regarding incidence of GvHD between HLA-identical sibling and unrelated donors. Overall response rate at day 100 was 94% including 55% complete remission (CR) and did not differ between related and unrelated SCT. Cumulative incidence (CI) of non-relapse mortality at one year was 20% (95% CI:11-29%) and did not differ between MUD and MRD (21 vs 17%, p 0.35). The cumulative incidence of relapse at 3 and 5 years was 30% (95% CI:19-41%) and 42% (95% CI: 29-55%), respectively with no difference between related and unrelated SCT at 5 years: 36 vs 44%(p= 0.6). The only significant factor for higher relapse incidence at 5 years was the presence of del13q14 (60 vs 20%, p= 0.007). After a median follow up of 40 months (r., 26-100), the estimated 5-year progression-free (PFS) and overall survival (OS) rates were 31% (95%CI: 19-43%) and 54% (95% CI: 42-64%), respectively, with no difference between related and unrelated SCT. Due to the higher relapse incidence only presence of del13q resulted in a significant worse 5- year OS and DFS (45 vs 77%, p=0.02 and 18 vs 57%, p=0.04).

Unrelated donors as stem cell source for auto-allogeneic tandem stem cell transplantation for newly diagnosed myeloma patients resulted in similar NRM, relapse-incidence, DFS and OS than HLA-identical sibling transplantation and can therefore be used as alternative stem cell source. Outcome after transplantation is better for patients lacking del 13q14.

No relevant conflicts of interest to declare.