Bortezomib before and after high-dose therapy in myeloma: long-term results from the phase III HOVON-65/GMMG-HD4 trial.

The Dutch-Belgian Cooperative Trial Group for Hematology Oncology Group-65/German-speaking Myeloma Multicenter Group-HD4 (HOVON-65/GMMG-HD4) phase III trial compared bortezomib (BTZ) before and after high-dose melphalan and autologous stem cell transplantation (HDM, PAD arm) compared with classical cytotoxic agents prior and thalidomide after HDM (VAD arm) in multiple myeloma (MM) patients aged 18-65 years. Here, the long-term follow-up and data on second primary malignancies (SPM) are presented. After a median follow-up of 96 months, progression-free survival (censored at allogeneic transplantation, PFS) remained significantly prolonged in the PAD versus VAD arm (hazard ratio (HR)=0.76, 95% confidence interval (95% CI) of 0.65-0.89, P=0.001). Overall survival (OS) was similar in the PAD versus VAD arm (HR=0.89, 95% CI: 0.74-1.08, P=0.24). The incidence of SPM were similar between the two arms (7% each, P=0.73). The negative prognostic effects of the cytogenetic aberration deletion 17p13 (clone size ⩾10%) and renal impairment at baseline (serum creatinine >2 mg dl-1) on PFS and OS remained abrogated in the PAD but not VAD arm. OS from first relapse/progression was similar between the study arms (HR=1.02, P=0.85). In conclusion, the survival benefit with BTZ induction/maintenance compared with classical cytotoxic agents and thalidomide maintenance is maintained without an increased risk of SPM.

Contamination of autologous peripheral blood progenitor cell grafts predicts overall survival after high-dose chemotherapy in multiple myeloma.

BACKGROUND: Despite of the introduction of novel treatment modalities for multiple myeloma, high-dose chemotherapy with hematopoietic stem-cell rescue is still considered the standard of care for eligible patients <65 years of age. As we have previously reported, stem-cell grafts regularly contain quantities of plasma cells measurable by flow cytometry. However, the pathogenetic significance of this finding remains unknown. METHODS: Multiple myeloma patients (n = 60) were mobilized with chemotherapy and filgrastim. Peripheral blood stem cell grafts were obtained by standard leukapheresis, and the number of CD38++/CD138+ cells/kg was determined by flow cytometry. Plasma cell contamination above a threshold of 4.5 x 10(5) plasma cells/kg was considered "high", whereas lower quantities of plasma cells or absent plasma cells in the graft were considered "low". RESULTS: Progression-free survival: the median statistical progression-free survival was 33.5 months (range 11-99 months) in the high-contamination group (n = 16) versus 47 months (range 8-148 months) in the low-contamination group (n = 44). This difference turned out not to be statistically significant (P = 0.15). However, the difference was highly significant regarding overall survival with 53 months (range 11-119 months) in the high-contamination group and with 114 months (range 8-158 months) in the low-contamination group (P = 0.012). CONCLUSIONS: Patients with >4.5 x 10(5) plasma cells/kg contaminating the peripheral blood stem cell graft received after high-dose chemotherapy have a significantly reduced overall survival. Whether high contamination of grafts with plasma cells might reflect residual in vivo tumor mass prior to stem cell transplantation and a generally more aggressive behavior of malignant myeloma cells in these patients, or whether reinfused plasma cells contribute to an unfavorable course of disease remains to be determined.