Bortezomib and High Dose Melphalan Followed by Autologous Stem Cell Transplantation (BortHDM/SCT) for the Treatment of AL Amyloidosis: Results of a Feasibility Study.

Abstract 4353

AL amyloidosis is caused by a clonal plasma cell dyscrasia and is characterized by widespread, progressive amyloid deposition leading to multisystem organ failure and death. In this disease, amyloid protein deposits are derived from monoclonal immunoglobulin light chains. Aggressive treatment of AL amyloidosis with high dose intravenous melphalan followed by autologous stem cell transplant (HDM/SCT) is effective in inducing hematologic remission and clinical improvement. Furthermore, we have observed in ∼ 500 patients treated with HDM/SCT that achievement of a hematologic complete response (CR), i.e. disappearance of monoclonal gammopathy, normalization of serum free light chain ratio and clonal plasma cell dyscrasia, is a critical determinant of clinical improvement and prolonged survival. Bortezomib (Bor) has been reported to have activity in patients with AL amyloidosis. Furthermore, a synergistic effect between bortezomib and melphalan has been demonstrated in vitro and in vivo. Thus, the combination of bortezomib and HDM is a logical approach to study. Because of the importance of hematologic CR in treatment outcome, we conducted a feasibility study to determine whether addition of bort to HDM/SCT would be tolerable and would increase hematologic CR rates. Additional objectives of the study were to determine overall survival. Eligibility for entry into the trial required diagnosis of AL amyloidosis, age > 18 years, and adequate performance status (SWOG ≤ 2) and cardiopulmonary function (LVEF > 45%, DLCO > 50%). Peripheral blood stem cells were collected by leukapheresis following G-CSF mobilization, with minimum yields of 2.5 × 10⁶ CD34+ cells/kg required for participation in the trial. Bortezomib was administered at 1 mg/m² on D -6, D -3, D +1, and D +4 and HDM at 140-200 mg/ m² in two divided doses on D -2 and D -1. From 10/2008 to 7/2009, 8 patients were enrolled (median age 57, range 46-68; median number of involved organs 2, range 1-4). Of the 8 patients enrolled, 1 patient was removed from the protocol because of cardiac arrhythmia during stem cell mobilization and collection phase that precluded treatment with HDM/SCT. Of the 7 patients who received BorHDM/SCT, there was no treatment-related mortality within 100 days of SCT and there were no unexpected hematologic or non-hematologic toxicities associated with addition of bortezomib to HDM/SCT. The median times to neutrophil and platelet engraftment was D +10 and D +14 after SCT, respectively. Of 6 patients evaluable for early responses, normalization of serum free light chain levels and ratio occurred in 5 of 6 (83%) by D +14 and one patient achieved a 45% reduction in serum free light chain concentration at D +14. Of the initial 2 patients with longer follow-up, both have achieved a hematologic CR at 6 months following BorHDM/SCT. Follow-up is ongoing and hematologic responses appear to be well-maintained. Thus, this pilot study demonstrates that bortHDM/SCT is tolerable for selected patients with AL amyloidosis and leads to a high rate of hematologic responses.