Bortezomib-based induction therapy followed by intravenous busulfan–melphalan as conditioning regimen for patients with newly diagnosed multiple myeloma

Autologous stem cell transplant for multiple myeloma: Impact of melphalan dose on the transplant outcome

We evaluated impact of melphalan dose on transplant outcomes for multiple myeloma. Between 1995 and 2019 459 consecutive patients received a transplant; 69(15%) received melphalan ≤150 mg/m2 (Mel 150 cohort) and 390 (85%) melphalan 200 mg/m2 (MEL 200 cohort). The primary outcome was overall survival (OS) from the date of transplant. Progression-free survival (PFS), engraftment, transplant response, and cumulative relapse at 2 years were secondary outcome measures. Patients in Mel 150 cohort had adverse clinical and laboratory parameters at base line. Transplant response was better for Mel 200 cohort (p < 0.024). Median OS at a median follow-up of 88 months was similar in the two cohorts; 100 Vs 102 months (Mel 200), p = 0.817. Median PFS (60.0 Vs 53 months, p = 0.746), relapse at two years (32.4% Vs 30.9%, p = 0.745) and grade 3-4 mucositis (p = 0.823) were similar. Initial treatment prepares patients better for subsequent similar transplant outcomes despite differences in baseline characteristics.

Exploratory analysis of intensified conditioning as first line treatment for patients with high risk multiple myeloma

Multiple myeloma has extremely heterogeneous outcomes. Among prognostic factors, t(4;14) and del(17p) are rare oncogenic events associated with very poor prognosis. In an exploratory case-control study, we compared the combination of Busulfan-Melphalan or TBI-Melphalan with high dose Melphalan as a conditioning regimen in a series of 48 patients with del(17p) or t(4;14). These regimens were preceded by a Bortezomib-containing induction. Progression-free survival (PFS) was the primary endpoint whereas overall survival (OS) and complete response (CR) rate were the secondary endpoints. Twenty consecutive cases of high-risk myeloma received a reinforced conditioning regimen of Busulfan 0.8 mg/kg x4/j IV from day-6 to day-3 pre- graft (BuMel) or total body irradiation (TBI) 12 Gy (TbiMel), having received Melphalan 140 mg/m² at day-2 pre-graft. These cases were matched to 28 controls treated with Melphalan 200 mg/m² at day-2 (Mel200). After intensification ± consolidation, with a median follow-up of 6.3 years, the CR rate was higher in the BuMel/TbiMel group (65% vs 50%, P = .006). No differences were observed between both groups in terms of PFS and OS (P = .96). PFS in patients with a del(17p) mutation tended to be superior in the BuMel/TbiMel group. Our exploratory study shows that reinforcing the intensification regimen with Busulfan or TBI does not seem to improve the prognosis associated to t(4;14) and del(17p) abnormalities.

Conditioning with busulfan plus melphalan versus melphalan alone before autologous haemopoietic cell transplantation for multiple myeloma: an open-label, randomised, phase 3 trial

BACKGROUND

Retrospective studies suggest that conditioning therapy with busulfan plus melphalan could result in longer progression-free survival compared with melphalan alone in patients with multiple myeloma undergoing autologous haemopoietic cell transplantation (auto-HCT). We aimed to test this hypothesis in a randomised trial.

METHODS

The primary objective of the study was to compare progression-free survival with conditioning of busulfan plus melphalan with melphalan alone in patients with multiple myeloma. Patients with newly diagnosed multiple myeloma who were eligible for cell transplantation, aged 70 years or younger, with at least stable disease, were randomly assigned (1:1) to treatment. Patients received either busulfan plus melphalan, with a test dose of busulfan 32 mg/m² followed by pharmacokinetically adjusted doses on days -7, -6, -5, and -4 to achieve a target daily area under the curve (AUC) of 5000 mmol-minute and melphalan 70 mg/m² per day on days -2 and -1 (total melphalan dose 140 mg/m²), or a melphalan dose of 200 mg/m² on day -2. Randomisation was performed via a Clinical Trial Conduct Website at the University of Texas MD Anderson Cancer Center. The accrual is complete and final results are presented here. The study is registered with ClinicalTrials.gov, number NCT01413178.

FINDINGS

Between Oct 12, 2011, and March 22, 2017, 205 patients were assessed for eligibility and randomly assigned to treatment. The primary analysis of progression-free survival was measured in 202 patients who received treatment: 104 patients in the busulfan plus melphalan group and 98 patients in the melphalan alone group. 90 days after auto-HCT, 102 (98%) of 104 patients given busulfan plus melphalan and 95 (97%) of 98 patients given melphalan alone achieved partial response or better. The median follow-up in the busulfan plus melphalan group was 22·6 months (IQR 15·2-47·1) and 20·2 months (IQR 8·8-46·6) in the melphalan alone group. Median progression-free survival was 64·7 months (32·9-64·7) with busulfan plus melphalan versus 43·5 months (19·9-not estimated) with melphalan alone (hazard ratio 0·53 [95% CI 0·30-0·91]; p=0·022). There were no treatment-related deaths by day 100 in either group. Grade 2-3 mucositis was observed in 77 (74%) of 104 patients in the busulfan plus melphalan group versus 14 (14%) of 98 patients in the melphalan alone group.

INTERPRETATION

These findings, if confirmed in other ongoing studies, suggest that busulfan plus melphalan could replace melphalan alone as the conditioning regimen for auto-HCT in patients with newly diagnosed myeloma.

FUNDING

This study was funded in part by the National Institutes of Health (NIH) through MD Anderson's Cancer Center Support Grant (CA016672).