Long-Term Follow-Up of a Randomized Phase III Multicenter Study Comparing a Standard Versus an Intensified Conditioning Regimen for High-Dose Chemotherapy in Patients with Multiple Myeloma.

High-dose chemotherapy (HDT) improves the outcome of patients with multiple myeloma (MM) in comparison to conventional chemotherapy. Dose-escalating strategies including tandem HDT are currently evaluated to further improve remission rates and survival of patients. Therefore we conducted a randomized multicenter trial to compare an intensified conditioning regimen with the current standard high-dose melphalan. The primary study endpoint was response rate, with overall survival (OS), event-free survival (EFS) and toxicity analysed as secondary endpoints. Between 1997 and 1999 a total of 56 patients with stage II and III disease, who were matched for age (median 56 years), number of previous therapies (median time from diagnosis to transplant 7 months) and different risk factors (beta2-microglobulin, LDH, CRP, cytogentic abnormalities, chemoresistant disease, IgA-subtype, renal impairment), were randomized. All patients received 2 courses of oral idarubicine/dexamethasone and 2 courses of intravenous cyclophosphamide/adriamycine in combination with G-CSF followed by peripheral stem cell collection. Thirty patients were treated with melphalan 200mg/m2 (HD-M) whereas 26 patients received idarubicine 42mg/m2, melphalan 200mg/m2 and cyclophosphamide 120mg/kg (HD-IMC) followed by autologous blood stem cell transplantation. Acute toxicity was higher with HD-IMC, including 5 (20%) treatment-related deaths due to infections versus none (0%) in the HD-M group. This lead to early termination of the study. Severity of mucositis (grade III-IV 19 vs. 8 pts., p=0.001), CRP (20 vs. 7 mg/dl, p<0.001), days of fever (11 vs. 3, p<0.001), days with iv-antibiotics (13 vs. 4, p<0.001), number of erythrocyte-transfusions (6 vs. 2, p<0.001), number of platelet-transfusions (16 vs. 4, p<0.001) and days to granulocyte engraftment (18 vs. 11, p=0.007) were significantly higher after HD-IMC. After a follow-up of 5 years analysis restricted to patients surviving the first 30 days after HDT showed a trend to higher response rates (CR+vgPR: 47% (95%CI 24–72%) vs. 35% (95%CI 18–56%), PR 37% (95%CI 17–63%) vs. 48% (95%CI 29–68%) and time-to-progression (median 31 vs. 15 months, p=0.1) in the HD-IMC treatment arm in comparison to HD-M, but there was no significant difference in EFS and OS (median 22 vs. 30, p= 0.31 and 66 vs. 66 months, p=0.8, respectively). Univariate analysis demonstrated that LDH levels > 200 U/L (p=0.04) and chemoresistant disease (p=0.05) were a bad prognostic factor for EFS. Beta2-Microglobulin levels > 5mg/dl (p=0.01), abnormal conventional cytogenetics (p=0.02) and LDH levels > 200 U/L (p=0.03) were predictive for an inferior OS. In conclusion intensified conditioning for HDT had an intolerable high treatment-related mortality and did not improve EFS and OS in patients with multiple myeloma.