Conditioning regimens in autologous stem cell transplantation for multiplemyeloma: a comparative study of efficacy and toxicity from the Spanish Registry for Transplantation in Multiple Myeloma

High-dose chemoradiotherapy conditioning regimens for autologous stem cell transplantation (ASCT) are generally held to give similar results In multip le myeloma (MM), but no specific comparative study has been published. We a ddressed this issue by comparing the main high-dose chemoradiotherapy regim ens used in the Spanish Registry. Patient cohorts included 315 cases treate d with 200 mg/m(2) melphalan (MEL200), 127 patients with 140 mg/m(2) melpha lan plus total body irradiation (MEL140 + TBI) and 121 cases with 12 mg/kg busulphan plus 140 mg/m(2) melphalan (BUMEL). After ASCT, granulocyte and p latelet recovery time was similar in all conditioning groups. There were no differences in transplant-related mortality. All regimens yielded a simila r response in reference to pre-ASCT MM status, although BUMEL produced a sl ightly better overall response when compared with the other regimens (97% v s. 89% and 92%, P = 0.003). The 5-year overall survival (OS) with BUMEL was 47% [95% confidence interval (CI) 26-68] compared with 43% (CI 31-54) for MEL140 + TBI and 37% (CI: 18-56) for MEL200. The median survival for the BU MEL group was 64 months compared with 45 and 37 months for the MEL200 and M EL140 + TBI groups respectively. These differences were non-significant (P = 0.2). The median event-free survival (EFS) was better for BUMEL (32 month s) than for MEL200 (22 months) or for MEL140 + TBI (20 months), The differe nces in EFS between BUMEL and the other conditioning regimens reached stati stical significance (P = 0.01). Nevertheless, the adjusted multivariate ana lysis for OS and EFS revealed that the conditioning regimens had no indepen dent prognostic value. We concluded that three different conditioning regim ens, commonly used for ASCT in MRI, have a similar antimyeloma effect. Howe ver the trend for better results observed in our series with BUMEL requires a prospective trial.