A Randomized Comparison of Total-Marrow Irradiation, Busulfan and Cyclophosphamide with Tandem High-Dose Melphalan in Patients with Multiple Myeloma.

Background Myeloablative chemotherapy with support of autologous peripheral blood stem cells (APBSC) has widely been accepted as a standard of care in patients (pts) with newly diagnosed multiple myeloma (MM). High-dose (HD) melphalan (Mel) 200 mg/m² was considered superior to total-body irradiaton (TBI) plus Mel 140 mg/m² for toxicity reasons. Since MM plasma cells are inherently responsive to irradiation, our group evaluated TBI aimed at reduced organ toxicity by shielding lungs and liver (total-marrow irradiation [TMI], 9 Gy) combined with busulfan (Bu, 12 mg/kg) and cyclophosphamide (Cy, 120 mg/kg) in a previous phase I/II trial (Einsele et al, Bone Marrow Transplant, 2003).

Patients and methods In the current study (DSMM I), subjects with previously untreated MM in Durie-Salmon stages II/III were randomly assigned to either receive one course of TMI/Bu/Cy versus two cycles of HD Mel 200 mg/m² each with APBSC transplantation if having had an adequate number of stem cells collected and at least stable disease. Primary end point was event-free survival (EFS), secondary end points overall (OS) and disease-free survival (DFS).

Results A total of 294 pts (median age, 54 years), 246 of whom completed stem cell harvest were enrolled between 8/1998 and 1/2002 by 46 centres. Eventually, 198 (n=100 TMI/Bu/Cy and n=98 HD Mel) pts were randomized and included into the ITT population. The safety population (n=80 TMI and n=118 HD Mel, due to 18 pts switching to Mel) was analyzed for toxicity and response. CR rate before HD therapy was 7.0% (7/100) in the TMI and 6.1% (6/98) in the Mel arm respectively. Significantly more pts receiving TMI/Bu/Cy experienced WHO grades 3 and 4 pulmonary and gastrointestinal toxicity and pain. Following HDT, CR rate increased to 17.5% (14/80, TMI) and 32.2% (38/118, HD Mel; p=.022) respectively. After a median follow-up of 1447 days, median EFS in the TMI group was 1161 days versus 1090 days for HD Mel (p=.812). Probability of 4-year OS was 72.7% (95%-CI: 62.1–80.7) with TMI and also 72.7% (95%-CI: 61.7–81.1) after HD Mel (p=.754). For pts in CR following HD therapy, probability of 4 year DFS was 62.4% (95%-CI: 33.6–81.6) for TMI vs. 50.4% (95%-CI: 30.6–67.3) for HD-Mel (p=.138).

Conclusion In this randomized trial on pts with newly diagnosed MM, the irradiation-based regimen was associated with more pulmonary and GI toxicity when compared to HD Mel. Incidences of other toxicities including hepatotoxicity, however, were not different between the two treatment arms. CR rate was superior for HD-Mel, while there was no difference in OS and EFS between the two treatment arms. Subjects achieving CR may be more likely to enjoy prolonged DFS after TMI/Bu/Cy.