Chemotherapy is superior to sequential hemibody irradiation for remission consolidation in multiple myeloma: a Southwest Oncology Group study

Abstract

Six hundred fourteen previously untreated patients with multiple myeloma were evaluated on this phase III Southwest Oncology Group (SWOG) trial. For remission induction, two noncross-resistant drug combinations (vincristine, melphalan, cyclophosphamide, and prednisone [VMCP] and vincristine, carmustine [BCNU], Adriamycin [doxorubicin; Adria Laboratories, Columbus, OH], and prednisone [VBAP]) were administered with either a direct alternating or a syncopated schedule. Pretreatment serum beta-2 microglobulin (beta 2M) was the single most important prognostic factor for survival (P less than .0001). There was no difference in toxicity, response, or survival by induction chemotherapy schedule (P greater than .7). For consolidation, 180 eligible and responsive patients were randomized to receive either an additional year of VMCP or sequential hemibody radiation (HBI) with vincristine and prednisone (VP) administered between the two HBI courses. Relapse-free survival (26 months) and overall survival (median, 36 months) were better with VMCP than with HBI (median, 20 months and 28 months; P = .04 and .018, respectively). HBI was also evaluated on a nonrandomized basis in 66 patients who achieved either a partial response (PR) or who were nonresponders to induction therapy. While HBI converted 24% of the PR patients to remission status, this effect was only seen in 5% of nonresponding patients. The survival of responsive and nonresponding patients receiving HBI was similar. All HBI groups had an inferior outcome to those receiving VMCP consolidation. Myelosuppression was also significantly worse after HBI. Survival from the time of relapse did not differ between patients randomized to receive VMCP or HBI. Thus HBI induced less durable remissions, but did not render patients less amenable to postrelapse chemotherapy. Our findings do not support the use of HBI in either chemotherapy responsive or nonresponding patients with multiple myeloma.