An analysis of which subgroups of multiple myeloma patients, divided according to b(2)-microglobulin and plasma cell labeling index, benefit from high dose vs conventional chemotherapy.

Background and Objective: The clinical advantage of high-dose therapy (HDT) over standard treatment for multiple myeloma (MM) patients has been recently assessed. Which patient subgroups benefit most from this approach is unclear.
Design and Methods: To address this issue, the outcome of 54 patients under 55 years old treated with HDT was compared with that of 101 age-matched controls selected from 390 patients who received standard melphalan and prednisone (MP) chemotherapy in a national multi-center trial (M90 protocol).
Results: The complete response (CR) rate was 50% in the HDT group compared to 5% in the MP group. Event-free survival (EFS) was three times longer for the HDT patients (median 34.5 vs 12.2 months, p<0. 0001), though the controls enjoyed a prolonged survival after relapse, and hence there was no statistically significant difference in OS. Overall survival (OS) was analyzed in relation to to two major prognostic factors: b(2)-microglobulin (b(2)-M) and bone marrow plasma cell labeling index (LI). HDT significantly improved OS in poor prognosis patients with a high LI (>1.2%), (median 49.5 vs 32.5 months, p<0.03), whereas it did not prolong OS in poor prognosis patients with high b(2 )-M (> 3 mg/L).
Interpretation and Conclusions: In conclusion, HDT has a major impact on CR and EFS, and is the treatment of choice for patients with a high LI. Alternative strategies should be adopted in poor prognosis patients with high b(2 )-M.