Dexamethasone (dex) maintenance versus observation (obs) in patients with previously untreated multiple myeloma: A National Cancer Institute Of Canada Clinical Trials Group Study: MY.7

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Abstract
6510 Background: DEX is an active drug in patients with previously untreated or relapsed multiple myeloma (MM). We conducted a phase III trial comparing DEX vs. prednisone in combination with melphalan as induction therapy; and pulsed monthly DEX vs. OBS as maintenance in previously untreated patients (pts) with MM. No differences in outcomes were observed in induction (ASCO 2001); we now report the results of maintenance therapy. Methods: Patients with symptomatic Durie-Salmon stage I, or stage II/III previously untreated MM were randomized to one of 2 induction regimens given for 12 cycles: arms 1 and 2 -melphalan 9mg/m2 po and prednisone 100 mg po daily for 4 days q 4 weeks; arms 3 and 4 - melphalan as above and DEX 40 mg for 4 days q 4 weeks. At initial randomization, pts were also allocated to receive, if they did not progress, either maintenance with DEX 40mg daily for 4 days q 28 days (arms 2 and 4) or OBS (arms 1 and 3). The primary endpoint was overall survival (OS) with secondary endpoints of progression free survival (PFS), toxicity and quality of life. Results: 307 pts who reached the maintenance phase are included in this analysis; 158 allocated to DEX, 149 to OBS. Pts were balanced in baseline patient and disease-related characteristics, and response to induction therapy. With a median follow-up of 35.3 months, 177 patients have died: (90 DEX and 87 OBS). No benefit in OS was observed (p= 0.74; HR = 0.92, 95% C.I. 0.69–1.24) with median survivals of 3.86 yrs and 3.65 yrs for DEX and OBS respectively. No difference in the cause of death between the two groups was noted. 234 pts have progressed or died (114 DEX, 120 OBS). PFS is superior in patients randomized to receive DEX (p= 0.0001; HR = 0.60, 95% CI 0.47–0.78). Median PFS is 2.76 yrs with DEX and 1.97 yrs with OBS. Conclusion: DEX as monthly pulsed therapy following induction with a melphalan-based regimen improves PFS but not OS in previously untreated patients with MM. These results should be considered in the design of future trials assessing maintenance therapy. No significant financial relationships to disclose.

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