Bone progression in multiple myeloma: Benefit of zoledronic acid for patients achieving at least Very Good Partial Response and prognostic value of bone turnover markers.

The Magnolia study demonstrated that continuation of zoledronic acid (ZOL) beyond 2 years reduces the risk of progressive bone disease (PBD) in patients with multiple myeloma (MM). This follow-up study investigated the effects of ZOL in patients achieving very good partial response (VGPR) compared to patients who did not and whether bone turnover markers could identify patients at an increased risk of PBD following treatment cessation. Two Magnolia trial subgroups were analysed: patients with VGPR or better after 2 years of ZOL, randomized to either continued treatment or observation, and patients randomized to observation in whom serial bone markers (C-terminal cross-linked telopeptide of type I collagen [CTX], procollagen type I N-terminal propeptide [P1NP], bone-specific alkaline phosphatase [BAP], tartrate-resistant acid phosphatase isoform 5b [TRAcP]) were measured for up to 4 years. Continued monthly ZOL beyond 2 years significantly reduced the risk of PBD (hazard ratio 0.40; 95% confidence interval [CI] 0.16-0.92) in patients with VGPR or better (subgroup 1). After ZOL discontinuation, bone markers increased gradually. Elevated CTX (≥0.30 μg/L) and TRAcP (≥4 U/L) levels were associated with increased 6-month PBD risk (29% and 15% respectively) (subgroup 2). Continuation of ZOL beyond 2 years seems to reduce skeletal progression risk in patients achieving VGPR or better. Elevated CTX or TRAcP levels may help identify patients who could benefit from re-initiating ZOL.