Carfilzomib with dexamethasone (Kd) is a well-established regimen for the treatment of relapsed/refractory multiple myeloma (RRMM). There is limited information for the effects of Kd on myeloma-related bone disease. This non-interventional study aimed to assess skeletal-related events (SREs) and bone metabolism in patients with RRMM receiving Kd, in the absence of any bone-targeted agent. Twenty-five patients were enrolled with a median of three prior lines of therapy; 72% of them had evidence of osteolytic bone disease at study entry. During Kd treatment, the rate of new SREs was 28%. Kd produced a clinically relevant (≥30%) decrease in C-telopeptide of collagen type-1 (p = 0.048) and of tartrate-resistant acid phosphatase-5b (p = 0.002) at 2 months. This reduction was at least partially due to the reduction in the osteoclast regulator RANKL/osteoprotegerin ratio, at 2 months (p = 0.026). Regarding bone formation, there was a clinically relevant increase in osteocalcin at 6 months (p = 0.03) and in procollagen type I N-propeptide at 8 months post-Kd initiation. Importantly, these bone metabolism changes were independent of myeloma response to treatment. In conclusion, Kd resulted in a low rate of SREs among RRMM patients, along with an early, sustained and clinically relevant decrease in bone resorption, which was accompanied by an increase in bone formation, independently of myeloma response and in the absence of any bone-targeted agent use.
Keywords: C-telopeptide of collagen type 1 (CTX); bone disease; bone metabolism; carfilzomib; multiple myeloma; nuclear factor kappa-B ligand (RANKL); osteocalcin; procollagen type I N propeptide (PINP); skeletal-related events; tartrate-resistant acid phosphatase-5b (TRACP-5B).