The Administration of Bortezomib, Dexamethasone and Thalidomide (VTD) after ASCT in Myeloma Patients Who Do Not Receive Bisphosphonates Normalizes sRANKL, Dickkopf-1 and Improves Abnormal Osteoclast Function and Impaired Angiogenesis.

Bortezomib (V) monotherapy has been associated with increased osteoblastic activity, reduced osteoclast function and decreased angiogenesis in relapsed/refractory myeloma. The effects of V on bones may be direct or may reflect the reduction of myeloma burden. The co-administration of zoledronic acid, in all reported studies to-date, may also suggest a synergistic stimulation on osteoclast/osteoblast interactions by the two agents but has not allowed the independent evaluation of V on bone metabolism. Previous studies have shown that the combination of V with other agents, such as thalidomide (T) and melphalan, although reduced osteoclast activity, did not enhance osteoblast function. We evaluated the effect of VDT consolidation therapy on bone metabolism and angiogenesis in myeloma patients who underwent high dose melphalan (200 mg/m²) followed by autologous stem cell transplantation (ASCT). In this prospective study, only patients in first remission or with primary refractory disease to one frontline treatment were included. Patients did not receive any bisphosphonate during or post-ASCT as throughout the period of VDT consolidation. VDT was given on day 100 after ASCT: V was administered at a dose of 1.0 mg/m² on days 1,4,8,11, while T was given at a dose of 100 mg/day, po, on days 1–21 and D at a dose of 40mg/day on days 1–4 of a 21-day cycle. Patients received 4 VDT cycles (first course) and 4 more VDT cycles (second course) 100 days post-day 21 of the 4^th cycle. Bone remodeling was studied by the measurement of a series of serum indices on day 1 of cycles 1 & 5 and on day 21 of cycle 8: i) osteoclast regulators [soluble receptor activator of nuclear factor-κB ligand (sRANKL) and osteoprotegerin], ii) osteoblast inhibitor dickkopf-1 (Dkk-1), iii) bone resorption markers [C-telopeptide of collagen type-I (CTX) and tartrate resistant acid phosphatase isoform 5b (TRACP-5b)], and iv) bone formation markers [bone-specific alkaline phosphatase (bALP) and osteocalcin (OC)]. Effect of VDT on angiogenesis was evaluated by measuring the serum levels of angiogenic cytokines, such as vascular endothelial growth factor (VEGF), angiogenin, angiopoietin-1, angiopoietin-2, and basic fibroblast growth factor (bFGF) on the same dates. The above biochemical markers and cytokines were also measured in 18, gender and age-matched, controls. To-date, 18 patients (7M/11F, median age 60 years) have been entered into this study. On day 100 after ASCT, just before VDT, 5 patients were in CR (2 in sCR), 11 in vgPR and 2 in PR, according to IMWG response criteria. At baseline, although the vast majority of patients were in ≥vgPR, they had increased serum levels of sRANKL (p=0.015), Dkk-1 (p=0.025), CTX (p=0.001), TRACP-5b (p=0.032), VEGF (p<0.0001), bFGF (p<0.0001), angiogenin (p=0.01) and reduced levels of angiopoietin-1/angiopoietin-2 ratio (p<0.0001) compared to controls. Serum levels of sRANKL strongly correlated with CTX (r=0.701, p=0.002) and OPG (r=0.733, p=0.0001), while levels of CTX correlated with TRACP-5b (r=0.619, p=0.0008). The administration of 4 VDT cycles resulted in a significant reduction of sRANKL (p=0.02), TRACP-5b (p=0.016), angiogenin (p=0.03), Dkk-1 (p=0.047), but also of bALP (p=0.003) and OC (p=0.016). A borderline reduction of CTX (p=0.071), and VEGF (p=0.056) was also observed. The levels of sRANKL, Dkk-1, TRACP and angiogenin did not differ from control values, while the reduction of bALP and OC did not produce significant differences compared to controls, after 4 VDT cycles. However, levels of VEGF, angiopoietin-1/angiopoietin-2 ratio and bFGF values continued to be elevated compared to controls’ values, while CTX levels were slightly increased compared to controls (p=0.049). The results of this on going study suggests that VDT consolidation post-ASCT normalizes sRANKL and Dkk-1 serum levels and improves impaired angiogenesis. However, as in other combination regimens (i.e. VMDT in relapsed/refractory patients), bortezomib could not produce an anabolic effect on bones when combined with TD even in these patients with low myeloma burden.