Intermediate-dose cyclophosphamide and bortezomib for PBSC mobilization in multiple myeloma

Although the incorporation of bortezomib into induction regimens has improved response rates in patients with multiple myeloma (MM), the role of bortezomib in the peripheral blood stem cell (PBSC) mobilization remains unclear. We assessed the PBSC mobilization efficacy, safety, and disease response of intermediate-dose cyclophosphamide and bortezomib in the PBSC mobilization. Twenty-one patients with newly diagnosed MM were enrolled in a phase II, non-randomized study that used bortezomib (1.3 mg/m2/day on days 1, 4, 8, and 11) and intermediate-dose cyclophosphamide (2 g/m2/day on days 2, 3) (Bor-ID-CY). The data from 15 patients who received intermediate-dose cyclophosphamide (ID-CY) were used as a historical control group. The total CD34 + cell yield of Bor-ID-CY and ID-CY groups were not significantly different (median 6.3 ×106/kg vs. 6.5 ×106/kg, p = 0.26). All three patients with mobilization failure of two groups had t(11;14). Six patients in Bor-ID-CY group were upgraded from a status that was less than a very good partial response (VGPR) at the time of PBSC mobilization to a VGPR or better after PBSC mobilization (p = 0.014). Four patients in Bor-ID-CY group developed sepsis. The time to engraftment was similar in the two groups. The addition of bortezomib to ID-CY did not impact the stem cell yield or quality.