Safety and Efficacy of Bortezomib (VELCADE™) in 104 Patients with Relapsed and/or Refractory Multiple Myeloma Who Have Received at Least Two Previous Lines of Therapy: Impact of Cytogenetics on Response from a Canadian Cohort.
Authors: Mikhael Joseph R. , Reece Donna E. , Belch Andrew , Bahlis Nizar J. , Sharma Deepa 
Published: October 2019

Background: Bortezomib (VELCADE™) is a reversible proteasome inhibitor that has been shown to be safe and efficacious in patients (pts) with relapsed and/or refractory multiple myeloma (MM) using a dose of 1.3 mg/m2 on days 1, 4, 8 & 11 of a 21-day cycle. Certain cytogenetic abnormalities are associated with poor prognosis in MM, including deletion 13, t(4;14) and the p53 deletion.(Stewart et al, JCO2005; 23(26):6339–44). Bortezomib has demonstrated the ability to overcome the poor prognosis associated with deletion 13 (Jagannath, JCO2005; 23(16S) 6501). The impact of bortezomib on a broader range of cytogenetic abnormalities, such as t(4;14) has yet to be determined.

Methods: In this multicentre, open-label, non-randomized, phase 3b study, pts with MM across 13 centres in Canada, who had received at least 2 previous lines of therapy and who were refractory to or had relapsed after their last therapy were enrolled. Pts received up to eight 3-week cycles of bortezomib on days 1, 4, 8 & 11. Dexamethasone 20 mg PO was administered on each day of and day after bortezomib administration if the pts either experienced progressive disease after receiving at least 2 treatment cycles of bortezomib or had no change in disease status from baseline after receiving at least 4 treatment cycles of bortezomib.

Results: 104 pts were enrolled; the mean age in this cohort was 60.7 years, and 65 (62.5%) were male. Approximately 30% of pts had a Karnofsky performance status of 70 or less at baseline. 71 pts (68.3%) had received prior thalidomide therapy, 32 (30.8%) had received a prior autotransplant and 4 (3.8%) had received prior bortezomib treatment. 74 (71.2%) received 3 or more lines of prior MM therapy. During the study, mean number of bortezomib cycles completed was 4.6 (range, 0–11 cycles), and the number of pts that completed 8 cycles of therapy was 36 (34.6%). 15.2% of pts received dexamethasone at cycle 3 and 19.2% at cycle 5. Cytogenetic analysis was performed on approximately half of the pts. Response data for cycle 5 is currently available for 69/99 (69.7%) of evaluable pts (see Table 1). Overall, 76.9% of the pts experienced Grade 3 & 4 adverse events. Safety profile observed is similar to past trial results with bortezomib.

Conclusion: In this large Canadian cohort of extensively pre-treated patients with mulitple myeloma, bortezomib demonstrated good response, consistent with previous studies. Analysis correlating cytogenetic profile and response rate is ongoing and will be available at the time of conference. In addition, a detailed safety analysis and impact of prior treatment on response will be analyzed and made available at the time of conference.

Table 1. Response to Bortezomib Category of Response* No. of Patients (%) *Modified SWOG: CR 100% M-protein reduction; R 75–99%; PR 50–74%; MR 25–49%; SD<25%, PD increasing M-protein Any Response (CR + VGPR + PR + MR) 47 (68.1) ---Complete Response (CR) + Very Good Partial Response (VGPR) ---22 (31.9) ---Partial Response (PR) + Minimal Response (MR) ---25 (36.2) Stable Disease 10 (14.5) Progressive Disease 12 (17.4)