Introduction: Bortezomib (Bz, VELCADE) is a proteasome inhibitor proven safe and effective for patients (pts) with relapsed and/or refractory multiple myeloma (MM). Pts in SUMMIT (NEJM2003;348:2609) and CREST (BJH2004;127:165) underwent rigorous testing (neurologic evaluations, FACT/GOG-Ntx questionnaires, nerve conduction studies) to determine the incidence, characteristics and reversibility of PN. In these phase 2 trials, the PN rate was 31–41% (grade [G] ≥ 3 in 11–12%). Specific dose modification (DM) guidelines for PN were not incorporated into the phase 2 trials but were developed for subsequent studies. The objective of this report was to evaluate the frequency, characteristics and reversibility of PN in an updated analysis of the randomized phase 3 APEX trial (NEJM2005;352:2487), in which specific DM guidelines for PN were implemented.
Methods: Pts with relapsed MM were randomized to Bz 1.3 mg/m2 IV on d 1, 4, 8, 11 q3wk for 8 cycles then 3 cycles on d 1, 8, 15, 22 q5wk, or dexamethasone (Dex) 40 mg PO on d 1–4, 9–12, 17–20 q5wk for 4 cycles, then 5 cycles on d 1–4 q4wk. Pts with G ≥ 2 PN were excluded. Data were collected on incidence, severity and reversibility of PN.
Results: Of 331 pts safety evaluable enrolled on Bz, 120 (36%) developed PN, including 30 (9%) with G ≥ 3. PN was classified as sensory or not specified in the vast majority of cases; motor neuropathies were rare. Of 91 pts with G ≥ 2 PN, 68 had DM, including 37 with doses reduced, held or schedule modification and 31 with Bz discontinuation (DC); 23 pts not following DM protocol. The majority (58 pts; 64%) of the 91 pts improved (9%) or had complete resolution (55%) of symptoms. Of 37 pts with DM without Bz DC, the majority (26 pts; 70%) had improvement, all with complete resolution of PN to baseline, with a median time to resolution of 78 d. Of 31 pts requiring Bz DC, 2 (6%) improved and 17 (55%) had complete resolution of PN with a median time to improvement/resolution of 121 d. Of 23 pts who did not follow the DM protocol, 12 (52%) had complete resolution with a median time to resolution of 106 d. The rates of PN (any G, G ≥ 3) were similar regardless of pt age or number/type of prior therapies (Table). The median TTP of 91 pts with G ≥ 2 PN, 68 pts with DM, and the Bz arm overall were 6.2, 6.9 and 6.2 months, respectively.
Conclusion: The overall rate of PN in APEX was similar to that of SUMMIT and CREST, but the rate of G ≥ 3 PN was lower, perhaps because of specific DM guidelines. PN was reversible in the majority of pts, and DM did not compromise efficacy. Pt age or number/type of prior therapies did not appear to affect the rate or severity of PN.
PN Bz Subgroup Any G*, % G ≥3, % *Bz related ge; 65 y 35 9 < 65 y 37 9 > 1 prior therapy 36 10 1 prior therapy 37 8 Steroids 38 7 Alkylating agent 35 7 Anthracycline 39 7 Vinca alkaloid 38 8 Thalidomide 44 8 Transplantation 37 7
