Clinical Risk Factors for Peripheral Neuropathy in Patients Treated with Subcutaneous or Intravenous Bortezomib for Newly Diagnosed Multiple Myeloma

Background:

Peripheral neuropathy (PN) is an important, dose-limiting toxicity of bortezomib (BTZ). Subanalysis of the phase 3 VISTA trial of intravenous (IV) BTZ in newly diagnosed MM patients identified baseline neuropathy as only clinical risk factor for Bortezomib-induced peripheral neuropathy (BiPN). Since subcutaneous (SC) application reduces rates of BiPN, BTZ is mainly applied subcutaneously in current clinical trials and general practice. Data on clinical risk factors for BiPN in the era of SC BTZ are limited. We analyzed risk factors for PN in patients treated with SC or IV BTZ in the prospective randomized MM5 phase III trial of the German Myeloma Multicenter Group (GMMG).

Methods:

Primary end-points of the MM5 trial were response to VCD (BTZ 1.3 mg/m², days 1, 4, 8, 11; Cyclophosphamide 900 mg/m² IV; day 1, Dexamethasone 40 mg/d, orally, days 1-2, 4-5, 8-9, 11-12) compared to PAd (BTZ 1.3 mg/m², days 1, 4, 8, 11; Doxorubicin 9 mg/m² IV, days 1-4; Dexamethasone 20 mg/d, orally, days 1-4, 9-12, 17-20) induction therapy with respect to remission and progression-free survival (PFS). Induction therapy was followed by stem cell mobilization and harvest, high-dose therapy and Lenalidomide-based consolidation/maintenance therapy. From 07/2010 until 11/2013, 604 patients were randomly assigned to receive 3 cycles of PAd or VCD. Based on the results by Moreau et al, administration of BTZ was changed from IV to SC in 02/2012 after 314 patients were enrolled. We performed univariate and multivariate testing to analyze the association of different factors with the occurrence of PN ≥ grade 2 according to NCI CTCAE version 4.0 after completion of induction therapy. Factors included: Treatment arm (PAd vs. VCD), route of administration (IV vs. SC), existing baseline PN as well as baseline ISS, creatinine ≥2.0 mg/dl , body mass index (BMI), hemoglobin and calcium levels. Fisher's exact test was used for univariate analyses. A multivariate logistic regression model was adapted to analyze the influence of all factors on the occurrence of PN. In this model the impact of a single factor on PN is measured by an odds ratio (OR) based on a characteristic effect (change of one unit for categorical factors and change of interquartile range for continuous factors).

Results:

Of the analyzed patients, who received at least one dose of trial medication (PAd: n=150 IV/140 SC; VCD: n=154 IV/140 SC), 61 patients (10.2%) developed PN ≥ grade 2. Rates of PN were higher in patients treated with PAd (n=40; 13.5%) compared to VCD (n=21; 7.0%). Neither the presence of higher ISS stage at baseline, nor the route of administration had an impact on development of PN after 3 cycles of induction therapy in univariate analyses. However, PN was more frequent in IV-treated patients during the third cycle of induction therapy (IV: 7.6%; SC: 1.8%, p = 0.001). Median baseline BMI was significantly higher in patients who developed PN (26.9 kg/m²; 19.5-43.7 kg/m²) compared to patients without PN (25.7 kg/m²; 16.7-44-6 kg/m², p=0.04). Also baseline hemoglobin levels were higher in patients with PN (12.0 g/dl; 6.8-15.9 g/dl) compared to patients without PN (10.8 g/dl; 5.8-16.3 g/dl, p=0.004). While baseline calcium levels were significantly lower in patients with PN (2.3 mmol/l; 1.6-3.5 mmol/l) compared to patients without PN (2.4 mmol/l; 1.6-5.4 mmol/l, p=0.04), baseline creatinine were not different in both groups. Multivariate logistic regression adjusting for the above mentioned factors confirmed the effect of VCD treatment compared to PAd on the development of PN (OR 0.49, 95% confidence interval (CI) [0.28, 0.89], p=0.02) and the importance of pre-existing PN (OR 3.12, 95% CI [1.26, 7.76], p=0.01). Also baseline calcium (OR 0.71, 95% CI [0.51, 0.99], p=0.04) and hemoglobin levels (OR 1.53, 95% CI [1.01, 2.33], p=0.05) proved to have an impact on the development of PN in the multivariate model.

Conclusion:

We confirm the importance of pre-existing neuropathic symptoms and the combination partners for BTZ on the development of PN in patients with newly diagnosed MM. We provide first evidence that clinical baseline characteristics, like calcium and hemoglobin levels, might predict the development of PN. This is in line with preclinical studies showing that dysregulation of calcium homeostasis and oxidative stress in the dorsal root ganglion plays a role in the pathogenesis of BiPN.