Bortezomib and Thalidomide Treatment of Newly Diagnosed Patients with Multiple Myeloma - Efficacy and Neurotoxicity.

Introduction: As single agents, Bortezomib (V) and thalidomide (T) have activity in less than 50% of newly diagnosed myeloma (MM) patients whereas combinations with dexamethasone (D) with T (TD) and V (VD) demonstrated response rates of 63% and 85%, respectively. We sought to examine the anti-myeloma activity of VT, a steroid-free regimen. Considering the neurotoxicity of both agents, we examined the baseline neuropathy and progression of neurotoxicity post-VT.

Methods: Eligible patients had untreated Salmon-Durie Stage II/III MM and an ECOG performance status ≤2. V was given 1.3mg/m² i.v. on days 1, 4, 8, 11 every 21 days. T was started at 50mg daily and increased weekly to 150mg. Patients were treated for a minimum of 4 (evaluable), but to a maximum of 8 cycles. The neurologic evaluation utilized the reduced Total Neuropathy Score (rTNS), a validated scoring system combining symptoms, signs and nerve conduction studies. The rTNS was measured at baseline and after every 2 cycles. rTNS scores range between 0 to 32.

Results: 30 patients have been enrolled and 27 are evaluable for response. Median age is 59 (37–83), b2-microglobulin 3.3 (1.2–36.9), and albumin 3.6 (2.3–5.2). The mean dose of V was 1.11mg/m² and of T 110 mg/d. A dose reduction for ≥1 agent was required in all patients. Treatment was discontinued in 5 patients due to neurotoxicity, and 1 due to disease progression. A ≥ 50% reduction in M-spikes was observed in 82% of patients with 31% achieving undetectable levels. Median time to best response was 5 cycles (range 2–8). Clinical evidence of baseline peripheral neuropathy (PN) was noted in 15%, whereas 67% had abnormal baseline skin biopsies. By cycle 5 all patients developed PN: rTNS 2–8, (grade 1) 50%; rTNS 9–16 (grade 2) 31%; rTNS 17–24 (grade 3) 15%; and rTNS 25–32 (grade 4) 4%. There was no correlation between severity of PN and the cumulative V/T doses. Neuropathic symptoms improved with T/V dose reductions. Additional common adverse events (≥ grade 2) included fatigue 57%, constipation 52%, generalized pain 44%, and leg cramps 23%. Although the incidence of thromboembolic events with steroid-containing regimens ranges between 15–20%, no deep vein thromboses occurred in this study.

Conclusions: The VT combination achieved an 82% response rate in previously untreated multiple myeloma patients. No DVTs occurred with this steroid-free combination. This study established the baseline PN in newly diagnosed, untreated myeloma patients and demonstrated progression of neuropathy post-VT therapy. Future studies utilizing neuropathic preventive agents, lower doses of VT, or V in combination with other agents may yield similar disease responses with reduced neuropathic toxicities.