Subcutaneous Versus Intravenous Bortezomib in Two Different Induction Therapies for Newly Diagnosed Multiple Myeloma – Subgroup Analysis from the GMMG-MM5 Trial

Background:

In patients with relapsed multiple myeloma (MM), Moreau and colleagues (Lancet Oncol, 2011) demonstrated that subcutaneous (SC) administration of bortezomib (BTZ) significantly reduced rates of adverse events (AE) compared to the intravenous (IV) formulation without loss of efficacy. Prospective data on SC BTZ in newly diagnosed MM are limited. We investigated the impact of SC versus IV BTZ in two different induction therapies for patients with newly diagnosed MM treated within the multicenter, prospective randomized MM5 trial of the German Myeloma Multicenter Group (GMMG).

Methods:

From 06/2010 until 11/2013, 604 patients were randomly assigned to receive 3 cycles of PAd (BTZ 1.3 mg/m², days 1, 4, 8 and 11; Doxorubicin 9 mg/m² IV, days 1-4; Dexamethasone 20 mg/d, orally, days 1-4, 9-12 and 17-20) or 3 cycles VCD (BTZ 1.3 mg/m², days 1, 4, 8 and 11; Cyclophosphamide 900 mg/m²IV; day 1, Dexamethasone 40 mg/d, orally, days 1-2, 4-5, 8-9 and 11-12) for induction therapy. In the MM5 trial, induction therapy is followed by stem cell mobilization and harvest, high-dose therapy and Lenalidomide-based consolidation/maintenance therapy. Primary end points of the ongoing study are response to treatment after induction therapy and progression-free survival. Due to improved AE profile of SC compared to IV BTZ reported by Moreau, the administration of BTZ was changed from IV to SC in 02/2012. Therefore, we were able to perform an explorative analysis of 598 patients who received at least one dose of trial medication (PAd: n=150 IV / 140 SC; VCD: n=154 IV / 140 SC). 14 patients were excluded from the analysis because administration of BTZ was changed after start of induction therapy. We analyzed whether the route of administration influenced the applied cumulative BTZ dose, toxicity and efficacy of PAd and VCD.

Results:

The cumulative applied BTZ dose was significantly higher in patients treated with SC BTZ (PAd: 28.9 mg; VCD: 28.8 mg) compared to IV-treated patients (PAd: 27.6 mg; VCD: 27.9 mg; p = 0.007). Analysis of reported AEs associated to induction therapy revealed a significantly higher rate in patients treated with IV BTZ (65.1%) compared to SC-treated patients (55.7%, p = 0.02). AE > °II were reported more frequently in the IV group (IV: 52.0%; SC: 43.9%, p = 0.004). In detail, abnormal laboratory findings including leucopenia and thrombocytopenia (IV: 23.0%; SC: 16.4%, p = 0.05), metabolism and nutrition disorders (IV: 12.5%; SC: 5.4%, p = 0.004) and gastrointestinal disorders (IV: 9.9%; SC: 3.9%, p = 0.006) occurred more often in IV-treated patients. Analysis of peripheral neuropathy (PN) ≥ °II revealed no significant differences between IV and SC BTZ during the first two cycles of induction therapy (cycle 1: IV: 1.6%; SC: 2.5%; cycle 2: IV: 2.3%; SC: 3.6%) but PN occurred more often in IV-treated patients during the third cycle of induction therapy compared to the SC group (IV: 7.6%; SC: 1.8%, p = 0.001). Overall response rates (partial response or better) were not influenced by the route of administration in patients treated with PAd (IV: 72.7%; SC: 70.7%; p = 0.79) or VCD (IV: 77.9%; SC: 82.1%; p = 0.39). Analysis of the VCD arm showed that rates of VGPR or better were significantly higher in patients treated with IV BTZ compared to SC-treated patients (IV: 41.6%; SC: 28.6%, p = 0.02). Rates of VGPR or better were also higher for IV-treated patients in the PAd arm but did not reach statistical significance (IV: 36.7%; SC: 31.4%, p=0.39). Patient characteristics including baseline creatinine levels > 2 mg/dl, obesity or age at inclusion > 65 years did not influence efficacy of IV or SC BTZ in both arms.

Conclusion:

Last year we reported on the favorable toxicity profile and equal efficacy of VCD compared to PAd. With the current analysis we demonstrate that toxicity is further reduced with SC BTZ compared to IV. We therefore recommend VCD as induction therapy. However, we show for the first time a possible loss of efficacy in SC-treated patients. Therefore it remains unclear whether the reduced toxicity justifies the general application of SC BTZ in newly diagnosed, transplant-eligible patients or whether a prolonged treatment (4 x VCD SC) may reduce toxicity while achieving similar efficacy. Further studies are warranted since our results are partially in contrast with the previously presented data in relapsed MM and the ongoing MM5 trial was initially not designed to prospectively investigate the effect of SC or IV BTZ.