Bortezomib Induction and Maintenance in Patients with Newly Diagnosed Multiple Myeloma: Long-Term Follow-up of the HOVON-65/GMMG-HD4 Trial

Background: We reported better PFS and OS in transplant eligible patients with newly diagnosed Multiple Myeloma (MM) who were treated with bortezomib during induction and maintenance, when compared with standard treatment in the HOVON-65/GMMG-HD4 trial. (P. Sonneveld et al., J Clin Oncol 30:2946-2955, 2012). Here the long-term follow up data are presented.

Methods: 827 eligible patients were randomized to induction therapy with VAD (vincristine, doxorubicin, dexamethasone) or PAD (bortezomib, doxorubicin, dexamethasone) followed by high-dose melphalan (once or twice) and autologous stem cell transplant. Maintenance consisted of daily thalidomide (T) 50 mg (VAD arm) or 2-weekly bortezomib (B) 1.3 mg/m² (PAD arm) for 2 years. The primary endpoint was progression-free survival (PFS) adjusted for ISS stage.

Results: After a median follow up of 91.4 months (maximum 119) 410 patients are alive. Response rates were VAD/HDM/T: CR 25%, ≥VGPR 56%, ≥PR 83%; PAD/HDM/B: CR 37%, ≥VGPR 76%%, ≥PR 91%, The median duration of maintenance therapy was 14 months (thalidomide) and 23 months (bortezomib), respectively. Main reasons for discontinuation were toxicity (T: 31%; B: 11%), disease progression (T: 33%; B: 36%) or normal completion (T: 28%; B: 48%).

Of 827 patients in the analysis, 206 are alive without progression/relapse. PFS was significantly better in the bortezomib arm, i.e. median 34 versus 28 months (HR=0.77, 95% CI=0.65-0.90, p=0.001). Median overall survival (OS) was 90 months in the bortezomib arm vs 83 months in the control arm, but 42% at 9 years in both arms. We used the restricted mean survival time (RMST) method to compare OS between the two treatment arms In univariate analysis. The difference in RMST_8y was 4.8 months (95% CI 0.2-9.5, p=0.04) in favor of the bortezomib arm.

A landmark analysis in patients who had received HDM starting at 12 months showed a significant PFS advantage of bortezomib in all patients (p=0.02), in patients in VGPR/PR (p=0.02) but not in CR (p=0.19). For OS there was no advantage for bortezomib in either group.

PFS at 60 months in bortezomib treated patients was not different when single vs double HDM/ASCT was administered, i.e. 28% vs 27%. However, OS at 60 months was 71% vs 60% in favor of double HDM/ASCT (p=0.04). Subgroup analysis was performed based on presence/absence of adverse FISH (CA) in 395 patients treated with double HDM/ASCT. PFS at 60 months for each abnormality (CA or no CA) in bortezomib vs standard arm is given in Table 1

These data show that bortezomib treatment combined with double HDM/ASCT significantly improves PFS and OS in patients with del(17p) and almost abrogates the negative impact of this CA. In t(4;14) and add(1q) some improvement is observed, however the negative impact remains significant. In high-risk patients presenting with elevated creatinine >2 mg/dL bortezomib significantly improved PFS at 60 months (32% vs 5%) (p=0.001) and OS at 60 months (66% vs 21% months (p<0.001)). OS at 8 years was 46% vs 12%. Finally, OS from progression/relapse was not different between patients treated in the bortezomib vs standard arm (OS at 72 months: 33% vs 35%, p=0.73)

Conclusions: We conclude that bortezomib leads to a significant and lasting improvement of PFS and OS. Bortezomib significantly reduces the high-risk impact of del(17p) and renal impairment on survival.

This trial was registered as NTR213; EudraCT no. 2004-000944-26.and supported by the Dutch Cancer Foundation, the German Federal Ministry of Education and Research and an unrestricted grant from Janssen. The GMMG group received grants for this trial by Novartis, AMGEN, Chugai and Roche.