Intensive Versus Double Intensive Therapy in Untreated Multiple Myeloma: Updated Analysis of the Randomized Phase III Study HOVON 24 MM.
Authors: Sonneveld Pieter , van der Holt Bronno , Segeren Christine , Vellenga Edo , Raymakers Reinier , Verhoef Gregor , Schaafsma Ron , van Oers Marinus , Weijermans Pierre , Fibbe Wim , Wittebol Shulamit , van Marwijk Marinus , Biesma Douwe , Baars Joke , Schouten Harry , Westveer Petra , Steijaert Monique , Lokhorst Henk 
Published: October 2019

In 1995 HOVON started a prospective randomized multicenter trial to compare the efficacy of intensified treatment followed by myelo-ablative therapy and stem cell transplantation (PBSCT) with intensified treatment alone in patients with myeloma. We now report the results of a second analysis in 441 eligible patients with stage II (22%) and III (78%) disease. The median age was 55 years. Remission induction consisted of 3 courses of VAD. 63 patients with an HLA identical sibling were candidates for an allogeneic transplantation. After VAD, patients without donor were randomized to melphalan 140 mg/m2 divided in 2 doses of 70 mg/m2 (IDM) without PBSCT (arm A) or this regimen followed by myelo-ablation with cyclophosphamide (120 mg/kg) and TBI with PBSCT (arm B). Peripheral stem cells were mobilized by cyclophosphamide and G-CSF after VAD. Interferon-a -2a was given as maintenance therapy in both arms.

Of 441 patients, 303 were eligible for randomization. Patient characteristics were not significantly different between the two arms. The median follow-up from randomization was 56 months. 81% of patients received both cycles of IDM (79% in arm A and 83% in arm B) and 79% of patients received myeloablative therapy followed by autologous PBSCT in arm B. The median duration of maintenance treatment was 12 (arm A) vs 7 months (arm B). The CR rate was better in Arm B (28% vs 13% , p=0.002), while overall response rate (PR + CR) was not different (90% vs 86% , p=0.23). Median event-free survival (EFS) from randomization was 22 (arm B) vs 20 months (arm A) (logrank p=0.016). Median progression-free survival (PFS) was significantly better in patients treated with double intensification (24 vs 23 months, logrank p=0.036). Time to Progression (TTP) was significantly worse in arm A (median 25 vs 33 months, logrank p=0.001). The difference for EFS, PFS and TTP became only evident after at least 4 years of follow-up. Overall survival (OS) was not different (55 months in arm A vs 50 in arm B, logrank p=0.38). Multivariate analysis showed that treatment arm A, higher age, hemoglobin < 6.21 mmol/l, stage 3 and elevated serum LDH were significant adverse prognostic factors for EFS. Cytogenetic analysis, available in 151 registered patients was abnormal in 37% (45% del 13/13q-, 51% abnormal 1p/q, 33% del 6q, 89% complex abnormalities). Cox regression analysis showed that 1p/q was an independent unfavourable prognostic factor for OS, EFS, PFS and TTP (p<0.001), calculated from start VAD. Del 13/13q- was highly correlated with 1p/q abnormalities. By combining B2M > 3 mg/L with del13/13q- and 1p/q, prognostic groups could be defined with a significant impact on OS (p<0.000002), EFS (p< 0.0002), PFS (p <0.00006) and TTP (p<0.0000002). Quality of Life analysis showed significant improvement of disease-related variables in double intensive treatment.

In conclusion, in this trial second intensification by myeloablative treatment with cyclophosphamide/TBI when added to intensified chemotherapy alone resulted in a superior EFS, PFS and TTP, but not OS. The results of this trial indicate that double intensive treatment results in superior outcome, but not cure in multiple myeloma.