Phenotypic High-Risk Disease in the Context of Carfilzomib and Lenalidomide Combination Induction Therapy for Newly Diagnosed Transplant-Eligible Myeloma Patients

Introduction

Despite efficacious modern induction combination therapies a subset of myeloma patients have high-risk disease which manifests as either primary refractory disease or early relapse following initial response. The presence of known molecular high-risk lesions explain the majority of these cases but understanding the factors influencing the poor phenotypic outcome for the remainder will help us improve outcomes further. This exploratory analysis of the Myeloma XI+ trial aimed to understand the population of patients with phenotypic high-disease in the context of carfilzomib and lenalidomide induction therapy.

Methods

The UK NCRI Myeloma XI trial is a phase III randomised controlled trial that recruited 2568 newly diagnosed transplant eligible patients, of which 526 were randomised to receive the induction combination KRdc comprising carfilzomib (K, 36mg/m2 IV d1-2, 8-9,15-16 (20mg/m2 #1d1-2)), lenalidomide (R, 25mg PO d1-21), dexamethasone (d, 40mg PO d1-4,8-9,15-16) and cyclophosphamide (c, 500mg PO d1,8) as part of an adaptive trial design. Induction therapy was planned for a minimum of 4 cycles or to maximum response prior to autologous stem cell transplant (ASCT). There was a subsequent randomisation to lenalidomide maintenance or observation at 3 months post ASCT.

Primary refractory disease was defined as not achieving at least a minimal response (MR) at maximum response after at least 4 cycles of induction therapy or progression at any time during induction regardless of initial response. Early relapse (ER) after ASCT was defined as progression within 12 months of ASCT. Molecular risk was defined as the presence of one (high risk) or more than one (ultra-high risk) of the following lesions: del(17p), gain(1q), t(4,14), t(14;16) or t(14;20).

Results

The incidence of primary refractory disease with the KRdc combination was very low. Only 8/526 (1.5%) patients were primary refractory, all having progression during induction therapy with a median progression free survival of only 126 days. The number of patients is too small to draw any firm conclusions regarding the characteristics associated with primary refractory disease.

401/526 (76%) of patients underwent high dose melphalan and ASCT on trial after KRdc induction. Those that did not proceed to ASCT on trial were either ineligible, mostly due to not completing the minimum required induction therapy, or were deemed not fit to undergo the procedure based on patient/clinician decision. Of those patients who underwent ASCT, 36/401 (9.0%) relapsed within 12 months (ER). These ER patients had both a shorter PFS2 and second PFS suggesting a continued association with adverse outcome beyond first line therapy.

Patients in the ER group were compared with those patients not relapsing until beyond 12 months after ASCT (nER). There was no difference in the sex, age or paraprotein or light chain sub-type of patients. There was evidence of a greater impact of bone marrow disease burden in the ER group with a lower haemoglobin (median 99 g/L vs 115, p = 0.0216), lymphocyte count (1.3 x10^9/L vs 1.8, p = 0.0012) and platelet count (187 x10^9/L vs 252, p = 0.0049) at baseline. Median bone marrow aspirate plasma cell infiltration was ER 33% vs nER 23%. There were no significant differences in ISS stage (ER ISS I 19%, II 50%, III 22%, nER ISS I 35%, II 36%, III 22%, p = 0.1434), lactate dehydrogenase, albumin or beta-2 microglobulin.

Patients in the ER group were less likely to have received lenalidomide maintenance (ER 12/36 [33%] vs nER 222/365 [61%]). For some (4/36) not receiving lenalidomide was due to relapse occurring prior to reaching the maintenance randomisation point (100 days post-ASCT). For those with available data 75% of patients in the ER group had molecular high (50%) or ultra-high (25%) risk disease, whilst 25% had standard risk using the trial definition. The individual lesions accounting for high-risk status were: gain(1q) in ER 42% vs nER 35%; t(4;14) ER 50% vs nER 10%; del(17p) ER 8% vs nER 7%.

Discussion

The combination of a second-generation immunomodulatory agent and proteasome inhibitor in the KRdc induction regimen is associated with deep responses and only a very small proportion of patients have primary refractory disease. Early relapse after KRdc and ASCT occurred in 9% of patients and was associated with high bone marrow disease burden and molecular high-risk features.