Acute lymphoblastic leukaemia-type intensive chemotherapy to eliminate minimal residual disease after high-dose melphalan and autologous transplantation in multiple myeloma - a phase I/II feasibility and tolerance study of 17 patients

The Role of Minimal Residual Disease Testing in Myeloma Treatment Selection and Drug Development: Current Value and Future Applications

Treatment of myeloma has benefited from the introduction of more effective and better tolerated agents, improvements in supportive care, better understanding of disease biology, revision of diagnostic criteria, and new sensitive and specific tools for disease prognostication and management. Assessment of minimal residual disease (MRD) in response to therapy is one of these tools, as longer progression-free survival (PFS) is seen consistently among patients who have achieved MRD negativity. Current therapies lead to unprecedented frequency and depth of response, and next-generation flow and sequencing methods to measure MRD in bone marrow are in use and being developed with sensitivities in the range of 10^-5 to 10^-6 cells. These technologies may be combined with functional imaging to detect MRD outside of bone marrow. Moreover, immune profiling methods are being developed to better understand the immune environment in myeloma and response to immunomodulatory agents while methods for molecular profiling of myeloma cells and circulating DNA in blood are also emerging. With the continued development and standardization of these methodologies, MRD has high potential for use in gaining new drug approvals in myeloma. The FDA has outlined two pathways by which MRD could be qualified as a surrogate endpoint for clinical studies directed at obtaining accelerated approval for new myeloma drugs. Most importantly, better understanding of MRD should also contribute to better treatment monitoring. Potentially, MRD status could be used as a prognostic factor for making treatment decisions and for informing timing of therapeutic interventions. Clin Cancer Res; 23(15); 3980-93. ©2017 AACR.

Role of MRD status in relation to clinical outcomes in newly diagnosed multiple myeloma patients: a meta-analysis

Driven by access to better drugs, on average, newly diagnosed multiple myeloma patients have over 10 years overall survival. Using modern combination therapies – with or without the addition of high-dose melphalan and autologous stem cell transplantation – up to 80% of patients reach a complete response. As a logical and necessary step forward, clinical studies have explored strategies to detect minimal residual disease (MRD) and its correlation with clinical outcomes. In this context, MRD has been proposed as a regulatory endpoint for drug approval in newly diagnosed multiple myeloma. To better define the role of MRD negativity in relation to clinical outcomes, we undertook a meta-analysis including published clinical trials of newly diagnosed multiple myeloma patients. We applied a random effects model which weighted studies using the inverse-variance method. Studies were combined on the scale of the logarithm of the hazard ratio (HR) and the corresponding standard error. We found that remaining MRD positive was associated with worse progression-free survival (HR=2.85; 95% confidence interval (CI) 2.17–3.74; P<0.001) and overall survival (HR=2.08; 95% CI 1.44–3.01; P<0.001). Our results show that MRD negativity is a strong predictor of clinical outcomes, supportive of MRD becoming a regulatory endpoint for drug approval in newly diagnosed multiple myeloma.

High-dose chemotherapy and autologous hematopoietic stem cell transplantation in myeloma patients under the age of 65 years

One or two cycles of high-dose chemotherapy with autologous hematopoietic stem cell transplantation have been shown to improve response rates and survival in myeloma. While this observation has largely been made in patients under the age of 65 years, there is evidence to suggest that the conclusions can be extrapolated to older individuals as well. In contrast to other hematologic malignancies treated with high-dose therapy, autografted myeloma patients continue to relapse several years after transplantation, and few patients are cured with this modality. However, up to a third of patients may be alive beyond a decade; some with excellent quality of life giving rise to the concept of 'operational cure'. Relapsing disease can be treated with novel agents or repeat high-dose chemotherapy and transplantation. The pressing questions to which answers are not obvious at the moment are whether tandem transplantation should be offered to all patients, and whether novel agents should be used before transplantation or reserved for relapse. Despite their excellent activity, there is no evidence so far that novel agents such as thalidomide, bortezomib and lenalidomide can replace high-dose chemotherapy and stem cell transplantation.

Response to induction chemotherapy is not essential to obtain survival benefit from high-dose melphalan and autotransplantation in myeloma

Two hundred and twenty-two myeloma patients autografted after 200 mg/m(2)melphalan were studied to examine the relationship between response to induction chemotherapy and outcome. Induction comprised cyclophosphamide, vincristine, doxorubicin and methylprednisolone (C-VAMP) every 3 weeks for one cycle beyond maximum response. 81% responded to C-VAMP (chemosensitive) with 40 complete (CR) and 139 partial (PR) remissions, and 43 did not respond (NR; <50% reduction in paraprotein; primary refractory). Overall, 130 patients (59%) attained or remained in CR post-transplant; including 40% of NR, 53% of PR, and 97% of CR after C-VAMP (P < 0.0001). Amongst these 130 patients, the 5-year OS was independent of response to C-VAMP (NR 79%, PR 74%, CR 60%; P = 0.69). Similarly, among the 69 patients in PR post-transplant, the 5-year OS was independent of response to C-VAMP. In Cox analysis, lack of response to C-VAMP did not affect outcome significantly. These data show that lack of response to induction therapy does not automatically predict poor long-term outcome in myeloma, since a substantial proportion of these patients attain CR after autograft and enjoy extended survival. Myeloma patients should not be disqualified from an autograft based upon lack of response to induction chemotherapy.

Some early phase II trials in previously untreated multiple myeloma: The Royal Marsden experience

Multiple myeloma is at a stage today where acute leukemia was in the 1960s and 1970s when the aim was to attain complete remission (CR), which would translate into prolonged overall survival (OS) and a cure. The Royal Marsden group was the first to establish a dose-response effect for melphalan leading to CR in patients with myeloma. Since then, different strategies have been developed to improve the results of high-dose therapy, including alternating conditioning regimens, peripheral blood stem cells (PBSC) as a source of stem cells, purging techniques to decrease graft contamination by the myeloma cell, increased dose intensity by means of tandem transplants, and finally, allogeneic matched or unmatched stem cell transplantation. Components of treatment offered at Royal Marsden since 1980 are upfront high-dose melphalan (HDM) 140 mg/m(2), induction infusional chemotherapy followed by consolidation with HDM with autotransplantation, and maintenance with interferon-alpha2b (IFN) (collectively termed sequential therapy). Each of these components has shown benefits in selected studies and together they have dramatically improved the outlook for patients with myeloma.