Determination of Minimal Residual Disease in Multiple Myeloma: Does It Matter?

Lumbar MR-based radiomics nomogram for detecting minimal residual disease in patients with multiple myeloma

OBJECTIVES

Minimal residual disease (MRD) is a standard for assessing treatment response in multiple myeloma (MM). MRD negativity is considered to be the most powerful predictor of long-term good outcomes. This study aimed to develop and validate a radiomics nomogram based on magnetic resonance imaging (MRI) of the lumbar spine to detect MRD after MM treatment.

METHODS

A total of 130 MM patients (55 MRD negative and 75 MRD positive) who had undergone MRD testing through next-generation flow cytometry were divided into a training set (n = 90) and a test set (n = 40). Radiomics features were extracted from lumbar spinal MRI (T1-weighted images and fat-suppressed T2-weighted images) by means of the minimum redundancy maximum relevance method and the least absolute shrinkage and selection operator algorithm. A radiomics signature model was constructed. A clinical model was established using demographic features. A radiomics nomogram incorporating the radiomics signature and independent clinical factor was developed using multivariate logistic regression analysis.

RESULTS

Sixteen features were used to establish the radiomics signature. The radiomics nomogram included the radiomics signature and the independent clinical factor (free light chain ratio) and showed good performance in detecting the MRD status (area under the curve: 0.980 in the training set and 0.903 in the test set).

CONCLUSIONS

The lumbar MRI-based radiomics nomogram showed good performance in detecting MRD status in MM patients after treatment, and it is helpful for clinical decision-making.

KEY POINTS

• The presence or absence of minimal residual disease status has a strong predictive significance for the prognosis of patients with multiple myeloma. • A radiomics nomogram based on lumbar MRI is a potential and reliable tool for evaluating minimal residual disease status in MM.

Future Directions in Maintenance Therapy in Multiple Myeloma

Autologous stem cell transplantation (ASCT) has been a backbone of therapy for newly diagnosed patients with multiple myeloma eligible for high-dose therapy for decades. Survival outcomes have continued to improve over time, in part because of the incorporation of highly effective induction regimens prior to ASCT as well as post-ASCT maintenance therapy. Randomized phase III clinical trials have helped establish lenalidomide maintenance as a standard of care. However, as nearly all patients will eventually experience disease relapse, there continues to be significant interest in developing novel maintenance strategies to improve upon lenalidomide maintenance. In this review, we summarize the available evidence for the use of immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies as post-ASCT maintenance therapies as well as discuss future directions and unanswered questions in the field.

Evolution of Treatment Paradigms in Newly Diagnosed Multiple Myeloma

The plasma cell neoplasm multiple myeloma (MM) is currently considered incurable. However, significant advances in treatment options over the past 20 years have led to unprecedented response rates to initial therapy as well as prolonged survival rates. Induction regimens have evolved from alkylator-based therapies to those consisting of immunomodulatory drugs and proteasome inhibitors. The combination of bortezomib/lenalidomide/dexamethasone (VRd) has emerged as a standard regimen for both transplant-eligible (TE) and transplant-ineligible (TI) patient populations. More recent efforts have focused on the incorporation of monoclonal antibody therapy into the newly diagnosed setting, particularly anti-CD38 monoclonal antibodies. In the TI patient population, the combination of daratumumab/lenalidomide/dexamethasone is now considered another standard therapy. In the TE setting, it remains to be determined whether the addition of daratumumab to the VRd backbone results in improved long-term outcomes. Recent studies have confirmed the progression-free survival benefit of upfront autologous stem cell transplant and have established lenalidomide maintenance as a standard of care. Multiple studies are evaluating whether inclusion of monoclonal antibody therapy in the maintenance setting will improve outcomes. The optimal management of newly diagnosed patients with high-risk cytogenetics remains to be determined. We discuss the emerging therapies that will likely shape management of newly diagnosed MM in the future.

The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of multiple myeloma

Outcomes in multiple myeloma (MM) have improved dramatically in the last two decades with the advent of novel therapies including immunomodulatory agents (IMiDs), proteasome inhibitors and monoclonal antibodies. In recent years, immunotherapy for the treatment of MM has advanced rapidly, with the approval of new targeted agents and monoclonal antibodies directed against myeloma cell-surface antigens, as well as maturing data from late stage trials of chimeric antigen receptor CAR T cells. Therapies that engage the immune system to treat myeloma offer significant clinical benefits with durable responses and manageable toxicity profiles, however, the appropriate use of these immunotherapy agents can present unique challenges for practicing physicians. Therefore, the Society for Immunotherapy of Cancer convened an expert panel, which met to consider the current role of approved and emerging immunotherapy agents in MM and provide guidance to the oncology community by developing consensus recommendations. As immunotherapy evolves as a therapeutic option for the treatment of MM, these guidelines will be updated.

Statistics and measurable residual disease (MRD) testing: uses and abuses in hematopoietic cell transplantation

SERIES EDITORS' NOTE

The decision whether to recommend a transplant to someone with acute leukemia in first remission is complex and challenging. Diverse, often confounded co-variates interact to influence one's recommendation. Briefly, the decision metric can be viewed in three spheres: (1) subject-; (2) transplant-; and (3) disease-related co-variates. Subject-related co-variates include items such as age and comorbidities. Transplant-related co-variates include items such as donor-types, graft source, proposed conditioning and pre- and post-transplant immune suppression.But what of disease-related variables? Previously haematologists relied on co-variates such as WBC at diagnosis, chemotherapy cycles to achieve first remission, cytogenetics and most recently, mutation topography. However, these co-variates have largely been replaced by results of measurable residual disease (MRD)-testing. Many chemotherapy-only and transplant studies report strong correlations between results of MRD-testing on therapy outcomes such as cumulative incidence of relapse (CIR), leukemia-free survival (LFS) or survival. (CIR makes biological sense in a transplant context whereas LFS and survival do not give competing causes of death such as transplant-related mortality (TRM), graft-versus-host disease and interstitial pneumonia unrelated to relapse probability).This raises the question of how useful results are of MRD-testing in predicting CIR after transplants. Elsewhere we discussed accuracy and precision of MRD-testing in predicting outcomes of therapy of acute myeloid leukemia (Estey E, Gale RP. Leukemia 31:1255-1258, 2017; Hourigan CS, Gale RP, Gormley NJ, Ossenkoppele GJ, Walter RB. Leukemia 31:1482-1490, 2017). Briefly put, not terribly good. Although results of MRD-testing are often the most powerful predictor of CIR in multivariable analyses, the C-statistic (a measure of prediction accuracy) is often only about 0.75. This is much better than flipping a fair coin but far from ideal.In the typescript which follows, Othus and colleagues discuss statistical issues underlying MRD-testing in the context of haematopoietic cell transplants. We hope readers, especially haematologists who often need to make transplant recommendations to people with acute leukemia in first remission, will read it carefully and critically. The bottom line is MRD-test data are useful but considerable uncertainty is unavoidable with substantial false-positive and -negative rates. We need to acknowledge this uncertainty to ourselves and to the people we counsel. The authors quote Voltaire who said: Doubt is not a pleasant condition, but certainty is an absurd one. Sadly so, but we do the best we can. Robert Peter Gale, Imperial College London, and Mei-Jie Zhang, Medical College of Wisconsin and CIBMTR.