Outcomes after biochemical or clinical progression in patients with multiple myeloma.

Almost all patients with multiple myeloma (MM) eventually relapse, either asymptomatically or with end-organ damage. However, it remains unclear whether initiating therapy at the time of biochemical progression (BP) improves the outcomes compared with initiating therapy at the clinical progression (CP) stage. Here, we retrospectively assessed 1347 patients with relapsed MM. Most progressions were BP (60.4%); 39.6% had CP. The most prevalent symptoms at relapse were new or evolving bone disease (80.9%), anemia (38.0%), and renal failure (12.7%). Patients with BP had longer median time from second-line treatment to the next treatment compared with patients who had CP (17.0 vs 9.6 months; P < .001) as well as longer median overall survival from first relapse (59.4 vs 26.2 months; P < .001). Male sex (odds ratio [OR], 1.49; 95% confidence interval [CI], 1.02-2.18; P = .04), plasma cell labeling index ≥2% (OR, 1.58; 95% CI, 1.02-2.45; P = .04), and extramedullary disease at diagnosis (OR, 1.84; 95% CI, 1.08-3.13; P = .03) were associated with higher risk of CP, whereas very good partial remission or better had decreased risk of CP (OR, 0.62; 95% CI, 0.43-0.91; P = .02). To conclude, patients with CP have inferior postprogression outcomes compared with patients who have BP. Patients with deeper response to first-line therapy are less likely to develop CP. The presence of a specific CRAB (C, hypercalcemia; R, renal failure; A, anemia; B, bone disease) symptom at diagnosis predicts for the development of similar CRAB symptoms at relapse.

Sarcopenia identified by computed tomography imaging using a deep learning-based segmentation approach impacts survival in patients with newly diagnosed multiple myeloma.

BACKGROUND: Sarcopenia increases with age and is associated with poor survival outcomes in patients with cancer. By using a deep learning-based segmentation approach, clinical computed tomography (CT) images of the abdomen of patients with newly diagnosed multiple myeloma (NDMM) were reviewed to determine whether the presence of sarcopenia had any prognostic value. METHODS: Sarcopenia was detected by accurate segmentation and measurement of the skeletal muscle components present at the level of the L3 vertebrae. These skeletal muscle measurements were further normalized by the height of the patient to obtain the skeletal muscle index for each patient to classify them as sarcopenic or not. RESULTS: The study cohort consisted of 322 patients of which 67 (28%) were categorized as having high risk (HR) fluorescence in situ hybridization (FISH) cytogenetics. A total of 171 (53%) patients were sarcopenic based on their peri-diagnosis standard-dose CT scan. The median overall survival (OS) and 2-year mortality rate for sarcopenic patients was 44 months and 40% compared to 90 months and 18% for those not sarcopenic, respectively (p < .0001 for both comparisons). In a multivariable model, the adverse prognostic impact of sarcopenia was independent of International Staging System stage, age, and HR FISH cytogenetics. CONCLUSIONS: Sarcopenia identified by a machine learning-based convolutional neural network algorithm significantly affects OS in patients with NDMM. Future studies using this machine learning-based methodology of assessing sarcopenia in larger prospective clinical trials are required to validate these findings.

Deepening Responses after Upfront Autologous Stem Cell Transplantation in Patients with Newly Diagnosed Multiple Myeloma in the Era of Novel Agent Induction Therapy.

High-dose melphalan followed by autologous stem cell transplantation (ASCT) remains the standard of care for transplant-eligible patients with newly diagnosed multiple myeloma (NDMM). Achievement of complete response (CR) and minimal residual disease (MRD) negativity are associated with improved progression-free survival (PFS) and overall survival (OS). With superior triplet- and quadruplet-based induction regimens, a higher proportion of patients are achieving deep responses of at least a very good partial response (VGPR) or better. The probability of achieving different levels of deeper hematologic responses post-ASCT based on the pre-ASCT depth of response is less clear in the existing literature but would be of value to patients and providers in discussing the added benefit of ASCT. We assessed the rate of deepening the hematologic response with upfront ASCT in patients with NDMM, mainly to MRD-negative CR, based on the response achieved after induction therapy. We retrospectively reviewed 210 patients with NDMM who underwent upfront ASCT at Mayo Clinic Rochester between May 1, 2018, and July 31, 2019. In addition to the availability of next-generation flow cytometry (NGF) testing for MRD status, which yielded a sensitivity of 10-5, the more sensitive mass spectrometry-based assessment of peripheral blood (ie, MASS-FIX) for monoclonal proteins was used rather than conventional immunofixation. Pre-ASCT, 23 patients (11%) achieved MRD-negative CR, which increased to 66 patients (31%) post-ASCT. Of 187 patients not in MRD-negative CR pre-ASCT, 45 (24%) converted to MRD-negative CR. Patients with MRD-positive CR before ASCT had the highest rates of conversion to MRD-negative CR. HR cytogenetics did not impact rates of MRD-negative CR achievement post-ASCT irrespective of pre-ASCT IMWG response (P = 1.0). Overall, irrespective of IMWG response, 43 patients (20%) were MRD-negative pre-ASCT (19 in VGPR, 24 in CR or sCR), and 102 patients (49%) were MRD-negative post-ASCT (36 in VGPR, 66 in CR or sCR). Among 85 patients with VGPR post-ASCT, 36 achieved MRD negativity, of whom 8 (22%) progressed, whereas 49 had MRD-positive disease, of whom 24 (49%) progressed (P = .014). Upfront ASCT in patients with NDMM led to deeper responses, with 24% converting to MRD negative CR and more than doubling of the total rate of MRD negativity irrespective of IMWG response depth.

Hypovitaminosis D Is Prevalent in Patients With Renal AL Amyloidosis and Associated With Renal Outcome.

Introduction: Vitamin D deficiency is common, but no data have been reported on vitamin D levels in light chain (AL) amyloidosis. Patients and Methods: In this exploratory study, stored serum samples from 173 patients with newly diagnosed AL amyloidosis were analyzed for vitamin studies which included 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D] and vitamin D binding protein (DBP). Measurements were made by liquid chromatography-tandem mass spectrometry. Kidney survival and overall survival (OS) were assessed in association to vitamin D status. Results: Cardiac and kidney involvement occurred in 69% and 63% of patients, respectively. 25(OH)D deficiency (<20 ng/mL) was seen in 56.6% of the patients and was notably found among patients with heavy proteinuria (96%), hypoalbuminemia (84.3%) and morbidly obese patients (68.3%). Heavy proteinuria (>5 gr/24-h) and vitamin D supplementation were independent predictors of 25(OH)D level on nominal multivariate regression analysis. 1,25(0H)2D deficiency was noted in 37.6% of patients and was independently associated with low eGFR and hypoalbuminemia. Progression to ESRD occurred in 23.7% of evaluable patients. Patients who progressed to ESRD had lower serum 25(OH)D and 1,25(OH)2D levels compared to those who did not progress to ESRD. On a multivariate analysis, severe 25(OH)D deficiency was an independent predictor of progression to ESRD as was renal stage, while 1,25(OH)2D deficiency was not. Conclusions: Hypovitaminosis D is common in AL amyloidosis, particularly among patients with heavy proteinuria. Severe 25(OH)D deficiency at time of diagnosis predicts progression to ESRD.

Phase 2 trial of ixazomib, cyclophosphamide, and dexamethasone for previously untreated light chain amyloidosis.

Bortezomib, a proteasome inhibitor (PI), has shown efficacy in the treatment of newly diagnosed and relapsed light chain (AL) amyloidosis, and is often used in combination with cyclophosphamide and dexamethasone. Ixazomib is the first oral PI to be approved in routine practice but has not yet been evaluated in the upfront treatment setting. Newly diagnosed AL amyloidosis patients with measurable disease and adequate organ function were enrolled. The primary objective was to determine the hematologic response rate of ixazomib in combination with cyclophosphamide and dexamethasone. Treatment was given for 12 cycles, followed by ixazomib maintenance until progression. Thirty-five patients were included; their median age was 67 years, and 69% were male. Major organ involvement included heart (66%) and kidneys (54%). A median of 4 induction cycles (range, 1-12) were administered. The overall hematologic response to induction was 63% and included complete response in 11.4% and very good partial response in 37.1% of patients. One patient was upstaged to complete response during maintenance. The most common reason for going off study was the institution of alternate therapy (61%). With a median follow-up of 29.7 months for the living patients, the 2-year progression-free survival and overall survival were 74% and 78%, respectively. The median time to alternate therapy was 7.5 months. Grade ≥3 hematologic and nonhematologic adverse events occurred in 23% and 49% of patients. Given ixazomib's favorable toxicity profile, which is an important advantage for the typically frail AL population, further evaluation of ixazomib in other combinations in the upfront setting is warranted. This trial was registered at www.clinicaltrials.gov as #NCT01864018.

Prognostic significance of acquired 1q22 gain in multiple myeloma.

Gain of 1q22 at diagnosis portends poorer outcomes in multiple myeloma (MM), but the prognostic significance of acquired 1q22 gain is unknown. We identified 63 MM patients seen at Mayo Clinic from 1/2004 to 12/2019 without 1q22 gain at diagnosis who acquired it during follow up and compared them to 63 control patients who did not acquire 1q22 gain with similar follow up. We also compared outcomes in the acquired 1q22 gain group with outcomes in 126 patients with 1q22 gain present at diagnosis. The incidence of acquired 1q22 gain was 6.1% (median follow-up 6.8 years); median time to acquisition was 5.0 years (range: 0.7-11.5 years). Abnormalities on baseline fluorescence in situ hybridization (FISH) included trisomies (54%) and monosomy 13 (39%); 16 (25%) had high-risk (HR) translocations or del(17p). Median progression-free survival with front line therapy was 29.5 months in patients with acquired 1q22 gain, versus 31.4 months in control patients (p = .34) and 31.2 months in patients with de novo 1q22 gain (p = .04). Median overall survival (OS) from diagnosis was 10.9 years in patients with acquired 1q22 gain, versus 13.0 years in control patients (p = .03) and 6.3 years in patients with de novo 1q22 gain (p = .01). Presence of HR FISH at baseline increased risk of 1q22 gain acquisition. We demonstrate that acquisition of 1q22 gain is a significant molecular event in MM, associated with reduced OS. Among HR patients for whom this clonal evolution is determined, a risk-adapted approach and/or clinical trial should be considered.

Mortality trends in multiple myeloma after the introduction of novel therapies in the United States.

Advances in the understanding of disease biology, drug development, and supportive care have led to improved outcomes in multiple myeloma. Given that these improvements have been reported in clinical trial and referral center populations, questions remain about the generalizability of this observation to patients treated in the community. Contrasting the overall survival experience of 3783 patients seen at Mayo Clinic and 57,654 patients followed in the Surveillance, Epidemiology, and End Results Program (SEER) between 2004 and 2018, we observed different mortality trends across patient populations and subgroups. Early mortality decreased and estimated 5-year overall survival increased over time in both patient populations. Excess mortality (compared to the general population) declined over time in Mayo Clinic patients and remained largely unchanged in SEER patients. Improvements over time were primarily observed in patients with favorable disease characteristics and older patients with multiple myeloma remain a vulnerable population with significant excess mortality compared to the United States general population. Patients with unfavorable disease characteristics have derived disproportionately less benefit from recent advances in the field. Future efforts need to focus on the development of safe and effective therapies for these patients and on increasing timely access to specialized care for patients in the community.

Treatment of AL Amyloidosis: Mayo Stratification of Myeloma and Risk-Adapted Therapy (mSMART) Consensus Statement 2020 Update.

Immunoglobulin light chain (AL) amyloidosis is a clonal plasma cell disorder leading to progressive and life-threatening organ failure. The heart and the kidneys are the most commonly involved organs, but almost any organ can be involved. Because of the nonspecific presentation, diagnosis delay is common, and many patients are diagnosed with advanced organ failure. In the era of effective therapies and improved outcomes for patients with AL amyloidosis, the importance of early recognition is further enhanced as the ability to reverse organ dysfunction is limited in those with a profound organ failure. As AL amyloidosis is an uncommon disorder and given patients' frailty and high early death rate, management of this complex condition is challenging. The treatment of AL amyloidosis is based on various anti-plasma cell therapies. These therapies are borrowed and customized from the treatment of multiple myeloma, a more common disorder. However, a growing number of phase 2/3 studies dedicated to the AL amyloidosis population are being performed, making treatment decisions more evidence-based. Supportive care is an integral part of management of AL amyloidosis because of the inherent organ dysfunction, limiting the delivery of effective therapy. This extensive review brings an updated summary on the management of AL amyloidosis, sectioned into the 3 pillars for survival improvement: early disease recognition, anti-plasma cell therapy, and supportive care.

Second Stem Cell Transplantation for Relapsed Refractory Light Chain (AL) Amyloidosis.

Autologous stem cell transplantation (ASCT) is an effective treatment modality in light chain (AL) amyloidosis but can be offered only to a subset of patients. The feasibility, benefit, and risks of second ASCT (ASCT2) have been rarely reported. The objective of this study was to assess the utility of ASCT2 in AL amyloidosis and to identify the target population with the greatest benefit. This retrospective study examined all AL patients who underwent ASCT2 for relapsed refractory disease between 2003 and 2020. Twenty-six patients were included. The use of ASCT2 has increased over time, from 2.5% of all ASCTs from 2003 to 2011 to 5% from 2012 to 2020 (P = .056). The median time between the first ASCT (ASCT1) and ASCT2 was 7.2 years (range, 0.6 to 17.7). Fifty-four percent of patients received at least one line of therapy between ASCTs. Second stem cell mobilization prior to ASCT2 was required in 42% of patients. Full-dose melphalan (200 mg/m2) was given to 73% of patients. Two patients had failed to engraft by day 100 but eventually recovered to normal blood counts. Both had second stem cell mobilization prior to ASCT2 with prior melphalan exposure. Four patients (15%) died before day 100. Progression-free and overall survival were significantly longer from ASCT2 for those who had durable remission after ASCT1 (≥5 years) and for those who did not receive therapy between ASCTs. ASCT2 is feasible and can produce favorable outcomes, especially among those with durable response to ASCT1. ASCT2, if chosen, should preferably be performed after durable response to ASCT1 and at first progression.

The Impact of Socioeconomic Risk Factors on the Survival Outcomes of Patients With Newly Diagnosed Multiple Myeloma: A Cross-analysis of a Population-based Registry and a Tertiary Care Center.

BACKGROUND: Multiple myeloma (MM) is a heterogeneous clonal plasma cell disorder leading to differences in clinical outcomes such as overall survival (OS) among patients. We hypothesized that with expensive, novel therapeutic agents and paradigm shifts to maintain continuous therapy and improvement in OS, patients with MM are subject to the pressures of financial toxicity and the need for social support, which may be of prognostic importance. MATERIALS AND METHODS: In this study, we examined the records of 122,458 patients from the National Cancer Database (NCDB) to determine the significance of socioeconomic factors such as estimated annual household income and education level, which were based on the patient's ZIP Code and the United States Census Bureau's 5-year report from 2008 to 2012. These socioeconomic factors, in addition to marital status, were then assessed individually and as a cumulative socioeconomic score for prognostic significance in a cohort of 2543 patients treated at a tertiary care center utilizing known biologic risk factors, such as cytogenetic risk, International Staging System classification, and serum lactate dehydrogenase levels. RESULTS: Only marital status and estimated annual household income at diagnosis negatively impacted OS in a univariate analysis, but not in the context of a multivariable analysis incorporating known biologic risk factors. CONCLUSION: Future analyses in other academic and non-academic centers located in urban and rural regions are required to understand the socioeconomic drivers of OS disparity among patients with MM observed nationally.

Clinical Characteristics and Outcomes of Patients With Primary Plasma Cell Leukemia in the Era of Novel Agent Therapy.

OBJECTIVE: To evaluate the clinical outcomes of patients with primary plasma cell leukemia (pPCL) defined by 5% or greater clonal circulating plasma cells on peripheral blood smear and treated with novel agent induction therapies. PATIENTS AND METHODS: A cohort of 68 patients with pPCL diagnosed at the Mayo Clinic in Rochester, Minnesota, from January 1, 2000, to December 31, 2019, and treated with novel agent induction therapies was evaluated. RESULTS: The median follow-up was 46 (95% CI, 41 to 90) months. The median bone marrow plasma cell content was 85% (range, 10% to 100%) and median clonal circulaitng plasma cell percentage on the peripheral blood smear was 26% (range, 5% to 93%). There was a preponderance of t(11;14) primary cytogenetic abnormality in this cohort. The median time to next therapy (TTNT) and overall survival (OS) for all patients with pPCL patients in this cohort was 13 (95% CI, 9 to 17) and 23 (95% CI, 19 to 38) months, respectively. However, when stratified by cytogenetic risk, the median TTNT and OS were 16 and 51 months for standard risk vs 9 and 19 months for high risk (P=.01 for OS). CONCLUSION: Primary plasma cell leukemia remains an aggressive disease with poor prognosis despite novel agent-based therapies. Some patients have better than expected survival and this phenomenon may be influenced by the absence of high-risk cytogenetics. Newer treatment regimens are needed to improve the prognosis of this devastating disease.

Outcomes with different administration schedules of bortezomib in bortezomib, lenalidomide and dexamethasone (VRd) as first-line therapy in multiple myeloma.

Induction therapy for multiple myeloma with bortezomib (Velcade), lenalidomide (Revlimid), and dexamethasone (d) (VRd) was traditionally administered as bortezomib given twice weekly on a 3 week cycle. A modified schedule of weekly bortezomib has been adopted over time to decrease treatment burden for patients and reduce treatment-emergent neuropathy. This study evaluates the response rates and outcomes with different schedules of bortezomib in VRd administered for first-line treatment for patients with newly diagnosed MM (NDMM). We retrospectively analyzed patients treated with upfront VRd from June 30th 2008 to December 31st 2018, for variations of bortezomib administration. Five hundred and fifty-five (555) NDMM patients met inclusion criteria; median age 63 years and 61% men. Bortezomib was administered twice weekly every 21 days in 43%, once weekly every 21 days in 41% and once weekly every 28 days in 16%. Though peripheral sensory neuropathy was more frequent with twice weekly dosing (P = .002), this group achieved shorter time to best response (P = .01). Weekly every 21-day treatment saw higher VGPR or better rates (P = .02). However, with median follow up time of 37 months (IQR 22-56), we found no difference in PFS or OS among the groups. While small differences in response rates were found among the varying administration schedules of bortezomib administration, there was no significant effect on PFS or OS. Given that VRd remains a first line standard of care option for newly diagnosed MM, in the absence of a large trial comparing bortezomib dosing schedule modifications, these results are helpful in supporting current practices of once weekly administration.

Correction: Bone marrow plasma cells 20% or greater discriminate presentation, response, and survival in AL amyloidosis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Refining amyloid complete hematological response: Quantitative serum free light chains superior to ratio.

Response assessment in light chain (AL) amyloidosis is based on serum and urine monoclonal protein studies. Newly diagnosed patients (n = 373) who achieved very good partial response or complete response (CR) to first line therapy were assessed for the survival impact of each of the monoclonal protein studies. At end of therapy (EOT), negative serum/urine immunofixation (IFE) was achieved in 61% of patients, 72% achieved normal serum free light chain ratio (sFLCR), and the median involved free light chain (iFLC) and difference between involved to uninvolved light chain (dFLC) were 17 mg/L and 5 mg/L, respectively. Overall, 46% of patients achieved a CR at EOT. At EOT, iFLC ≤20 mg/L and dFLC ≤10 mg/L were additive in survival discrimination to negative serum/urine IFE and were independent predictors of overall survival. In contrast, normalization of sFLCR did not add survival discrimination to serum/urine IFE and was not independent predictor of survival. We propose a new definition for hematological CR to include serum/urine IFE negativity plus iFLC ≤20 mg/L or dFLC ≤10 mg/L, instead of the current definition of serum/urine IFE negativity and normal sFLCR. Complete response using dFLC ≤10 mg/L had the best performance in those with significant renal dysfunction and by light chain isotype, making it the preferred partner to IFE. Validation of these results in a multicenter cohort is warranted.

Outcomes with early vs. deferred stem cell transplantation in light chain amyloidosis.

In the presence of effective treatment options for systemic light chain (AL) amyloidosis, autologous stem cell transplantation (ASCT) is sometimes deferred after stem cell collection. We designed this retrospective study to compare overall survival (OS) between patients who proceed directly to ASCT after stem cell collection and those who defer ASCT. We included patients with AL amyloidosis who had stem cell collection at Mayo Clinic, Minnesota, from 2004 to 2018. ASCT was considered "early" if performed within 90 days of collection, and "deferred" if performed after 90 days, or not done by last follow up. We included 651 patients; 527 underwent early ASCT and 124 deferred ASCT. There was no difference in OS with early vs. deferred ASCT (median OS: 13.0 vs. 11.4 years, respectively, P = 0.28). There was no difference in OS between the 2 groups among patients with early or advanced Mayo Stage. Among patients who achieved ≥very good partial response at the time of collection, OS in the early and deferred groups was 14.2 and 13.4 years, respectively (P = 0.06). Survival outcomes are similar with early and deferred ASCT. Further studies are needed to identify patients who would benefit from each approach.

The role of bone marrow biopsy in patients with plasma cell disorders: should all patients with a monoclonal protein be biopsied?

We conducted a retrospective review of multiple myeloma (MM), smoldering multiple myeloma (SMM), and monoclonal gammopathy of undetermined significance (MGUS) patients seen at Mayo Clinic to determine whether a bone marrow biopsy (BM) is necessary in all patients diagnosed with a monoclonal protein. A total of 2254 MM, 397 SMM, and 5836 MGUS patients were included in the study. A total of 29 (1.3%) MM patients "without CRAB/FLC" were identified where BM or advanced imaging was critical for diagnosis, 8 (0.3% MM cohort) of whom were diagnosed with MM solely on BM findings (plasma cells > 60%). Without BM or advanced imaging none of these patients would be classified low-risk MGUS. A total of 314 (79%) MGUS-like SMM patients were identified where classification of SMM was based on BM findings. Without BM 97 would be classified as low/low-intermediate-risk MGUS and 151 intermediate or high-risk MGUS; 66 had missing information precluding classification. Only three (<1% SMM cohort) were low-risk MGUS without abnormalities in hemoglobin, calcium, and renal function. In patients presenting with low-risk MGUS and normal hemoglobin, calcium, and renal function, the risk of missing a diagnosis of SMM and MM by omitting BM is <1%. BM should be deferred in these patients in preference to clinical and laboratory monitoring.

Utilizing multiparametric flow cytometry in the diagnosis of patients with primary plasma cell leukemia.

The diagnosis of primary plasma cell leukemia (pPCL) has been made by quantifying circulating plasma cells (cPCs) morphologically on a peripheral blood (PB) smear. However, this technique is not sufficiently sensitive. Multiparametric flow cytometry (MFC) provides a readily available and highly sensitive method to identify and quantify cPCs that could complement PB smear assessment. However, an optimal quantitative cutoff for cPCs by MFC to identify pPCL has not been established. Thus, a total of 591 patients newly diagnosed multiple myeloma (NDMM) patients who had their PB samples evaluated morphologically by PB smear, and immunophenotypically by MFC prior to beginning therapy were evaluated. The presence of ≥200 cPCs/µL by MFC (N = 25 or 5% of the total population) was chosen to identify patients with ≥5% cPCs by PB smear with a specificity of 99% and a sensitivity of 77%. For patients with ≥200 cPCs/µL by MFC compared to the remainder of the cohort, the median Time to next therapy (TTNT) was 18 vs 30 months and the median OS was 38 vs 70 months respectively. Thus, MFC assessment of PB can be utilized in conjunction with the morphological assessment of a PB smear to aid in improving the identification of pPCL among NDMM patients.

Blood mass spectrometry detects residual disease better than standard techniques in light-chain amyloidosis.

In patients with immunoglobulin light-chain (AL) amyloidosis, depth of hematologic response correlates with both organ response and overall survival. Our group has demonstrated that screening with a matrix-assisted laser desorption/ionization-time-of-flight (TOF) mass spectrometry (MS) is a quick, sensitive, and accurate means to diagnose and monitor the serum of patients with plasma cell disorders. Microflow liquid chromatography coupled with electrospray ionization and quadrupole TOF MS adds further sensitivity. We identified 33 patients with AL amyloidosis who achieved amyloid complete hematologic response, who also had negative bone marrow by six-color flow cytometry, and who had paired serum samples to test by MS. These samples were subjected to blood MS. Four patients (12%) were found to have residual disease by these techniques. The presence of residual disease by MS was associated with a poorer time to progression (at 50 months 75% versus 13%, p = 0.003). MS of the blood out-performed serum and urine immunofixation, the serum immunoglobulin free light chain, and six-color flow cytometry of the bone marrow in detecting residual disease. Additional studies that include urine MS and next-generation techniques to detect clonal plasma cells in the bone marrow will further elucidate the full potential of this technique.