Extramedullary involvement (or extramedullary disease, EMD) represents an aggressive form of multiple myeloma (MM), characterized by the ability of a clone and/or subclone to thrive and grow independent of the bone marrow microenvironment. Several different definitions of EMD have been used in the published literature. We advocate that true EMD is restricted to soft-tissue plasmacytomas that arise due to hematogenous spread and have no contact with bony structures. Typical sites of EMD vary according to the phase of MM. At diagnosis, EMD is typically found in skin and soft tissues; at relapse, typical sites involved include liver, kidneys, lymph nodes, central nervous system (CNS), breast, pleura, and pericardium. The reported incidence of EMD varies considerably, and differences in diagnostic approach between studies are likely to contribute to this variability. In patients with newly diagnosed MM, the reported incidence ranges from 0.5% to 4.8%, while in relapsed/refractory MM the reported incidence is 3.4 to 14%. Available data demonstrate that the prognosis is poor, and considerably worse than for MM without soft-tissue plasmacytomas. Among patients with plasmacytomas, those with EMD have poorer outcomes than those with paraskeletal involvement. CNS involvement is rare, but prognosis is even more dismal than for EMD in other locations, particularly if there is leptomeningeal involvement. Available data on treatment outcomes for EMD are derived almost entirely from retrospective studies. Some agents and combinations have shown a degree of efficacy but, as would be expected, this is less than in MM patients with no extramedullary involvement. The paucity of prospective studies makes it difficult to justify strong recommendations for any treatment approach. Prospective data from patients with clearly defined EMD are important for the optimal evaluation of treatment outcomes.

The multicenter retrospective study conducted in 38 centers from 20 countries including 172 adult patients with CNS MM aimed to describe the clinical and pathological characteristics and outcomes of patients with multiple myeloma (MM) involving the central nervous system (CNS). Univariate and multivariate analyses were performed to identify prognostic factors for survival. The median time from MM diagnosis to CNS MM diagnosis was 3 years. Thirty‐eight patients (22%) were diagnosed with CNS involvement at the time of initial MM diagnosis and 134 (78%) at relapse/progression. Upon diagnosis of CNS MM, 97% patients received initial therapy for CNS disease, of which 76% received systemic therapy, 36% radiotherapy and 32% intrathecal therapy. After a median follow‐up of 3.5 years, the median overall survival (OS) from the onset of CNS involvement for the entire group was 7 months. Untreated and treated patients had median OS of 2 and 8 months, respectively (P < 0.001). At least one previous line of therapy for MM before the diagnosis of CNS disease and >1 cytogenetic abnormality detected by FISH were independently associated with worse OS. The median OS for patients with 0, 1 and 2 of these risk factors were 25 months, 5.5 months and 2 months, respectively (P < 0.001). Neurological manifestations, not considered chemotherapy‐related, observed at any time after initial diagnosis of MM should raise a suspicion of CNS involvement. Although prognosis is generally poor, the survival of previously untreated patients and patients with favorable cytogenetic profile might be prolonged due to systemic treatment and/or radiotherapy. Am. J. Hematol. 91:575–580, 2016.

The phase 3 CLARION study compared carfilzomib-melphalan-prednisone (KMP) with bortezomib-melphalan-prednisone (VMP) in transplant-ineligible newly diagnosed multiple myeloma (NDMM) patients. Patients were randomized 1:1 to KMP or VMP for nine 42-day cycles (C). Patients received carfilzomib on days (D) 1, 2, 8, 9, 22, 23, 29, 30 (20 mg/m2: C1D1, C1D2; 36 mg/m2 thereafter) or bortezomib on D1, 4, 8, 11, 22, 25, 29, 32 (1.3 mg/m2; D4, 11, 25, 32 omitted for C5-9). Melphalan (9 mg/m2) and prednisone (60 mg/m2) were administered on D1-4. The primary endpoint was progression-free survival (PFS). Nine hundred fifty-five patients were randomized (intention-to-treat population: KMP, n = 478; VMP, n = 477). Median PFS was 22.3 months with KMP vs 22.1 months with VMP (hazard ratio [HR], 0.906; 95% confidence interval [CI], 0.746-1.101; P = .159). Median overall survival was similar and not reached in either group (HR, 1.08; 95% CI, 0.82-1.43). Overall response rate was 84.3% for KMP and 78.8% for VMP. Complete response rate was 25.9% for KMP and 23.1% for VMP. Minimal residual disease–negative rates were 15.7% (KMP) and 15.5% (VMP). Adverse events (AEs) of interest (any grade) occurring with a ≥5% higher patient incidence in the KMP arm were acute renal failure (13.9% [KMP] vs 6.2% [VMP]) and cardiac failure (10.8% vs 4.3%). Grade ≥3 AE rates were 74.7% (KMP) and 76.2% (VMP). Grade ≥2 peripheral neuropathy was lower for KMP vs VMP (2.5% vs 35.1%). Treatment with KMP in CLARION did not yield a statistically significant difference in PFS vs VMP. This trial was registered at www.clinicaltrials.gov as #NCT01818752.

Monoclonal gammopathy of renal significance (MGRS) is a recognized clinical entity. Literature regarding treatment and its outcomes in MGRS is sparse due to the rarity and misdiagnosis of MGRS. We retrospectively analyzed 280 adults with an MGRS diagnosis from 2003 to 2020 across 19 clinical centers from 12 countries. All cases required renal biopsy for the pathological diagnosis of MGRS. Amyloidosis‐related to MGRS (MGRS‐A) was present in 180 patients; nonamyloidosis MGRS (MGRS‐NA), including a broad spectrum of renal pathologies, was diagnosed in 100 patients. The median overall survival in the studied cohort was 121.0 months (95% CI: 105.0–121.0). Patients with MGRS‐A had a shorter overall survival than patients with MGRS‐NA (HR = 0.41, 95%CI: 0.25–0.69; p = 0.0007). Both hematologic and renal responses were associated with longer survival. Achievement of ≥VGPR was generally predictive of a renal response (OR = 8.03 95%CI: 4.04–115.96; p < 0.0001), one‐fourth of patients with ≥VGPR were renal nonresponders. In MGRS‐A, factors associated with poor prognosis included elevated levels of creatinine, beta‐2‐microglobulin, and hemodialysis at diagnosis. In MGRS‐NA, only age >65 years was associated with increased risk of death. Treatments provided similar hematologic response rates in both types of MGRS. Autologous stem cell transplantation led to better response than other treatments. This multicenter and international effort is currently the largest report on MGRS.