Kidney outcomes and prognostic factors of myeloma associated acute kidney injury in the contemporary era

Myeloma cast nephropathy (MCN) has historically been associated with poor kidney outcomes. We aimed to evaluate the kidney outcomes and identify prognostic factors of myeloma-associated acute kidney injury (M-AKI) in the contemporary era of anti-plasma cell therapy. Patients who received anti-myeloma therapy with M-AKI (January 2012 to June 2020) from a single centre were identified from electronic medical records. Diagnosis of MCN was either biopsy confirmed (BC) or clinically suspected (CS), the latter defined as acute kidney injury with reduced estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m2 and involved serum free light chains (iSFLC) >500 mg/L at diagnosis. Twenty-six patients with M-AKI were identified (BC: n = 13, CS: n = 13). Median eGFR at diagnosis was 12 (interquartile range 6-20) mL/min/1.73 m2 . All six dialysis-requiring patients achieved dialysis independence after 71 (43-208) days. The best-achieved eGFR was 47 (32-67) mL/min/1.73 m2 after 120 (63-167) days post-treatment, which was maintained at 47 (33-66) mL/min/1.73 m2 12 months post-treatment. Patients with best-achieved eGFR above the median were more likely to have achieved an iSFLC of <20 mg/L (above median group 62% versus below median group 0%; p < .001) and lower best post-treatment iSFLC (20 (12-90) versus 67 (29-146) mg/L; p < .05). Best-achieved iSFLC was a prognostic factor for superior eGFR following treatment for M-AKI. Despite low eGFR at diagnosis, contemporary anti-myeloma therapy can achieve significant recovery of kidney function.

Myeloma Cast Nephropathy an Unusual Association with HIV Infection Presenting with Renal Dysfunction

Human immunodeficiency virus (HIV)-associated renal disease is a pan-nephropathy, causing glomerular, tubular, and interstitial changes. The common lesion is the collapsing variant of focal segmental glomerulosclerosis. Multiple myeloma presenting as light chain cast nephropathy in an HIV-positive patient is very rare. A 45-year-old female retropositive patient presented with one episode of hematuria. Kidney biopsy was performed with a clinical diagnosis of acute interstitial nephritis (AIN). Biopsy showed unremarkable glomeruli. Tubules were dilated and showed a few periodic acid-Schiff (PAS) positive and many PAS-negative fractured casts surrounded by histiocytic reaction. Immunofluorescence and immunohistochemistry (IHC) showed lambda restriction by the casts. Bone marrow aspirate showed an increase in plasma cells, and the biopsy showed nodular aggregates of atypical plasma cells, which showed lambda restriction by IHC. PAS-negative fractured tubular casts are known to be associated with HIV-related nephropathy and need detailed hematological workup to rule out an associated plasma cell dyscrasia.

Crystals, crystals everywhere but not a clue till late… Light chain crystalline proximal tubulopathy with concomitant myeloma cast nephropathy

The renal diseases commonly associated with myeloma include primary amyloidosis, cast nephropathy, and light chain deposition disease. Less frequent forms of renal involvement encountered in the course of myeloma are crystalline and non-crystalline proximal tubulopathies, neoplastic plasma cell infiltration, and immunoglobulin crystallization in interstitial histiocytes and glomerular cells including podocytes. Light chain proximal tubulopathy (LCPT) caused by aggregation of non-crystalline and rarely crystalline deposits of monoclonal light chains in the cytoplasm of proximal tubular epithelial cells, accounts for less than 5% of monoclonal gammopathy-associated kidney diseases. We report the case of a 48-year-old Indian woman with multiple myeloma, who presented with acute kidney injury and nephrotic syndrome, in whom the renal biopsy revealed widespread crystalline inclusions in extraglomerular and glomerular compartments. We present illustrative light microscopic (LM) and diagnostic electron microscopic (EM) findings of this case which enabled a diagnosis of crystalline LCPT, crystal storing histiocytosis, and crystalline podocytopathy occurring synchronously with myeloma cast nephropathy. While documenting this unique juxtapositioning of multicompartmental paraproteinemic renal injury in multiple myeloma, diagnosed after EM analysis of the patient's renal biopsy, we discuss the pathogenetic pathways of this condition along with the clinical implications. Due to intrinsic structural properties of the crystals, they frequently escape detection by routine LM, necessitating EM analysis for their diagnosis. Given the prognostic implications of tubulopathies complicating myeloma, LCPT is a critically important diagnosis, highlighting the need for a comprehensive renal biopsy evaluation inclusive of EM for the practice of precision medicine in such scenarios.

Monoclonal Immunoglobulin-Associated Renal Lesions in Patients with Newly Diagnosed Multiple Myeloma: A Report from a Single Center

Background

Monoclonal immunoglobulin-associated renal lesions in patients with newly diagnosed myeloma vary. We aimed to determine the pathological spectrum and analyze associated prognostic factors.

Methods

Fifty-six patients with newly diagnosed multiple myeloma and biopsy-proven renal lesions were enrolled. Kidney biopsies were reanalyzed, and the baseline clinical characteristics, treatments and outcomes were recorded.

Results

Fifty-one patients had monoclonal immunoglobulin-associated renal lesions, with myeloma cast nephropathy (MCN) being the most common pattern. We divided our cohort into pure MCN, MCN+ other pathologies and non-MCN. Patients with MCN had more severe renal injury than those with non-MCN. In our cohort, none of the patients with pure MCN or MCN + other pathologies presented with nephrotic syndrome. Patients with non-MCN had better renal and overall survival than those with pure MCN but similar survivals to those with MCN + other pathologies. Number of myeloma casts (HR 1.08, p = 0.012) was the only independent prognostic factor for renal survival. Male sex (HR: 3.64; p = 0.015) and number of casts (HR: 1.17; p = 0.001) were independent prognostic factors for overall survival.

Conclusion

Patients with MCN had more severe renal injury than those with non-MCN. Patients with non-MCN had better renal and overall outcomes than those with pure MCN, but their outcomes were similar to those with MCN + other pathologies. The independent predictors of overall survival were male sex and number of myeloma casts.

Effect of high cut-off dialysis for acute kidney injury secondary to cast nephropathy in patients with multiple myeloma: a systematic review and meta-analysis

Background

Acute kidney injury (AKI) caused by cast nephropathy is associated with increased morbidity and mortality among patients with multiple myeloma (MM). High cut-off haemodialysis (HCO-HD) has proven to be effective in the removal of serum light chains but the effect on clinical outcomes, especially renal recovery, remains uncertain.

Methods

A systematic review and meta-analysis were performed examining all randomized controlled trials (RCTs) and observational studies (OBSs) assessing the effect of HCO-HD on clinical outcomes of patients with MM complicated by cast nephropathy–induced severe AKI. The primary outcome was all-cause mortality at the end of the study. The secondary outcomes included all-cause mortality at 12 months, HD independence and serum kappa and lambda light chain reduction. Pooled analysis was performed using random effects models.

Results

We identified five studies, comprising two RCTs and three retrospective cohort studies, including 276 patients with a mean follow-up of 18.7 months. The majority of the studies were of suboptimal quality and underpowered. Compared with patients treated with conventional HD, HCO-HD was not associated with a survival benefit at 12 months {five studies, 276 patients, relative risk [RR] 1.02 [95% confidence interval (CI) 0.76–1.35], I² = 33.9%} or at the end of the studies at an average of 34 months [five studies, 276 patients, RR 1.32 (95% CI 0.71–2.45), I² = 62.0%]. There was no difference in HD independence at 90 days [two trials, 78 patients, RR 2.23 (95% CI 1.09–4.55)], 6 months [two studies, 188 patients, RR 1.19 (95% CI 0.68–2.06)] or 12 months [two studies, 188 patients, RR 1.14 (95% CI 0.58–2.26)]. Patients receiving HCO dialysis, however, had a greater reduction in serum kappa [two studies, 188 patients, weighted mean difference (WMD) 46.7 (95% CI 38.6–54.7), I² =  52.0%] and lambda [two studies, 188 patients, WMD 50.3 (95% CI 21.4–79.3), I² = 95.1%] light chain levels.

Conclusion

Current evidence from RCTs and OBSs suggests HCO dialysis is able to reduce serum free light chains but makes no significant improvement in all-cause mortality and renal outcomes compared with conventional HD for patients with myeloma cast nephropathy. However, there is a trend towards better renal outcomes with the use of HCO dialysis. The lack of long-term data and the small sample sizes of the included studies limit this analysis. Therefore further large-scale RCTs with longer follow-up are needed to assess the effect of HCO dialysis on clinical outcomes in patients with myeloma cast nephropathy.

Perspectives From an Onconephrology Interest Group: Conference Report

Introduction and objective:

Onconephrology is a new and evolving field that deals with kidney complications in patients with cancer as well as the management of cancer in patients with preexisting kidney disease. With increasing numbers of patients with cancer with kidney-related complications, the field has garnered increased attention. Thus, an annual Greater Toronto Area Onconephrology Interest Group symposium was held in May 2019. The objective of the meeting was to demonstrate the junctures between oncology and nephrology by highlighting recent data regarding (1) kidney impairment in solid organ malignancies, (2) management and treatment of kidney cancer, (3) kidney impairment in hematologic malignancies, (4) malignancy and kidney transplantation, and (5) hyponatremia in patients with cancer.

Methods and sources of information:

Through a structured presentation, the group explored key topics discussed at a Kidney Disease Improving Global Outcomes (KDIGO) Controversies Conference on Onconephrology. Expert opinions, clinical trial findings, and publication summaries were used to illustrate patient and treatment-related considerations in onconephrology.

Key findings:

Kidney complications in patients with cancer are a central theme in onconephrology. An estimated 12% to 25% of patients with solid organ malignancies have chronic kidney disease (CKD), although in certain cancers, the prevalence of CKD is higher. Kidney impairment is also a common complication of some hematologic malignancies. The incidence of renal failure in patients with multiple myeloma is estimated at 18% to 56% and light chain cast nephropathy is seen in approximately 30% of these patients. In addition, there appears to be a bidirectional relationship between kidney cancer and CKD, with some data sets suggesting the risk increases as kidney function declines. Cancer is also of concern in patients with preexisting kidney disease. Kidney transplant recipients have a greater risk of cancer and a higher risk of cancer-related mortality. Kidney complications have also been associated with novel cancer therapies, such as immune checkpoint inhibitors and chimeric antigen receptor (CAR) T-cell therapy. An estimated 2% to 4% of patients initiating an immune checkpoint inhibitor may develop nephrotoxicity, whereas up to 40% of patients on CAR T-cell therapy experience cytokine release syndrome (CRS). Tumor lysis syndrome and electrolyte abnormalities, such as hyponatremia, have also been reported with CAR T-cell therapy. While the incidence and prevalence of hyponatremia vary depending on the cancer type and serum sodium cutoff point, hyponatremia may be seen in up to 46% of patients hospitalized in cancer centers.

Conclusions:

Onconephrology is a developing field and the themes arising from this meeting indicate a need for greater collaboration between oncologists and nephrologists. Educational symposia and onconephrology fellowship programs may allow for improved cancer care for patients with kidney disease.

[Morphological and immunohistochemical predictors of renal response to therapy patients with myeloma cast nephropathy and dialysis-dependent acute kidney injury]

AIM

Reveal morphological and immunohistochemical predictors of reversibility of dialysis-dependent acute kidney injury (AKI) in patients with myeloma cast nephropathy (MCN) based on the study of kidney biopsy.

MATERIALS AND METHODS

Renal pathological findings were studied in 36 patients with MCN and dialysis-dependent stage 3 AKI (AKIN, 2012). The study of biopsy samples was performed by a semi-quantitative and quantitative analysis using computer morphometry. The expression of E-cadherin, vimentin and-smooth muscle actin was determined immunohistochemically in the tubular cells and interstitium. Induction therapy for 26 patients was carried out to bortezomib-based programs; in 10 patients other schemes were used. A comparative analysis of morphological changes in nephrobiopathy depending on the renal response was performed in patients with achieved hematologic remission.

RESULTS

Improved renal function was observed only in patients with hematologic response to therapy. There were no differences in the number of sclerotic glomeruli, protein casts, the area of inflammatory interstitial infiltration, and the degree of acute tubular damage in patients with and without renal response. In patients with renal response compared with patients without improving renal function, the area of interstitial fibrosis was less (24.9% and 45.9%, respectively;p=0.001), and the area of E-cadherin expression was larger (15.9% and 7.1%, respectively;p=0.006). Interstitial fibrosis of 40% or more and/or the area of expression of E-cadherin less than 10% of the area of tubulo-interstitium have an unfavorable prognostic value in achieving a renal response in MCN.

CONCLUSION

If the interstitial fibrosis area is 40% or more and the expression area of E-cadherin is less than 10%, the probability of the absence of a renal response is 93.3% (OR=24.5) even when a hematological response to induction therapy is achieved. The number of protein casts, the prevalence of acute tubular damage and inflammatory interstitial infiltration have not prognostic value.

Treatment of multiple myeloma with renal involvement: the nephrologist's view

Renal injury is a common complication in multiple myeloma (MM). In fact, as many as 10% of patients with MM develop dialysis-dependent acute kidney injury related to increased free light chain (FLC) production by a plasma cell clone. Myeloma cast nephropathy (MCN) is the most prevalent pathologic diagnosis associated with renal injury, followed by light chain deposition disease and light chain amyloidosis. Several FLC removal techniques have been explored to improve kidney disease in MM but their impact on renal clinical outcomes remains unclear. According to the evidence, high cut-off haemodialysis should be restricted to MM patients on chemotherapy with histological diagnosis of MCN and haemodialysis requirements. From our perspective, more efforts are needed to improve kidney outcomes in patients with MM and renal failure.

Managing renal complications in multiple myeloma

INTRODUCTION

About 20-40% of patients with multiple myeloma (MM) will present with some degree of renal impairment (RI) and about 25% of patients will experience RI at later disease stages. Patients with MM and RI have poorer overall survival and are at higher risk of early death.

AREAS COVERED

The mechanisms of acute renal damage in MM are covered and the issues around diagnosis and renal evaluation response are discussed. The importance of optimal supportive care is stressed and the role and effectiveness of different anti-myeloma agents covered including the role of high cut-off hemodialysis, autologous stem cell transplantation and kidney transplant. Expert commentary: Outcomes of patients with RI and rates of renal recovery have improved with the use of novel anti-myeloma agents. Bortezomib-dexamethasone backbone regimes (±third agent) are the current first choice in newly diagnosed patients. In relapsed/refractory disease additional treatment options include newer novel agents.

Prognostic value of kidney biopsy in myeloma cast nephropathy: a retrospective study of 70 patients

BACKGROUND

Light chain myeloma cast nephropathy (MCN) is the major cause of renal failure in multiple myeloma and strongly impacts patient survival. The role of kidney biopsy in the management of MCN is unclear.

METHODS

Renal pathological findings were retrospectively studied in 70 patients with multiple myeloma and MCN. Patients were categorized according to the achievement or not of renal response, as defined by estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m(2) and/or dialysis independence at 3 months.

RESULTS

Thirty-two patients (46%) achieved a renal response. In the whole study population, the following parameters differed significantly between patients with and without renal response, respectively: baseline median eGFR (13.3 versus 9.3 mL/min/1.73 m(2), P = 0.017), Acute Kidney Injury Network Stage 3 (68.8 versus 92.1%, P = 0.019), haematological response rate (94 versus 34%, P < 0.0001), median percentage of free light chain (FLC) reduction at Day 21 (92 versus 24%, P = 0.006) and median number of casts/10 fields (14 versus 25, P = 0.005). The extent of interstitial fibrosis and tubular atrophy was similar. In multivariate analysis, only FLC reduction at Day 21 was significantly associated with renal response. However, when considering only the subgroup of haematological responders, both median number of casts [odds ratio (OR) = 0.93, 95% confidence interval (95% CI): 0.88-0.98, P = 0.01] and extent of tubular atrophy (OR = 0.03, 95% CI: 0.00-0.52, P = 0.02) were independent predictors of renal response.

CONCLUSIONS

In MCN, the presence of numerous casts and diffuse tubular atrophy is associated with poor renal prognosis. These data suggest that additional strategies to reduce FLC burden should be considered in patients with extensive cast formation.

Hypophosphatemic osteomalacia: an unusual clinical presentation of multiple myeloma

An unusual case of a 75-year-old man is presented who had multiple stress fractures due to adult onset hypophosphatemic osteomalacia, which was the result of Fanconi syndrome, with light chain cast proximal tubulopathy due to multiple myeloma. A 75-year-old man presented with diffuse pain and muscle weakness. He had multiple stress fractures, low serum phosphate, decreased renal tubular reabsorption of phosphate, and normal PTH and FGF23, indicating adult onset hypophosphatemic osteomalacia. Phosphate supplements with calcitriol resulted in clinical recovery and healing of stress fractures. Because of proteinuria, a renal biopsy was performed that revealed Fanconi syndrome with light chain cast proximal tubulopathy and light kappa chains were found in serum and urine. A bone biopsy confirmed the diagnosis of multiple myeloma, and treatment with chemotherapy resulted in cytological and clinical recovery.

Clinical and prognostic differences among patients with light chain deposition disease, myeloma cast nephropathy and both

In some patients with light chain deposition disease (LCDD) there is also evidence of myeloma cast nephropathy (MCN) on renal biopsy. The purpose of this study was to evaluate the renal and survival outcome of patients with concomitant diagnosis of MCN and LCDD to LCDD and MCN alone. Eighty seven patients were identified and divided into LCDD (n=45), MCN (n=29), and LCDD+ MCN (n=13). Patients with LCDD+ MCN had a worse overall survival (OS) compared to patients with LCDD (p=0.03), but similar to patients with MCN (p=0.4). Death-censored renal survival was no different amongst the groups. Presenting with acute renal failure at time of renal biopsy (HR 7.2, p=0.0002) was an independent poor renal prognostic factor while older age (HR 1.06, p=0.0002), presence of osteolytic lesions (HR 4.4, p<0.0001), and requirement for dialysis or creatinine≥5 mg/dL (HR 3.2, p=0.0006) at time of renal biopsy were independent poor prognostic factors for OS.

Molecular mechanisms of crystal-related kidney inflammation and injury. Implications for cholesterol embolism, crystalline nephropathies and kidney stone disease

Crystals are particles of endogenous inorganic or organic composition that can trigger kidney injury when deposited or formed inside the kidney. While decades of research have focused on the molecular mechanisms of solute supersaturation and crystal formation, the pathomechanisms of crystal-induced renal inflammation remain largely unknown. The recent discovery of the intracellular NLRP3 inflammasome as a pattern recognition platform that translates crystal uptake into innate immune activation via secretion of IL-1β and IL-18 revised the pathogenesis of gout, silicosis, asbestosis, atherosclerosis and other crystal-related disorders. As a proof of concept, the NLRP3 inflammasome was now shown to trigger inflammation and acute kidney injury (AKI) in oxalate nephropathy. It seems likely that this and potentially other innate immunity mechanisms drive crystalline nephropathies (CNs) that are associated with crystals of calcium phosphate, uric acid, cysteine, adenine, certain drugs or contrast media, and potentially of myoglobin during rhabdomyolysis and of light chains in myeloma. Here, we discuss the proven and potential mechanisms of renal inflammation and kidney injury in crystal-related kidney disorders. In addition, we list topics for further research in that field. This perspective may also provide novel therapeutic options that can help to avoid progressive tissue remodeling and chronic kidney disease in patients with kidney stone disease or other CNs.