A follow-up analysis of positron emission tomography/computed tomography in detecting hidden malignancies at the time of diagnosis of membranous nephropathy

Critical evaluation of cancer risks in glomerular disease

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The increased cancer incidence in patients with glomerular disease can be secondary to an intrinsic immune dysfunction associated with the disease or/and extrinsic factors, especially immunosuppressants.

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Paraneoplastic glomerulopathy is sometimes misdiagnosed as primary glomerulopathy.

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The treatment for paraneoplastic glomerulopathy is different from primary glomerular disease.

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In membranous nephropathy, serum circulating autoantibodies against PLA2R and THSD7A, immunohistochemical tissue markers for glomerular PLA2R, THSD7A and specific types of immunoglobulin G (IgG) may be used for identifying underlying malignancies.

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A scheme of screening of cancers frequently reported in the setting of glomerular disease is important.

The increased cancer incidence in patients with glomerular disease can be secondary to an intrinsic immune dysfunction associated with the disease or/and extrinsic factors, especially immunosuppressants. The treatment for paraneoplastic glomerulopathy is different from primary glomerular disease. Immunosuppressive therapy often used for primary glomerulopathy may aggravate concomitant cancers in patients with paraneoplastic glomerulopathy. In membranous nephropathy (MN), measurement of serum circulating autoantibodies against podocyte transmembrane glycoprotein M-type phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A), immunohistochemical staining of kidney tissue for glomerular PLA2R, THSD7A, neural epidermal growth factor-like 1 protein (NELL-1) and specific types of immunoglobulin G (IgG) may be useful adjuncts when screening for underlying malignancies. This review addresses overall cancer risks in individuals with glomerular diseases and employment of biomarkers available for MN. We propose a scheme of screening of cancers frequently reported in the setting of glomerular disease.

Paraneoplastic Glomerular Diseases

Paraneoplastic glomerular diseases (GNs) are rare manifestations in patients with underlying hematologic and solid organ malignancies and can occur before or after the detection of cancer. In the absence of established algorithms for investigation and reliable tests, they remain difficult to diagnose. Given the heterogeneity and infrequency of cases, the pathogenesis of most paraneoplastic GNs is poorly understood. Most of our recent understanding of paraneoplastic GNs has emerged from the discovery of target antigens in membranous nephropathy such as thrombospondin type-1 domain-containing protein 7A and neural epidermal growth factor-like 1 protein that appear to be promising in differentiating a primary vs paraneoplastic cause of membranous nephropathy. Treatment of paraneoplastic GNs is usually directed at the underlying malignancy. This review will focus on the epidemiology, pathogenesis, and diagnosis of paraneoplastic glomerular processes.

The evolution of the therapeutic approach to membranous nephropathy

Primary membranous nephropathy (MN) is a frequent cause of nephrotic syndrome (NS) in adults. In untreated patients, the outcome is variable, with one-third of the patients entering remission while the remaining ones show persisting proteinuria or progression to end-stage renal disease. Randomized clinical trials reported the efficacy of a 6-month regimen alternating intravenous and oral glucocorticoids with an alkylating agent every other month. The potential side effects of this regimen were limited by the fact that the use of glucocorticoids and alkylating agent did not exceed 3 months each. Two randomized trials with follow-ups (FU) up to 10 years provided assurance about the long-term efficacy and safety of this cyclical therapy. Calcineurin inhibitors have also been used successfully. However, in most responders, NS relapsed after the drug was withdrawn. Conflicting results have been reported with mycophenolate salts and adrenocorticotropic hormone. Observational studies reported good results with rituximab (RTX). Two controlled trials demonstrated the superiority of RTX over antiproteinuric therapy alone and cyclosporine. However, the FUs were relatively short and no randomized trial has been published against cyclical therapy. The available results, together with the discovery that most patients with MN have circulating antibodies against the phospholipase A2 receptor 1, support the use of cytotoxic drugs or RTX in MN. It is difficult to choose between these two different treatments. RTX is easier to use, but the FUs of the available studies are short, thus doubts remain about the long-term risk of relapses and the safety of repeated administrations of RTX.

Clinical significance of glomerular C3 deposition in primary membranous nephropathy

BACKGROUND

We aimed to investigate the effects of glomerular C3 deposition on clinical, histopathological features, and outcomes of patients with primary membranous nephropathy (MN).

METHODS

A total of 261 patients with biopsy-proven primary MN, who were on follow up for at least 6 months, were included in the study. The patients were grouped according to their C3 immunostaining in kidney biopsy samples at the time of diagnosis: Low intensity [LI; (C3 1 +)] and high intensity [HI; (C3 2 + or C3 3 +)]. The primary outcome was the development of kidney failure. Complete (CR) or partial remission (PR) was defined as secondary outcome.

RESULTS

Sixteen patients reached the primary outcome after a median follow-up of 33.8 months. Patients in the high intensity group (119 cases) had lower eGFR and higher proteinuria at admission and last follow-up compared to patients in the low intensity group (142 cases). Also, more patients in the high intensity group reached the primary outcome compared to patients in the low intensity group: twelve patients (10.1%) in the high intensity group and four patients (2.8%) in the low intensity group reached the primary outcome (p = 0.015). Kaplan-Meier analysis demonstrated that patients in the high intensity group had a higher risk for kidney failure (p = 0.02). In multivariate logistic regression analysis, high intensity C3 deposition and initial estimated glomerular filtration rate (eGFR) indepenently predicted primary outcome.

CONCLUSION

Extensive glomerular C3 deposition is a predictor of kidney failure in patients with MN.

Relationship between renal tissues phospholipase A2 receptor and its serum antibody and clinical condition and prognosis of idiopathic membranous nephropathy: a meta-analysis

Objective

To investigate the correlation of M-type phospholipase A2 receptor (PLA2R) expression and serum anti-PLA2R antibody with the clinical parameters and prognosis of patients with idiopathic membranous nephropathy (IMN).

Methods

A literature search for relevant original articles published between January 2009 and October 2019 was conducted on domestic and foreign databases. RevMan 5.3 software was used for meta-analysis.

Results

Eighteen studies were included in this meta-analysis. There were 1235 anti-PLA2R antibody-positive and PLA2R-positive patients, and 407 serum anti-PLA2R antibody-negative and PLA2R-negative patients. Compared with negative group, patients in the serum PLA2R antibody -positive group had lower serum albumin [SMD = -1.11, 95% CI (− 1.82, − 0.40), P < 0.00001], higher age [MD = 2.71, 95% CI (1.94, 3.48), P < 0.00001], and lower estimated glomerular filtration rate (eGFR) [MD = -10.34, 95% CI (− 12.09, − 8.60), P < 0.00001]; no significant between-group difference was observed with respect to 24-h urine protein and serum creatinine. However, no significant difference was observed between renal tissues PLA2R -positive and -negative groups with respect to serum albumin, eGFR, serum creatinine, and 24-h urine protein. Remission rate in the serum anti-PLA2R antibody -positive group was lower than that in the -negative group [OR = 0.41, 95% CI (0.28, 0.61),P < 0.00001]; however, no significant between-group difference in this respect was observed between the renal tissue PLA2R-positive and -negative groups. In the serum anti-PLA2R antibody -positive group, the higher titer subgroup had lower remission rate [OR = 0.19, 95% CI (0.07, 0.55),P = 0.002]. No significant difference was observed between anti-PLA2R antibody -positive and -negative groups with respect to adverse events. Serum anti-PLA2R antibody titer did not affect the adverse event rate.

Conclusion

As compared to PLA2R, serum anti-PLA2R antibody is more closely related with IMN disease progression.

Primary Membranous Glomerulonephritis: The Role of Serum and Urine Biomarkers in Patient Management

The detection of phospholipase A2 receptor (PLA2R) and thrombospondin domain containing 7A THSD7A among primary membranous glomerulonephritis (MGN) patients transformed the diagnosis, treatment monitoring, and prognosis. Anti-PLA2R can be detected in 70-90% of primary MGN patients while anti-THSD7A in 2-3% of anti-PLA2R negative primary MGN patients depending on the technique used. Serum and urine samples are less invasive and non-invasive, respectively, and thus can detect the presence of anti-PLA2R and anti-THSD7A with higher sensitivity and specificity, which is significant in patient monitoring and prognosis. It is better than exposing patients to a frequent biopsy, which is an invasive procedure. Different techniques of detection of PLA2R and THSD7A in patients' urine and sera were reviewed to provide newer and alternative techniques. We proposed the use of biomarkers (PLA2R and THSD7A) in the diagnosis, treatment decision, and follow-up of patients with primary MGN. In addition, other prognostic renal biomarkers like retinol binding protein (RBP) and beta-2 microglobulin were reviewed to detect the progression of renal damage for early intervention.

Biomarkers to detect membranous nephropathy in Chinese patients

Anti-M-type phospholipase A₂ receptor (anti-PLA₂R) is a widely accepted biomarker for clinical idiopathic membranous neurophathy (IMN). However, its ability to differentiate between IMN and secondary MN (SMN) is controversial. The objective of this study was to assess clinical MN biomarkers in blood, tissue and urine samples from Chinese patients. In total, 195 MN patients and 70 patients with other glomerular diseases were prospectively enrolled in the study. Participants were followed up for average of 17 months (range 3-39 months). Anti-PLA₂R and anti-THSD7A (thrombospondin type-1 domain-containing 7A) were detected only in MN patient sera and not in controls. Serum anti-THSD7A and THSD7A-positive biopsies were detected in 1/18 and 2/18 PLA₂R-negative MN cases, respectively. PLA₂R and THSD7A were detected in 72.27% and 40% of SMN cases, respectively. While serum positivity for both anti-PLA₂R and anti-THSD7A at the time of renal biopsy was specific to MN patients, neither antigen could discriminate between primary and secondary MN. We also found that high urinary levels of retinol binding protein (RBP) predicted poor proteinuria outcomes in study participants. Patients with low or medium urinary RBP levels achieved remission more frequently than those with high RBP.

Ultrasensitive Quantitation of Anti-Phospholipase A2 Receptor Antibody as A Diagnostic and Prognostic Indicator of Idiopathic Membranous Nephropathy

Anti-phospholipase A2 receptor antibody (PLA2R-Ab) is useful for affirming the diagnosis of idiopathic membranous nephropathy (IMN). Time-resolved fluoroimmunoassay (TRFIA) is highly sensitive and quantitative for measuring serum PLA2R-Ab immunoglobulin (IgG). We measured PLA2R-Ab levels with TRFIA in sera from 172 patients with IMN (n = 69), secondary MN (n = 9), and those with other glomerulonephritis (n = 94) at the time of renal biopsy compared to healthy controls (n = 286). Serum anti-PLA2R-IgG levels in healthy volunteers ranged from 0.09–0.91 mg/L. We set the cutoff value of the anti-PLA2R-IgG titer at 0.91 mg/L, with a sensitivity of 84.06% for diagnosing IMN. Increasing the cut-off value to 2.025 mg/L altered the sensitivity for diagnosing IMN to 71.01%, but with 100% specificity. IMN patients had significantly higher serum anti-PLA2R-IgG levels compared to those with secondary MN. PLA2R-Ab titers negatively correlated with estimated glomerular filtration rate (eGFR). Patinets with high titers had significantly lower serum albumin and eGFR, higher proteinuria and serum creatinine levels, accompanied by a lower complete remission rate. High titers of PLA2R-Ab were associated with poor prognosis of patients with IMN. TRFIA-based quantification of anti-PLA2R-IgG can be a reliable approach for the diagnosis and prognostication of patients with IMN.