Onconephrology: Core Curriculum 2023.

Onconephrology focuses on management of kidney disease in cancer, which manifests itself in a variety of clinical syndromes, including acute kidney injury, chronic kidney disease, hypertension, proteinuria, and electrolyte disorders. Many of these syndromes result from cancer treatments including chemotherapy, immunotherapy, chimeric antigen receptor T cells, and stem cell transplant. Others are due to kidney-specific effects of the cancer, as seen with monoclonal gammopathy or glomerular diseases associated with malignancy. Further, cancer risk itself is heightened in patients with kidney disease, particularly kidney transplant recipients, and their care requires specific considerations. In this installment of AJKD's Core Curriculum in Nephrology, we review these and other core concepts in onconephrology, using a case-based approach to highlight clinical decision making.

Onco-Nephrology: Kidney Disease in the Cancer Patient.

Patients with cancer may develop kidney disease with a variety of different clinical manifestations including acute kidney injury, chronic kidney disease, hypertension, proteinuria and electrolyte disturbances. Onco-nephrology is the subspecialty of nephrology that diagnoses and manages kidney disease in patients with cancer. In this article, we review major topics in Onco-Nephrology that may be encountered by the general internist.

Chemotherapy-Associated Thrombotic Microangiopathy.

Thrombotic microangiopathy (TMA) is a syndrome of microangiopathic hemolytic anemia and thrombocytopenia with end-organ dysfunction. Although the advent of plasma exchange, immunosuppression, and complement inhibition has improved morbidity and mortality for primary TMAs, the management of secondary TMAs, particularly drug-induced TMA, remains less clear. TMA related to cancer drugs disrupts the antineoplastic treatment course, increasing the risk of cancer progression. Chemotherapeutic agents such as mitomycin-C, gemcitabine, and platinum-based drugs as well as targeted therapies such as antiangiogenesis agents and proteasome inhibitors have been implicated in oncotherapy-associated TMA. Among TMA subtypes, drug-induced TMA is less well-understood. Treatment generally involves withdrawal of the offending agent and supportive care targeting blood pressure and proteinuria reduction. Immunosuppression and therapeutic plasma exchange have not shown clear benefit. The terminal complement inhibitor, eculizumab, has shown promising results in some cases of chemotherapy-associated TMA including in re-exposure. However, the data are limited, and unlike in primary atypical hemolytic uremic syndrome, the role of complement in the pathogenesis of drug-induced TMA is unclear. Larger multicenter studies and unified definitions are needed to elucidate the extent of the problem and potential treatment strategies.

Cancer Drug Dosing in Chronic Kidney Disease and Dialysis.

Patients with malignancies have a high prevalence of kidney disease and are often treated with antineoplastic agents that undergo kidney metabolism or excretion or clearance via renal replacement therapies. Thus, the dosing of these agents, including classic chemotherapeutic drugs, targeted therapies, and immunotherapy, must take into account patients' kidney function. In this review, we will discuss the pitfalls of accurate measurement of kidney function and how kidney disease affects both pharmacodynamic and pharmacokinetic properties of drugs. Lastly, we will discuss specific agents and summarize current dosing strategies for use in patients with chronic kidney disease and end-stage kidney disease.

Mortality after acute kidney injury and acute interstitial nephritis in patients prescribed immune checkpoint inhibitor therapy.

BACKGROUND: In patients receiving immune checkpoint inhibitor (ICI) therapy, acute kidney injury (AKI) is common, and can occur either from kidney injury unrelated to ICI use or from immune activation resulting in acute interstitial nephritis (AIN). In this study, we test the hypothesis that occurrence of AIN indicates a favorable treatment response to ICI therapy and therefore among patients who develop AKI while on ICI therapy, those with AIN will demonstrate greater survival compared with others with AKI. METHODS: In this observational cohort study, we included participants initiated on ICI therapy between 2013 and 2019. We tested the independent association of AKI and estimated AIN (eAIN) with mortality up to 1 year after therapy initiation as compared with those without AKI using time-varying Cox proportional hazard models controlling for demographics, comorbidities, cancer type, stage, and therapy, and baseline laboratory values. We defined eAIN as those with a predicted probability of AIN >90th percentile derived from a recently validated diagnostic model. RESULTS: Of 2207 patients initiated on ICIs, 617 (28%) died at 1 year and 549 (25%) developed AKI. AKI was independently associated with higher mortality (adjusted HR, 2.28 (95% CI 1.90 to 2.72)). Those AKI patients with eAIN had more severe AKI as reflected by a higher peak serum creatinine (3.3 (IQR 2.1-6.1) vs 1.4 (1.2-1.9) mg/dL, p<0.001) but exhibited lower mortality than those without eAIN in univariable analysis (HR 0.43 (95% CI 0.21 to 0.89)) and after adjusting for demographics, comorbidities, and cancer type and severity (adjusted HR 0.44 (95% CI 0.21 to 0.93)). CONCLUSION: In patients treated with ICI, mortality was higher in those with AKI unrelated to ICI but lower in those where the underlying etiology was AIN. Future studies could evaluate the association of biopsy-proven or biomarker-proven AIN with mortality in those receiving ICI therapy.

Miglustat Therapy for SCARB2-Associated Action Myoclonus-Renal Failure Syndrome.

OBJECTIVE: We evaluated whether substrate reduction therapy with miglustat could alter the course of action myoclonus-renal failure syndrome (AMRF), a rare, progressive myoclonic epilepsy with early mortality caused by scavenger receptor class B member 2 (SCARB2) gene mutations. METHODS: We identified an AMRF patient with a biallelic combination of SCARB2 mutations determined by whole exome sequencing. SCARB2 encodes a protein that traffics ß-glucocerebrosidase to the lysosomal membrane. Mutations lead to a complex pattern of glucosylceramide accumulation and neurologic symptoms including progressive action myoclonus, seizures, and ataxia. We then evaluated the effect of inhibiting glucosylceramide synthesis, as is used in Gaucher disease. The patient was treated for 3 years with miglustat after several years of steady worsening. RESULTS: Progression of myoclonus halted, dysphagia resolved, some skills were reacquired, and seizures remained well controlled. CONCLUSIONS: The response suggests that neurologic symptoms of SCARB2-associated AMRF could be ameliorated, at least partly, by targeting glycosphingolipid metabolism with available medications.

Clinical Features and Outcomes of Immune Checkpoint Inhibitor-Associated AKI: A Multicenter Study.

BACKGROUND: Despite increasing recognition of the importance of immune checkpoint inhibitor-associated AKI, data on this complication of immunotherapy are sparse. METHODS: We conducted a multicenter study of 138 patients with immune checkpoint inhibitor-associated AKI, defined as a ≥2-fold increase in serum creatinine or new dialysis requirement directly attributed to an immune checkpoint inhibitor. We also collected data on 276 control patients who received these drugs but did not develop AKI. RESULTS: Lower baseline eGFR, proton pump inhibitor use, and combination immune checkpoint inhibitor therapy were each independently associated with an increased risk of immune checkpoint inhibitor-associated AKI. Median (interquartile range) time from immune checkpoint inhibitor initiation to AKI was 14 (6-37) weeks. Most patients had subnephrotic proteinuria, and approximately half had pyuria. Extrarenal immune-related adverse events occurred in 43% of patients; 69% were concurrently receiving a potential tubulointerstitial nephritis-causing medication. Tubulointerstitial nephritis was the dominant lesion in 93% of the 60 patients biopsied. Most patients (86%) were treated with steroids. Complete, partial, or no kidney recovery occurred in 40%, 45%, and 15% of patients, respectively. Concomitant extrarenal immune-related adverse events were associated with worse renal prognosis, whereas concomitant tubulointerstitial nephritis-causing medications and treatment with steroids were each associated with improved renal prognosis. Failure to achieve kidney recovery after immune checkpoint inhibitor-associated AKI was independently associated with higher mortality. Immune checkpoint inhibitor rechallenge occurred in 22% of patients, of whom 23% developed recurrent associated AKI. CONCLUSIONS: This multicenter study identifies insights into the risk factors, clinical features, histopathologic findings, and renal and overall outcomes in patients with immune checkpoint inhibitor-associated AKI.

Immune checkpoint inhibitor nephrotoxicity: what do we know and what should we do?

Immune checkpoint inhibitors have dramatically improved cancer therapy for many patients. These humanized monoclonal antibodies against various immune checkpoints (receptors and ligands) effectively treat a number of malignancies by unleashing the immune system to destroy cancer cells. These drugs are not excreted by the kidneys or liver, have a long half-life, and undergo receptor-mediated clearance. Although these agents have greatly improved the prognosis of many cancers, immune-related end organ injury is a complication that has come to light in clinical practice. Although less common than other organ involvement, kidney lesions resulting in acute kidney injury and/or proteinuria are being described. Acute tubulointerstitial nephritis is the most common lesion seen on kidney biopsy, while acute tubular injury and glomerular lesions occur less commonly. Clinical findings and laboratory tests are suboptimal in predicting the underlying renal lesion, making kidney biopsy necessary in the majority of cases to definitely diagnose the lesion and potentially guide therapy. Immune checkpoint inhibitor discontinuation and corticosteroid therapy are recommended for acute tubulointerstitial nephritis. Based on a handful of cases, re-exposure to these drugs in patients who previously developed acute tubulointerstitial nephritis has been mixed. Although it is unclear whether re-exposure is appropriate, it should perhaps be considered in patients with limited options. When this approach is taken, patients should be closely monitored for recurrence of acute kidney injury. Treatment of cancer in patients with a kidney transplant with immune checkpoint inhibitors risks the development of acute rejection in some patients and requires close surveillance.

Cardiorenal complications of immune checkpoint inhibitors.

The development of immune checkpoint inhibitors (ICIs) has driven a revolutionary change in cancer treatment. Although traditional chemotherapeutic agents remain the first-line option for most cancers, targeted immune therapies are emerging as standard treatments for advanced-stage cancers. These agents target cell surface checkpoint proteins to stimulate the recognition and destruction of cancer cells by the immune system. Clinical studies have demonstrated these immunotherapeutics to elicit favourable antitumour responses in a variety of chemotherapy-refractory malignancies. However, use of these agents can also induce immune-related adverse events (irAEs) in off-target organs, including the heart and kidney. The most common manifestations of heart and kidney damage are myocarditis and acute interstitial nephritis, respectively, but other manifestations have been reported and, although rare, these off-target effects can be life threatening. Available data suggest that ICIs induce their off-target effects through several mechanisms, including direct binding to cell surface proteins expressed in healthy tissue, activation of T cells that cross-react with off-target tissues, generation of autoantibodies or by increasing levels of pro-inflammatory cytokines. Greater understanding of the adverse effects of cancer immunotherapies and the underlying mechanisms will facilitate the development of biomarkers to identify at-risk patients and approaches to prevent these irAEs.

Nephrotoxicity of Cancer Immunotherapies: Past, Present and Future.

Nephrotoxicity from cancer therapies is common and increasingly encountered in clinical practice, such that the subfield of "onco-nephrology" has emerged. Conventional chemotherapeutic drugs and novel agents targeting specific genes/proteins are effective cancer therapies but suffer from a number of adverse kidney effects. An effective avenue of cancer treatment is immunotherapy, which uses drugs that augment immune system-mediated recognition and targeting of tumor cells. As such, leveraging the immune system to target malignant cells represents an important modality in eradicating cancer. IFN and high-dose IL-2 are older immunotherapies used in clinical practice to treat various malignancies, whereas new cancer immunotherapies have emerged over the past decade that offer even more effective treatment options. The immune checkpoint inhibitors are an exciting addition to the cancer immunotherapy armamentarium. Chimeric antigen receptor T cells are also a new immunotherapy used to treat various hematologic malignancies. However, as with the conventional and targeted cancer agents, the immunotherapies are also associated with immune-related adverse effects, which includes nephrotoxicity.

Association of Acute Interstitial Nephritis With Programmed Cell Death 1 Inhibitor Therapy in Lung Cancer Patients.

Immune checkpoint inhibitors that target the programmed death 1 (PD-1) signaling pathway have recently been approved for use in advanced pretreated non-small cell lung cancer and melanoma. Clinical trial data suggest that these drugs may have adverse effects on the kidney, but these effects have not been well described. We present 6 cases of acute kidney injury in patients with lung cancer who received anti-PD-1 antibodies, with each case displaying evidence of acute interstitial nephritis (AIN) on kidney biopsy. All patients were also treated with other drugs (proton pump inhibitors and nonsteroidal anti-inflammatory drugs) linked to AIN, but in most cases, use of these drugs long preceded PD-1 inhibitor therapy. The association of AIN with these drugs in our patients raises the possibility that PD-1 inhibitor therapy may release suppression of T-cell immunity that normally permits renal tolerance of drugs known to be associated with AIN.

We use Continuous Renal Replacement Therapy for Overdoses and Intoxications.

Extracorporeal modalities for the removal of drugs and toxins are indicated for the treatment of overdoses and intoxications. Well-established modalities include hemodialysis (HD), high-flux HD (HfD), and charcoal hemoperfusion (HP). Recently, there have been increasing reports on the use of continuous renal replacement therapy (CRRT), such as continuous veno-venous hemodialysis (CVVHD), continuous veno-venous hemofiltration (CVVH) or CVVH combined with dialysis (CVVHDF). In the present article, we will discuss the various factors that determine the clearance of drugs and toxins and accordingly, we will propose that with few exceptions, CRRT does not have a role in the routine management of intoxications.

Drug-induced impairment of renal function.

Pharmaceutical agents provide diagnostic and therapeutic utility that are central to patient care. However, all agents also carry adverse drug effect profiles. While most of these are clinically insignificant, some drugs may cause unacceptable toxicity that impacts negatively on patient morbidity and mortality. Recognizing adverse effects is important for administering appropriate drug doses, instituting preventive strategies, and withdrawing the offending agent due to toxicity. In the present article, we will review those drugs that are associated with impaired renal function. By focusing on pharmaceutical agents that are currently in clinical practice, we will provide an overview of nephrotoxic drugs that a treating physician is most likely to encounter. In doing so, we will summarize risk factors for nephrotoxicity, describe clinical manifestations, and address preventive and treatment strategies.

Age-enhanced endoplasmic reticulum stress contributes to increased Atg9A inhibition of STING-mediated IFN-ß production during Streptococcus pneumoniae infection.

Pneumococcal infections remain a leading cause of death in persons ≥ 65 y of age. Recent reports have illustrated detrimental changes in the endoplasmic reticulum stress response or unfolded protein response in aging and age-related diseases; however, the relationship between aging, the unfolded protein response, and innate immune responses to Streptococcus pneumoniae has not been fully elucidated. Our results illustrate that stimulator of IFN genes-mediated production of IFN-ß during S. pneumoniae infection is decreased in aged hosts. Enhanced endoplasmic reticulum stress in response to S. pneumoniae augmented inositol-requiring protein 1/X-box binding protein 1-mediated production of autophagy-related gene 9 (Atg9a). Knockdown of Atg9a or treatment with gemcitabine HCl resulted in enhanced stimulator of IFN genes-mediated production of IFN-ß by aged macrophages. Consecutive treatments with gemcitabine during in vivo S. pneumoniae infection decreased morbidity and mortality in aged hosts, which was associated with decreased Atg9a expression, increased IFN-ß production, and improved bacterial clearance from lung tissue. Taken together, data presented in this study provide new evidence as to why older persons are more susceptible to S. pneumoniae, and provide a possible mechanism to enhance these responses, thereby decreasing morbidity and mortality in this population.

Tubulointerstitial injury associated with chemotherapeutic agents.

Chemotherapy holds tremendous potential in improving the survival of patients with cancer. However, the side effects of these drugs, including those that affect the kidney, can adversely affect patient outcomes. Prompt recognition of these adverse kidney effects allows early intervention that can minimize or prevent patient morbidity. In this review, we examine the nephrotoxic potential of chemotherapy drugs. In concentrating on tubulointerstitial injury, we will review common agents that result in acute kidney injury due to acute tubular necrosis, tubulopathies, crystal nephropathy, acute interstitial nephritis, and chronic interstitial nephritis, and we will present preventive and management strategies.