Interferon-?-associated focal segmental glomerulosclerosis with massive proteinuria in patients with chronic myeloid leukemia following high dose chemotherapy

Chapter 1: Evaluation of kidney function in patients undergoing anticancer drug therapy, from clinical practice guidelines for the management of kidney injury during anticancer drug therapy 2022

The prevalence of CKD may be higher in patients with cancer than in those without due to the addition of cancer-specific risk factors to those already present for CKD. In this review, we describe the evaluation of kidney function in patients undergoing anticancer drug therapy. When anticancer drug therapy is administered, kidney function is evaluated to (1) set the dose of renally excretable drugs, (2) detect kidney disease associated with the cancer and its treatment, and (3) obtain baseline values for long-term monitoring. Owing to some requirements for use in clinical practice, a GFR estimation method such as the Cockcroft-Gault, MDRD, CKD-EPI, and the Japanese Society of Nephrology's GFR estimation formula has been developed that is simple, inexpensive, and provides rapid results. However, an important clinical question is whether they can be used as a method of GFR evaluation in patients with cancer. When designing a drug dosing regimen in consideration of kidney function, it is important to make a comprehensive judgment, recognizing that there are limitations regardless of which estimation formula is used or if GFR is directly measured. Although CTCAEs are commonly used as criteria for evaluating kidney disease-related adverse events that occur during anticancer drug therapy, a specialized approach using KDIGO criteria or other criteria is required when nephrologists intervene in treatment. Each drug is associated with the different disorders related to the kidney. And various risk factors for kidney disease associated with each anticancer drug therapy.

Nephrotic-range proteinuria and membranoproliferative glomerulonephritis-like pattern caused by interferon-β1b in a patient with multiple sclerosis

Interferon-beta (IFN-β) subtypes are widely used as immunomodulatory agents for relapsing-remitting multiple sclerosis (MS). Although generally well tolerated, a growing number of reports have recently shown association of long-term IFN-β therapy with several types of glomerulonephritis. Here, we present the case of a 42-year-old woman with MS who developed nephrotic-range proteinuria after taking IFN-β1b for nine years. Initially, due to the presence of histological features consistent with immunoglobulin A (IgA) nephropathy (granular IgA deposits in mesangial lesions), a tonsillectomy plus steroid pulse therapy was performed. However, proteinuria did not significantly decrease after these treatments. Therefore, a second renal biopsy was performed after three years, revealing a membranoproliferative glomerulonephritis-like pattern without immune complex. Further immunofluorescence analysis showed attenuated IgA staining. Consequently, IFN-β1b was replaced with dimethyl fumarate, resulting in complete remission, with proteinuria decreasing to the level of 0.2 g/day. Although it is a rare adverse effect, physicians should pay careful attention to the symptoms and findings of nephritis during the follow-up of patients under treatment with this agent.

Immunotherapy-Related Acute Kidney Injury

Nephrotoxicity associated with immunotherapy is increasingly being encountered in clinical practice. Drugs that augment the immune system to eradicate cancer are revolutionary in the field of oncology. Older generation immunotherapies such as high-dose interleukin and interferon-alpha are now being replaced with more effective immune checkpoint inhibitors and chimeric antigen receptor T-cell therapies, which have shown promising results in numerous clinical trials. Unfortunately, these treatments come with a unique baggage of adverse effects including nephrotoxicity. This onconephrology review summarizes the immunotherapies currently in use and their kidney-related toxicities, pathophysiology, and their management.

Analysis of renal function during telaprevir-based triple therapy for chronic hepatitis C

Telaprevir (TVR) is used for the treatment of chronic hepatitis C in a combination therapy with pegylated-interferon and ribavirin. Although renal dysfunction is one of the critical adverse outcomes of this treatment, little is known regarding the mechanism of its onset. The present study assessed the association of renal function with TVR dose and viral response. Hematological, biochemical, urinary and virological parameters of renal function were examined during the TVR-based triple therapy of patients infected with hepatitis C virus (HCV) genotype 1b. Serum creatinine levels were increased and the estimated glomerular filtration rate (eGFR) was decreased in every patient during TVR administration, but these values recovered to normal levels following cessation of TVR. Fractional excretion of sodium was <1% at days 3 and 7, appearing similar regardless of baseline renal function. Urinary β₂-microglobulin levels were elevated and were significantly higher in patients with renal dysfunction, as compared with those not exhibiting renal dysfunction (P<0.05). The reduction in renal function was milder in patients treated with a reduced TVR dose, and these patients had a significantly lower risk of developing renal dysfunction (P<0.05). Using a multivariate analysis, TVR dose and eGFR at the initiation of treatment were identified as significant contributory factors in the development of renal dysfunction. Reduction in TVR dose did not lead to a significant increase in the viral kinetics of HCV or detrimental effects on the sustained viral response (SVR) rate. It is hypothesized that renal dysfunction during TVR treatment is caused by damage of the renal tubule, in addition to pre-renal dysfunction, and that reduction in TVR dose reduces the rate of renal dysfunction without causing a significant decrease in the SVR rate.

eGFR decrease during antiviral C therapy with first generation protease inhibitors: a clinical significance?

BACKGROUND & AIMS

Renal toxicity of first generation protease inhibitors (PIs) was not a safety signal in phase III clinical trials, but was recently reported in recent studies. It appeared important to determine the clinical significance of these findings.

METHODS

We retrospectively analysed 101 HCV patients receiving triple therapy with telaprevir (n = 36) or boceprevir (n = 26) or double therapy (n = 39) with peginterferon and ribavirin and having a close monitoring of eGFR (MDRD formula) during and after treatment. EGFR decline over time was assessed by a linear mixed-effects model (LMEM) with search for possible explanatory covariates.

RESULTS

Patients treated with telaprevir presented a significant decrease of eGFR with the same kinetics: initial decrease at W (week) 4, nadir at W8 (mean decrease 17.0 ± 18.9 ml/min/1.73 m(2)) and return to baseline at W16. The W8 eGFR was correlated with the D0 eGFR (R(2) = 0.49). The LMEM showed that interindividual variability in the slope of eGFR vs time between D0 and W8 was non-significant and eGFR nadir could be predicted from eGFR obtained at D0. In multivariate analysis, eGFR intercept (i.e. baseline value) was associated with older age and male sex.

CONCLUSION

The eGFR significantly varied in telaprevir group only. Our model showed that eGFR nadir mainly depended on initial eGFR. As telaprevir has been shown to inhibit mostly the drug transporter OCT2 which interacts with creatinine transport, the early decrease of eGFR observed could be a benign phenomenon. However, as unpredictable true renal toxicity may occur during therapy, we recommend a thorough follow-up of eGFR.

Nephrotic-range proteinuria on interferon-β treatment: immune-induced glomerulonephritis or other pathway?

We present a case report of a 37-year-old woman with multiple sclerosis (MS) who developed nephrotic-range proteinuria secondary to membrano proliferative glomerulonephritis (MPGN)-like disease with mesangial C3 deposition without evidence of immune-complex deposition in the context of long-term interferon-β (IFN-β) therapy. The complete remission of proteinuria following cessation of IFN-β, strongly suggests causality. To our knowledge, this is the second case report of MPGN associated with IFN-β use. This being the case, the negative immune screen, normal inflammatory markers and the absence of immune complex deposits would imply a different pathway to that previously suggested.

Acute tubular necrosis following interferon-based therapy for hepatitis C: case study with literature review

BACKGROUND/AIMS

Interferon treatment of malignant or viral diseases can be accompanied by various side-effects including nephro-toxicity.

METHODS

We report on a 68-year-old Caucasian male who received dual therapy with pegylated interferon 2a plus ribavirin for chronic hepatitis C.

RESULTS

After three months of antiviral therapy, the patient developed acute kidney failure (serum creatinine up to 6 mg/dL) with mild proteinuria (500 mg daily) and haematuria. Immediate immunosuppressive therapy with high-dose intravenous steroids did not improve kidney function. Kidney biopsy was consistent with acute tubular necrosis without glomerular abnormalities. He started long-term peritoneal dialysis (four regular exchanges) to provide both dialysis adequacy and ascites removal. Kidney function gradually improved over the following months (serum creatinine around 2 mg/dL) and peritoneal dialysis was continued with two exchanges daily. The temporal relationship between the administration of the drug and the occurrence of nephro-toxicity, and the absence of other obvious reasons for acute tubular necrosis support a causative role for pegylated interferon; benefit on kidney disease was noted after withdrawal of antiviral agents. An extensive review of the literature on acute tubular necrosis associated with interferon-based therapy, based on in vitro data and earlier case-reports, has been made. The proposed pathogenic mechanisms are reviewed.

CONCLUSIONS

Our case emphasizes the importance of monitoring renal function during treatment of chronic hepatitis C with antiviral combination therapy as treatment may precipitate kidney damage at tubular level.

Inhibition of type I interferon signalling prevents TLR ligand-mediated proteinuria

The mechanisms by which inflammation or autoimmunity causes proteinuric kidney disease remain elusive. Yet proteinuria is a hallmark and a prognostic indicator of kidney disease, and also an independent risk factor for cardiovascular morbidity and mortality. Podocytes are an integral component of the kidney filtration barrier and podocyte injury leads to proteinuria. Here we show that podocytes, which receive signals from the vascular space including circulating antigens, constitutively express TLR1–6 and TLR8. We find that podocytes can respond to TLR ligands including staphylococcal enterotoxin B (SEB), poly I:C, or lipopolysaccharide (LPS) with pro-inflammatory cytokine release and activation of type I interferon (IFN) signalling. This in turn stimulates podocyte B7-1 expression and actin remodelling in vitro and transient proteinuria in vivo. Importantly, the treatment of mice with a type I IFN receptor-blocking antibody (Ab) prevents LPS-induced proteinuria. These results significantly extend our understanding of podocyte response to immune stimuli and reveal a novel mechanism for infection- or inflammation-induced transient proteinuria. Dysregulation or aberrant activation of this response may result in persistent proteinuria and progressive glomerular disease. In summary, the inhibition of glomerular type I IFN signalling with anti-IFN Abs may be a novel therapy for proteinuric kidney diseases.

The antiviral cytokines IFN-α and IFN-β modulate parietal epithelial cells and promote podocyte loss: implications for IFN toxicity, viral glomerulonephritis, and glomerular regeneration

Interferon (IFN)-α and IFN-β are the central regulators of antiviral immunity but little is known about their roles in viral glomerulonephritis (eg, HIV nephropathy). We hypothesized that IFN-α and IFN-β would trigger local inflammation and podocyte loss. We found that both IFNs consistently activated human and mouse podocytes and parietal epithelial cells to express numerous IFN-stimulated genes. However, only IFN-β significantly induced podocyte death and increased the permeability of podocyte monolayers. In contrast, only IFN-α caused cell-cycle arrest and inhibited the migration of parietal epithelial cells. Both IFNs suppressed renal progenitor differentiation into mature podocytes. In Adriamycin nephropathy, injections with either IFN-α or IFN-β aggravated proteinuria, macrophage influx, and glomerulosclerosis. A detailed analysis showed that only IFN-β induced podocyte mitosis. This did not, however, lead to proliferation, but was associated with podocyte loss via podocyte detachment and/or mitotic podocyte death (mitotic catastrophe). We did not detect TUNEL-positive podocytes. Thus, IFN-α and IFN-β have both common and differential effects on podocytes and parietal epithelial cells, which together promote glomerulosclerosis by enhancing podocyte loss while suppressing podocyte regeneration from local progenitors.

Pathogenesis, diagnosis and management of paraneoplastic glomerulonephritis

Paraneoplastic glomerulonephritis is a rare complication of malignancy that is frequently mistaken for idiopathic glomerulonephritis. Failure to recognize paraneoplastic glomerulonephritis can subject patients to ineffective and potentially harmful therapy. The pathology of paraneoplastic glomerulonephritis varies between different types of malignancies. This Review discusses the association of glomerulonephritis with both solid tumors and hematological malignancies. The pathogenetic mechanisms of many glomerular lesions seem to relate to altered immune responses in the presence of a malignancy. Studies in the Buffalo/Mna rat model of spontaneous thymoma and nephrotic syndrome indicate that polarization of the immune response toward a T-helper-2 (T(H)2) profile has an important role in the development of thymoma-associated glomerular lesions. Furthermore, overexpression of the T(H)2 cytokine interleukin 13 in rats induces minimal change disease. Such findings from experimental studies might facilitate the identification of biomarkers that can distinguish paraneoplastic glomerulonephritis from idiopathic and other secondary glomerulonephritides. This Review describes potential pathogenetic mechanisms for paraneoplastic glomerulonephritides associated with different malignancies and highlights the need for a multidisciplinary approach to the management of patients with paraneoplastic glomerulonephritis.

Treatment with IFN-{alpha}, -{beta}, or -{gamma} is associated with collapsing focal segmental glomerulosclerosis

BACKGROUND AND OBJECTIVES

Treatment with IFN is rarely associated with nephrotic syndrome and renal biopsy findings of minimal-change disease or FSGS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We report 11 cases of collapsing FSGS that developed during treatment with IFN and improved after discontinuation of therapy.

RESULTS

The cohort consists of seven women and four men with a mean age of 48.2 yr. Ten of the 11 patients were black. Six patients were receiving IFN-alpha for hepatitis C virus infection (n = 5) or malignant melanoma (n = 1), three were receiving IFN-beta for multiple sclerosis, and two were treated with IFN-gamma for idiopathic pulmonary fibrosis. After a median and mean [corrected] duration of therapy of 4.0 and 12.6 months, respectively, patients presented with acute renal failure (mean creatinine 3.5 mg/dl) and nephrotic-range proteinuria (mean 24-hour urine protein 9.7 g). Renal biopsy revealed collapsing FSGS with extensive foot process effacement and many endothelial tubuloreticular inclusions. Follow-up was available for 10 patients, all of whom discontinued IFN. At a mean of 23.6 months, nine of 10 patients had improvement in renal function, including one with complete remission and two with partial remission. Among the seven patients with available data, mean proteinuria declined from 9.9 to 3.0 g/d. Four of the seven patients were treated with immunosuppression, and there was no detectable benefit.

CONCLUSIONS

Collapsing FSGS may occur after treatment with IFN-alpha, -beta, or -gamma and is typically accompanied by the ultrastructural finding of endothelial tubuloreticular inclusions. Optimal therapy includes discontinuation of IFN.

HIV-associated nephropathy: clinical presentation, pathology, and epidemiology in the era of antiretroviral therapy

The classic kidney disease of human immunodeficiency virus (HIV) infection, HIV-associated nephropathy, is characterized by progressive acute renal failure, often accompanied by proteinuria and ultrasound findings of enlarged, echogenic kidneys. Definitive diagnosis requires kidney biopsy, which shows collapsing focal segmental glomerulosclerosis with associated microcystic tubular dilatation and interstitial inflammation. Podocyte proliferation is a hallmark of HIV-associated nephropathy, although this classic pathology is observed less frequently in antiretroviral-treated patients. The pathogenesis of HIV-associated nephropathy involves direct HIV infection of renal epithelial cells, and the widespread introduction of combination antiretroviral therapy has had a significant impact on the natural history and epidemiology of this unique disease. These observations have established antiretroviral therapy as the cornerstone of treatment for HIV-associated nephropathy in the absence of prospective clinical trials. Adjunctive therapy for HIV-associated nephropathy includes angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers, as well as corticosteroids in selected patients with significant interstitial inflammation or rapid progression.

The spectrum of focal segmental glomerulosclerosis: new insights

PURPOSE OF REVIEW

Focal segmental glomerulosclerosis (FSGS) is a disease with diverse histologic patterns and etiologic associations. Genetic, toxic, infectious and inflammatory mediators have been identified. This review will focus on new evidence supporting the potential mechanistic basis underlying the histologic variants and their clinical relevance.

RECENT FINDINGS

Evidence from animal models and in-vitro studies suggests that injury inherent within or directed to the podocyte is a central pathogenetic factor. Disruption of signaling from any of the podocyte's specialized membrane domains, including slit diaphragm, apical and basal membranes, or originating at the level of the actin cytoskeleton, may promote the characteristic response of foot process effacement. Irreversible podocyte stress leading to podocyte depletion through apoptosis or detachment is a critical mechanism in most forms of FSGS. In the collapsing variant, podocyte dysregulation leads to podocyte dedifferentiation and glomerular epithelial cell proliferation.

SUMMARY

Translation studies in humans and new evidence from animal models have provided mechanistic insights into the diverse phenotypes of FSGS.

Renal disease in patients with cancer

Kidney disease is very common in patients with cancer. Nephrologists are vital members of the multidisciplinary care team for these patients. Given the high prevalence of comorbidities in patients treated for active malignancy, it is not surprising that these individuals frequently develop renal diseases that are common among other hospitalized patients, such as those arising from sepsis, hypotension or use of nephrotoxic agents (e.g. radiocontrast or antimicrobial agents). The role of the nephrologist in these cases differs little with respect to the presence or absence of cancer. On the other hand, there are several renal syndromes that are unique to patients with cancer, being caused either by the cancer itself or by its treatment. These syndromes are reviewed here. In addition, patients who are receiving chemotherapy often require dialysis for either acute or chronic kidney disease. Unfortunately, there is very little information on the clearance characteristics of most chemotherapeutic agents. In cancer patients with renal disease, both the timing of administration and the dose-adjustment of chemotherapy must rely on clinical experience and close clinical observation.

Immunomodulators: interleukins, interferons, and IV immunoglobulin

The outstanding progress in immunology and the development of new technologies have resulted in the introduction of new immunotherapies, the so-called “immunomodulators”, for autoimmune diseases, inflammatory disorders, allograft rejection, and cancer. These immunomodulators comprise recombinant cytokines and specific blocking or depleting antibodies. Many of these therapies achieve their effect by stimulating the release of cytokines. The term cytokines includes interleukins (IL-), chemokines, growth factors, interferons (IFN), colony stimulating factors (CSF), and tumor necrosis factors (TNF). These molecules are involved in inflammation, cell proliferation and apoptosis, tissue injury and repair.

These new therapeutic tools can be associated with side effects among which nephrotoxicity. The most common immunomodulators associated with nephrotoxicity are described in Table 1. The nephrotoxic side effects of immunomodulators can be roughly divided into (ischemic) tubular necrosis, thrombotic microangiopathy, serum sickness, and autoimmune disorders.

Drug-induced glomerulopathies

Normal renal function depends upon an intact glomerular apparatus. Many drugs and chemicals are capable of damaging the glomerulus, causing its increased permeability to large molecules. Glomerular lesions are usually responsible for proteinuria and the nephrotic syndrome. This also holds true for the drug-induced glomerulopathies, of which membranous glomerulo-nephritis is the most frequent type of lesion encountered. Apart from this, several cases of different glomerular changes such as focal segmental glomerulosclerosis and crescentic glomerulonephritis have also been reported. The drug-induced glomerulopathies are probably immune mediated. This is, for instance, reflected in the fact that patients with drug-induced nephritic syndrome frequently have the HLA-B8 and DR3 antigens. In depth information is provided for the previously mentioned disorders.

Hypocalcemia and Azotemia Associated with Zoledronic Acid and Interferon Alfa

OBJECTIVE

To describe severe hypocalcemia and acute renal failure associated with zoledronic acid and interferon alfa in a patient with metastatic carcinoid tumors.

CASE SUMMARY

A 39-year-old white man with metastatic carcinoid tumor tolerated treatment with subcutaneous long-acting octreotide monthly and interferon alfa 6 million units 3 times weekly for 6 months. Due to multiple bony metastases, zoledronic acid was prescribed as a monthly 4-mg intravenous infusion over 30 minutes to prevent skeletal-related events. Although the first infusion went well, the patient developed severe hypocalcemia and acute renal failure after the second zoledronic infusion.

DISCUSSION

Bisphosphonates may infrequently cause symptomatic hypocalcemia, especially among patients who have vitamin D deficiency or hypoparathyroidism or receive treatment with an aminoglycoside. Our literature review suggests that zoledronic acid and interferon alfa may exert additive effects on the inhibition of osteoclasts, thus potentially precipitating hypocalcemia. Renal dysfunction may not be a direct consequence of interferon alfa. However, altered mental function due to hypocalcemia may lead to dehydration and further exacerbate renal dysfunction, a known adverse effect of zoledronic acid. Since therapeutic indications of both interferon alfa and zoledronic acid continue to expand, clinicians should be aware of these serious adverse reactions and potential interaction. Supportive treatment with hydration, calcium supplement, and oral calcitriol resulted in resolution of hypocalcemia, but only partial improvement of azotemia.

CONCLUSIONS

In our patient with metastatic carcinoid tumor, treatment with zoledronic acid and interferon alfa was associated with symptomatic hypocalcemia and acute renal failure.

Interferon-alpha-induced focal segmental glomerulosclerosis in chronic myelogenous leukemia: a case report and review of the literature

Chronic myelogenous leukemia (CML), hepatitis C, and interferon alpha (IFNalpha) have all been associated with renal dysfunction. In this paper we present a patient with the diagnosis of nephrotic syndrome and a known history of hepatitis C who received IFNalpha therapy for newly diagnosed CML. The renal biopsy showed focal segmental glomerulosclerosis, which has only been previously reported in two cases of CML treated with IFNalpha. There have also been two cases of patients with hepatitis C associated with focal segmental glomerulosclerosis. Despite the underlying hepatitis C, this case represents renal abnormalities consistent with IFNalpha therapy for CML.

Withdrawal of interferon-alpha results in prompt resolution of thrombocytopenia and hemolysis but not renal failure in hemolytic uremic syndrome caused by interferon-alpha

This case report describes 2 patients with chronic myeloid leukemia in whom hemolytic uremic syndrome developed while being treated with interferon-alpha and hydroxycarbamide. Hemolytic uremic syndrome was recognized by progressive renal dysfunction, thrombocytopenia, microangiopathic hemolytic anemia, and histologic features of thrombotic microangiopathy in the kidney. Although renal dysfunction progressed to dialysis-dependent renal failure in one patient despite treatment with prednisolone and plasmapheresis but not in other, withdrawal of the treatment resulted in a prompt resolution of thrombocytopenia and microangiopathic hemolytic anemia in both patients.

Immune-mediated complications during interferon therapy in hematological patients

Interferon (IFN), a leukocyte-derived cytokine, has been used to treat several hematological malignancies. The most common adverse effects of IFN are flu-like symptoms. Autoimmune side effects are infrequent but may be hazardous and irreversible. These may occur in several ways: autoantibodies may either appear during the treatment or existing titers may rise, subclinical autoimmune phenomena may become clinically manifest or autoimmune diseases may appear de novo. The main categories of IFN immune-mediated side effects are: thyroid, hematological, connective tissue, renal and miscellaneous disorders. The most common ones are thyroid disorders, which manifest either as hypo- or hyperthyroidism. Patients with pre-existing autoantibodies are more susceptible to the exacerbation of thyroid autoimmunity, probably since IFN enhances the levels of autoimmunity. Hematological disorders include autoimmune anemia and thrombocytopenia and thrombotic thrombocytopenic purpura. The immunological derangement of autoimmune hemolytic anemia manifests as enhanced destruction of antibody-coated red blood cells and induction of autoreactive B cells secreting these antibodies. Although autoimmune thrombocytopenia is rare, a sharp reduction in the platelet counts, beyond that expected from the antiproliferative effects of IFN, should raise this possibility. Thrombotic thrombocytopenic purpura has recently been included among the autoimmune disorders. Sporadic cases have been reported in association with IFN treatment. The clinical spectrum of IFN-induced connective tissue disorders ranges from typical systemic lupus erythematosus to seropositive or seronegative rheumatoid arthritis. Some authors also reported on the development of Behçet's disease in chronic myeloid leukemia patients treated with IFN. The underlying reason for the skin hyperreactivity in Behçet's disease and the effect of IFN treatment in these patients may be altered neutrophil activity in both disorders. Several series evaluated the incidence of Raynaud's phenomenon in patients treated with IFN for hematological disorders. Some of them reported on a rather high incidence of nailfold capillary microscopy abnormalities with or without Raynaud's phenomenon. Whether IFN-induced Raynaud's phenomenon is immune-mediated or directly caused vasospasm, is still unknown although the occurrence of several autoantibodies suggests an immune mechanism. Adverse effects of IFN therapy on the kidney include proteinuria and rarely nephrotic syndrome or acute and chronic renal failure. The mechanism of renal injury is unclear although an immune mechanism is suggested. Sporadic cases of other immune-mediated side effects have been published. These include dermatological adverse effects manifesting as psoriasis, pemphigus and vitiligo, and also rare cases of sarcoidosis, hepatitis, colitis or cryoglobulinemia. In conclusion, patients treated with IFN should be monitored for symptoms of autoimmunity. Patients with previous autoimmune phenomena should be treated, if possible, with alternative drugs since there is risk of exacerbation of these manifestations in these patients.

Recent developments in toxic nephropathy

Toxic nephropathy is an important cause of reversible renal injury if detected early. Renal damage can be due to several different mechanisms affecting different segments of the nephron, renal microvasculature or interstitium. Clinical signs may not be apparent in the early stages and assessment of renal function should include thorough evaluation of glomerular filtration rate, proximal and distal tubular function. A kidney biopsy may be indicated to establish the cause and effect relationship. The presence of comorbid conditions such as older age, diabetes mellitus, hypertension and congestive heart failure have a significant influence on the patient's ability to recover from the toxic effects. A significant degree of drug-induced renal toxicity is only acceptable if the causative agent is used for the curative treatment of an underlying disease but not if the aim is the palliative or supportive therapy. The decision to reduce the dose or to stop the toxic agent must be based on the ultimate goal of therapy and the patient's baseline health status.

Interferon therapy in primary care

Interferons are proteins produced by human blood cells in response to stimulation (viral infection). The natural roles of interferons are host defense and modulation of the immune system. Therapeutic uses are based on these roles. Interferon-alpha has been widely used for malignancies, skin conditions, viral infections, and myeloproliferative disorders. Interferon-beta is a standard treatment for relapsing multiple sclerosis. Interferon-gamma therapy is currently used for chronic granulomatous disease and skin lesions (human papilloma virus related and keloids), but further research is ongoing. Side effects of interferon therapy are common and limit utility. Flulike symptoms are reported by more than 75% and depression by 10-40% of interferon users. Severe adverse effects are less common but may be life threatening, including autoimmune diseases, thrombotic-thrombocytopenic purpura, and acute renal failure. Limited use of interferon therapy during pregnancy has been described, with successful maternal and neonatal outcomes. Use of interferon therapy during early pregnancy is not an indication for termination.

High-dose cytosine arabinoside and idarubicin treatment of chronic myeloid leukemia in myeloid blast crisis

Chronic myeloid leukemia in myeloid blast crisis (CML-MBC) is highly resistant to standard induction chemotherapy regimens. Anecdotal results from previous clinical trials support the concept of dose escalation in patients with CML-MBC. Eight patients with CML-MBC were treated with cytosine arabinoside (Ara-C) 1.5-3.0 g/m2 intravenously over 1 hr every 12 hr for 12 doses and idarubicin 12 mg/m2 intravenously daily for 3 days. Sixteen previous reports describing the use of Ara-C-based chemotherapy regimens in patients with CML-MBC were also reviewed. Our patients' median age was 62 years (range, 42-69 years). One patient achieved complete hematologic remission (95% confidence interval, 0.3%, 53%). The median survival for our patients was 7.3 months. These results were not different from previous published reports using Ara-C-based chemotherapy regimens to treat CML-MBC. In summary, the combination of high-dose Ara-C and idarubicin did not improve the overall prognosis of patients with CML-MBC. Innovative approaches need to be explored for this patient population.