Nephrotoxicity of ifosfamide--moving towards understanding the molecular mechanisms

The link between kidney disease and cancer: complications and treatment

Acute and chronic kidney disease encompasses a complex set of diseases that can both lead to, and result from, cancer. In particular, kidney disease can arise from the use of chemotherapeutic agents. Many of the current and newly developed cancer chemotherapeutic agents are nephrotoxic and can promote kidney dysfunction, which frequently manifests during the terminal stages of cancer. Given the link between kidney disease and cancer development and treatment, the aim of this Review is to highlight the importance of multidisciplinary collaboration between oncologists and nephrologists to predict and prevent chemotherapeutic-induced nephrotoxicity. As new therapies are introduced to treat cancer, new renal toxicities require proper diagnosis and management. We anticipate that multidisciplinary collaborations will lead to the development and implementation of guidelines for clinicians to improve the therapeutic management of patients with both cancer and renal impairment.

[Ifosphamide nephrotoxicity]

Ifosfamide is a cytotoxic drug usually used in malignant sarcomas. The nephrotoxicity of this agent has been described essentially among children, revealed by renal failure and proximal tubulopathy. We recently conducted a retrospective multicentre study, describing 34 adult patients admitted for ifosfamide nephrotoxicity. More than 80% of them presented with renal failure, diagnosed up to 48 months after ifosfamide administration. A Fanconi syndrome with hypophosphoremia, hypokaliemia, glucosuria and low-molecular weight proteinuria, was present in two third of all cases. Median estimated glomerular filtration rate was 31mL/min 1 month and 38mL/min 3 months after ifosfamide infusion, versus 67mL/min at baseline. Renal biopsy, performed in 14 of these patients, showed acute tubular necrosis with vacuolization of proximal tubular epithelial cells with marked nuclear modifications, whereas electron microscopy revealed major changes of mitochondrial structure inside those cells, suggesting a tenofovir-like mechanism of nephrotoxicity. After a median follow-up of 31 months, ten patients out of 34 reached stage 5 chronic kidney disease, requiring dialysis in five cases. Poor renal prognosis was associated with concomitant cisplatin use (P=0.02) and with older age at presentation (P=0.04). In conclusion, ifosfamide nephrotoxicity is often severe and irreversible, leading to proximal tubulopathy and sometimes-severe chronic kidney failure, that can be immediate or delayed, sometimes diagnosed months after chemotherapy completion.

Evaluation of ifosfamide salvage therapy for metastatic canine osteosarcoma

A retrospective study was performed to assess toxicity and response rate of ifosfamide salvage treatment for dogs diagnosed with metastatic osteosarcoma (OSA). Dogs diagnosed with OSA and previously treated with standard chemotherapy were included in the study. Nineteen dogs met the inclusion criteria, and 17 dogs were evaluable for response. Ifosfamide doses ranged from 375 to 425 mg m(-2) (median dose 375 mg m(-2)), with a median of two doses administered per dog (range 1-7 doses). The overall response to ifosfamide was 11.8% [complete response (CR) = 1/17, partial response (PR) = 1/17, stable disease (SD) = 2/17, progressive disease (PD) = 13/17]. Two dogs were hospitalized due to ifosfamide toxicosis. The median survival duration from the first dose of ifosfamide to death was 95 days. Ifosfamide was well tolerated, but minor anti-tumour activity was observed.

Osteomalacia as a late metabolic complication of Ifosfamide chemotherapy in young adults: illustrative cases and review of the literature

Purpose. Ifosfamide is a drug commonly used in the management of sarcomas and other solid tumours. One potential toxicity of its use is renal tubular damage, which can lead to skeletal abnormalities; rickets in children and osteomalacia in adults. We aimed to characterise this rare complication in adults. Patients. Three illustrative patient cases treated in our institution are presented. All were treated for sarcoma, and received varying doses of ifosfamide during their therapy. Methods. We performed a review of the literature on the renal tubular and skeletal complications of ifosfamide in adults. Papers were identified by searches of PubMed using the terms "osteomalacia," "nephrotoxicity," "Fanconi syndrome," "ifosfamide," and "chemotherapy" for articles published between 1970 and 2006. Additional papers were identified from review of references of relevant articles. Results. There are only four case reports of skeletal toxicity secondary to ifosfamide in adults; the majority of data refer to children. Risk factors for development of renal tubular dysfunction and osteodystrophy include platinum chemotherapy, increasing cumulative ifosfamide dose, and reduced nephron mass. The natural history of ifosfamide-induced renal damage is variable, dysfunction may not become apparent until some months after treatment, and may improve or worsen with time. Discussion. Ifosfamide-induced osteomalacia is seldom described in adults. Clinicians should be vigilant for its development, as timely intervention may minimise complications.

New clues for nephrotoxicity induced by ifosfamide: preferential renal uptake via the human organic cation transporter 2

Anticancer treatment with ifosfamide but not with its structural isomer cyclophosphamide is associated with development of renal Fanconi syndrome leading to diminished growth in children and bone problems in adults. Since both cytotoxics share the same principal metabolites, we investigated whether a specific renal uptake of ifosfamide is the basis for this differential effect. First we studied the interaction of these cytotoxics using cells transfected with organic anion or cation transporters and freshly isolated murine and human proximal tubules with appropriate tracers. Next we determined changes in membrane voltage in proximal tubular cells to understand their differentiated nephrotoxicity. Ifosfamide but not cyclophosphamide was significantly transported into cells expressing human organic cation transporter 2 (hOCT2) while both did not interact with organic anion transporters. This points toward a specific interaction of ifosfamide with hOCT2, which is the main OCT isoform in human kidney. In isolated human proximal tubules ifosfamide also interacted with organic cation transport. This interaction was also seen in isolated mouse proximal tubules; however, it was absent in tubules from OCT-deficient mice, illustrating the biological importance of this selective transport. Ifosfamide decreased the viability of cells expressing hOCT2, but not that of control cells. Coadministration of cimetidine, a known competitive substrate of hOCT2, completely prevented this ifosfamide-induced toxicity. Finally, ifosfamide but not cyclophosphamide depolarized proximal tubular cells. We propose that the nephrotoxicity of ifosfamide is due to its selective uptake by hOCT2 into renal proximal tubular cells, and that coadministration of cimetidine may be used to prevent ifosfamide-induced nephrotoxicity.

Nephrotoxicity of cancer treatment in children

Chronic renal impairment in children with cancer may be caused by the malignant process itself or result from adverse effects of treatment including cytotoxic drugs, radiotherapy, surgery or supportive treatment. Although severe renal chronic disease is uncommon, occurring in only 0.8% of long-term survivors of childhood cancer, 1.9% of all cases of established renal failure are due to malignancy and 0.8% to drug nephrotoxicity. The relative risk of severe renal chronic disease (compared with siblings) is 8.1, and that of renal failure or the need for dialysis is 8.9. The cytotoxic drugs most likely to cause important chronic nephrotoxicity are ifosfamide and cisplatin, both of which are used widely in many solid tumors and may cause chronic glomerular and/or renal tubular toxicity in 30–60% of treated children. Significant renal toxicity is less frequent with other chemotherapeutic drugs, but may result from treatment with carboplatin, methotrexate and nitrosoureas. Other cytotoxic drugs occasionally cause specific patterns of glomerular or tubular toxicity in children. Partial or unilateral nephrectomy leads to hypertrophy and hyperfiltration of the remaining renal tissue, and may result in microalbuminuria, hypertension and in rare cases, chronic renal impairment. Radiotherapy to a field including renal tissue may cause late onset chronic renal damage, manifest by hematuria, proteinuria, hypertension and anemia, sometimes progressing to chronic renal failure. Chronic nephrotoxicity is also common in survivors of hemopoietic stem cell transplantation, and is often multifactorial with contributions from prior chemotherapy, total body irradiation, immunosuppressive drugs and transplant complications, such as infection or hemorrhage. Patients at risk of renal damage should be monitored regularly with a defined surveillance protocol to enable timely management. General measures often employed to prevent or reduce nephrotoxicity include the use of intravenous hydration during drug administration and avoidance of known risk factors, such as high drug doses. Although numerous potentially nephroprotective drugs have been suggested and investigated, none have yet been introduced into clinical use in children due to the lack of proven efficacy. Improved understanding of the pathogenesis of nephrotoxicity is necessary to reduce the frequency and severity of this potentially serious complication of treatment in children with cancer.

Advances in urinary proteome analysis and biomarker discovery in pediatric renal disease

Recent progress in proteomic analysis and strategies for the identification of clinically useful biomarkers in biofluids has led to the identification of urine as an excellent non-invasive reservoir for biomarkers of disease. Urinary biomarkers have been identified and validated on independent cohorts in different high-incidence adult renal diseases, including diabetic nephropathy, chronic kidney disease and immunoglobulin A-nephropathy, but also in extrarenal disease, such as coronary artery disease. Unfortunately, this type of research is underrepresented in the pediatric population. Here, we present the rare studies in the pediatric population that identified potential clinically useful urinary biomarkers in ureteropelvic junction (UPJ) obstruction and renal Fanconi syndrome. These studies, although limited in number, clearly show the potential of urinary proteomics, especially in the pediatric population. It is anticipated that the advances made in the adult population, the lessons learned on the use of appropriate statistics and the inclusion of independent blinded validation cohorts in these types of studies will rapidly lead to clinical useful urinary biomarkers for other pediatric (renal) disease in a population where non-invasive analysis is particularly appreciated.

Ifosfamide nephrotoxicity in children: a mechanistic base for pharmacological prevention

The antineoplastic drug ifosfamide (IFO) in the treatment of solid tumors, particularly in children, is the cause of severe nephrotoxicity. Although it is a potent and effective chemotherapeutic agent, the associated nephrotoxicity has a serious impact on the health and the quality of life of exposed children. The toxic metabolite of IFO thought to be responsible for IFO-induced kidney damage is chloroacetaldehyde (CAA). Those suffering from nephrotoxicity typically develop tubular and glomerular toxicities, with the most severe form being Fanconi's syndrome. As the mode of toxicity of CAA seems to be primarily owing to oxidative stress, the use of antioxidants as a protective measure for the kidneys is a promising strategy. In this review, we highlight recent research that supports the local renal production of CAA as the proximate cause of IFO-induced nephrotoxicity with age as an important risk factor, those under the age of three being the most vulnerable. Most importantly, we focus on the potential advantages of the antioxidant N-acetylcysteine owing to both its antioxidant properties and its current use clinically in pediatrics.

Urinary proteome pattern in children with renal Fanconi syndrome

BACKGROUND

The renal Fanconi syndrome (FS) is characterized by renal glucosuria, loss of electrolytes, bicarbonate and lactate, generalized hyperaminoaciduria and low-molecular-weight proteinuria. We studied the urinary low-molecular-weight proteome to identify excreted peptides indicative of a pathogenetic mechanism leading to tubular dysfunction.

METHODS

We established a urinary proteome pattern using capillary electrophoresis mass spectrometry (CE-MS) of 7 paediatric patients with cystinosis and 6 patients with ifosfamide-induced FS as the study group, and 54 healthy volunteers and 45 patients suffering from other renal diseases such as lupus nephritis (n = 8), focal segmental glomerulosclerosis (n = 27), minimal change disease (n = 7) and membranous glomerulonephritis (n = 3) as controls. Consequently, we conducted a blinded study consisting of 11 FS patients and 9 patients with renal disease other than FS. Additionally, we applied this pattern to 294 previously measured samples of patients with different renal diseases. Amino acid sequences of some marker proteins were obtained.

RESULTS

Specificity for detecting FS was 89% and sensitivity was 82%. The marker peptides constituting the proteome pattern are fragments derived from osteopontin, uromodulin and collagen alpha-1.

CONCLUSIONS

CE-MS can be used to diagnose FS in paediatric patients and might be a future tool for the non-invasive diagnosis of FS. The reduced amount of the marker proteins osteopontin and uromodulin indicates loss of function of tubular excretion in all patients suffering from FS regardless of the underlying cause. In addition, the six different fragments of the collagen alpha-1 (I) chain were either elevated or reduced in the urine. This indicates a change of proteases in collagen degradation as observed in interstitial fibrosis. These changes were prominent irrespectively of the stages of FS. This indicates fibrosis as an early starting pathogenetic reason for the development of renal insufficiency in FS patients.

The pharmacologic basis of ifosfamide use in adult patients with advanced soft tissue sarcomas

The treatment outcome of patients with locally advanced and metastatic soft tissue sarcomas is poor. Doxorubicin is regarded as standard treatment, but its use is featured by the occurrence of cardiotoxicity. This hinders the administration of this drug at high doses or in combination with, in theory, attractive newly developed targeted drugs, such as vascular endothelial growth factor (VEGF) pathway inhibitors. The combination of doxorubicin and VEGF pathway inhibitors has been shown to yield an unacceptable high rate of cardiomyopathy. Ifosfamide is the only drug that consistently shows response rates comparable to those of doxorubicin. The lack of cardiotoxicity renders this drug a much more attractive alternative than doxorubicin to be explored at high doses or as part of new drug combinations. This review addresses the clinical pharmacology, metabolism, and present role of ifosfamide in the treatment of locally advanced and/or metastatic soft tissue sarcomas, excluding gastrointestinal stromal tumors, the Ewing-like sarcomas, and other small blue round cell tumors. Furthermore, this review focuses on the anticipated growing role of ifosfamide in the development of new treatment strategies.

Ifosfamide metabolites CAA, 4-OH-Ifo and Ifo-mustard reduce apical phosphate transport by changing NaPi-IIa in OK cells

Renal Fanconi syndrome occurs in about 1-5% of all children treated with Ifosfamide (Ifo) and impairment of renal phosphate reabsorption in about 20-30% of them. Pathophysiological mechanisms of Ifo-induced nephropathy are ill defined. The aim has been to investigate whether Ifo metabolites affect the type IIa sodium-dependent phosphate transporter (NaPi-IIa) in viable opossum kidney cells. Ifo did not influence viability of cells or NaPi-IIa-mediated transport up to 1 mM/24 h. Incubation of confluent cells with chloroacetaldehyde (CAA) and 4-hydroperoxyIfosfamide (4-OH-Ifo) led to cell death by necrosis in a concentration-dependent manner. At low concentrations (50-100 microM/24 h), cell viability was normal but apical phosphate transport, NaPi-IIa protein, and -mRNA expression were significantly reduced. Coincubation with sodium-2-mercaptoethanesulfonate (MESNA) prevented the inhibitory action of CAA but not of 4-OH-Ifo; DiMESNA had no effect. Incubation with Ifosfamide-mustard (Ifo-mustard) did alter cell viability at concentrations above 500 microM/24 h. At lower concentrations (50-100 microM/24 h), it led to significant reduction in phosphate transport, NaPi-IIa protein, and mRNA expression. MESNA did not block these effects. The effect of Ifo-mustard was due to internalization of NaPi-IIa. Cyclophosphamide-mustard (CyP-mustard) did not have any influence on cell survival up to 1000 microM, but the inhibitory effect on phosphate transport and on NaPi-IIa protein was the same as found after Ifo-mustard. In conclusion, CAA, 4-OH-Ifo, and Ifo- and CyP-mustard are able to inhibit sodium-dependent phosphate cotransport in viable opossum kidney cells. The Ifo-mustard effect took place via internalization and reduction of de novo synthesis of NaPi-IIa. Therefore, it is possible that Ifo-mustard plays an important role in pathogenesis of Ifo-induced nephropathy.

Effect of squalene on cyclophosphamide-induced toxicity

BACKGROUND

Toxicity due to drugs used for neoplastic disorders is extensively documented. Cyclophosphamide (CYP) is a widely used antineoplastic drug, which could cause toxicity of normal cells due to its toxic metabolites. We evaluated the protective role of squalene (SQ) in the toxicity induced by cyclophosphamide.

METHODS

The activities of serum marker enzymes, clinical chemistry parameters and histopathology studies were done according to the standard procedures in the control and experimental groups of rats.

RESULTS

Toxicity of the organs like heart, kidney and liver was evidenced from significant (P<0.05) increases of CK, LDH, AST, ALT, ALP, urea, creatinine and total bilirubin in cyclophosphamide- (150 mg/kg for 2 days) administered rats. Abnormal activities of these enzymes in the organs and serum total protein and cholesterol were also observed. No significant changes were observed in triglycerides in serum. Squalene oral treatment exerted protection towards these organs at a dose of 0.4 ml/day/rat. Histopathological examinations also confirmed the protective efficacy of squalene.

CONCLUSION

Squalene may be efficacious as a cytoprotectant in cyclophosphamide-induced toxicities.

Delaying surgery with chemotherapy for osteosarcoma of the extremities

Osteosarcoma is the most frequent primary cancer of bone. When treated by surgery alone, it is almost invariably followed by metastatic dissemination and death. This dismal prognosis can be improved dramatically by including chemotherapy in an interdisciplinary regimen. Today, two-thirds of patients with localised extremity primaries can achieve long-term survival with such intensive multimodal therapy. This article provides a summary overview of current pharmacotherapy in osteosarcoma of the extremities, focussing on the approach of preoperative 'neoadjuvant' chemotherapy and thus, the potential benefits and pitfalls of delaying surgery. Prospective, multi-institutional trials are essential in guaranteeing that as many patients as possible can benefit from modern, efficacious interdisciplinary therapeutic regimens and that further progress can be made.

Influence of age upon Ifosfamide-induced nephrotoxicity

BACKGROUND

Ifosfamide-induced nephrotoxicity is well recognized in children, although it has also been reported in adults. Whether ifosfamide nephrotoxicity is more common in children than in adults is not known.

PROCEDURE

Medical records of adults and children diagnosed with sarcoma whom received ifosfamide with a cumulative dose >20 g/m(2) were evaluated. Twenty-five children (</=18-years of age) and 28 adults were identified.

RESULTS

National Cancer Institute Common Toxicity Criteria grade 3-4 ifosfamide-induced nephrotoxicity was present in 24 and 17% of children and adults, respectively (P = 0.58). Cumulative ifosfamide doses were similar between the two populations, with the median (range) of 70.2 g/m(2) (22.4-72) for children and 59 g/m(2) (20.8-146) for adults (P = 0.25). Logistic regression analysis indicated that neither age or cumulative ifosfamide dose were associated with grade 3-4 ifosfamide-induced nephrotoxicity (P = 0.36).

CONCLUSIONS

Children and adults receiving >20 g/m(2) of ifosfamide have similar susceptibility to ifosfamide-induced nephrotoxicity. Factors other than age and cumulative dose should be considered for understanding the inter-individual variation in nephrotoxicity.

Chronic ifosfamide nephrotoxicity in children

Nephrotoxicity is a frequent complication of treatment with ifosfamide in children. Although renal damage may be acute and reversible, chronic toxicity may develop with potentially serious consequences. Chronic nephrotoxicity due to ifosfamide may lead to a wide variety of subclinical and clinical manifestations. Proximal tubular dysfunction is the commonest presentation, and may lead to a Fanconi syndrome, including hypophosphataemic rickets and proximal renal tubular acidosis. Glomerular impairment is also common, whilst distal tubular impairment has been described but is relatively rare. Although full reversibility has been described occasionally, there is no information about the very long-term outcome of chronic ifosfamide nephrotoxicity. We studied a cohort of 12 children 1 and 10 years after completion of ifosfamide treatment. There was no statistically significant change in either glomerular or tubular toxicity in the group as a whole over this time period. However, marked improvements were seen in some aspects of toxicity in some patients, and deterioration was observed in others. We concluded that considerable nephrotoxicity is still present 10 years after completion of ifosfamide treatment, but that the outcome varies between individual patients. Although several risk factors for the development of chronic nephrotoxicity have been described, total ifosfamide dose, patient age at treatment, previous or concurrent cisplatin treatment, and unilateral nephrectomy are the most important. Nevertheless, it remains difficult to predict the occurrence of this toxicity with confidence. The pathogenesis of ifosfamide nephrotoxicity is poorly understood. There is an urgent need for the development and clinical investigation of nephroprotective strategies.

Renal function following hematological stem cell transplantation in childhood

Renal function greatly influences mortality rates in the early phase following hematological stem cell transplantation (HSCT) in childhood, as well as the quality of life in long-term survivors. Nevertheless, the number of studies in pediatric populations is limited and some important aspects of kidney function after HSCT have only been elucidated in adults. The incidence of acute renal failure (ARF) immediately after HSCT in pediatric patients is between 25% and 50%, with 5%-10% of children requiring renal replacement therapy. Doubling of serum creatinine is associated with a twofold increase in mortality. However, the need for dialysis leads to a further increase in mortality rates to 80%-90%. Specific renal syndromes appear at different times following HSCT, revealing a similar pattern in children and adult patients. In both children and adults, impaired renal function associated with liver impairment (hepatorenal syndrome) is the most important cause for ARF. Therapeutic approaches have not been able to reduce the frequency or to improve outcome so far. In adults surviving long term, bone marrow transplant (BMT) nephropathy is the most frequent renal complication, although a considerable variation in incidence (up to 70%) has been published, partly due to various definitions and manifestations. Little is known about the long-term outcome of renal function in patients treated with HSCT in childhood. However, chronic renal failure has been reported in 0%-28%, but no end-stage renal failure has been published so far. Tubular function following HSCT is rarely investigated, although its impact on long-term survivors of BMT in childhood might be of some importance, especially for growth and bone metabolism.

Ewing tumour: incidence, prognosis and treatment options

Ewing tumours, i.e. Ewing's sarcoma and malignant peripheral neuroectodermal tumours, are the second most common primary malignant tumours of bone in childhood and adolescence, with an annual incidence rate in Caucasians of 3 per 1 million children <15 years of age. Histopathologically small blue round cell tumours, Ewing tumours show a typical chromosomal rearrangement in >95% of cases linking the EWS gene on chromosome 22q12 to a member of the ETS transcription gene family, most commonly to Fli-1 on 11q24. This fusion contributes to the malignant potential of Ewing tumour cells, indeed antisense oligonucleotides may prevent tumour growth in vitro. After open biopsy, and histological and possibly molecular biological confirmation of the diagnosis, treatment consists of several months of multidrug cytostatic therapy and local therapy. Both surgery and radiotherapy may control local disease, but without consequent cytostatic chemotherapy all patients will eventually succumb to distant metastases. With the use of alkylating agents including doxorubicin, cyclophosphamide and/or ifosfamide, and other cytostatic drugs such as actinomycin D (dactinomycin), vincristine and etoposide, long-term survival can be achieved in >50% of patients with localised disease. Patients with clinically detectable metastases at diagnosis, patients not responding to therapy and patients with disease relapse have a significantly poorer prognosis. Maximum supportive care and local therapy managed by an experienced physician are required in all patients, and inclusion of high-risk patients in phase I and II studies is warranted. Hence, treatment of patients with Ewing tumours should be performed in experienced centres only and preferably within controlled clinical trials.

Human kidney tubules detoxify chloroacetaldehyde, a presumed nephrotoxic metabolite of ifosfamide

The nephrotoxic effects of the antineoplastic drug ifosfamide have been attributed to its hepatic metabolite chloroacetaldehyde. The effects of chloroacetaldehyde on isolated human kidney cortex tubules metabolizing lactate (a physiologic substrate in human kidneys) were investigated. At concentrations of > or =0.5 mM, chloroacetaldehyde was toxic to the human kidney tubules, as demonstrated by a dramatic decrease in cellular ATP levels and a large increase in lactate dehydrogenase release; chloroacetaldehyde also stimulated pyruvate accumulation and inhibited lactate removal and glucose synthesis. These effects, which were associated with incomplete disappearance of chloroacetaldehyde and extensive depletion of the cellular CoA, acetyl-CoA, and glutathione contents, were prevented by the addition of thiol-protecting drugs (mesna and amifostine). Human kidney tubules were demonstrated to metabolize chloroacetaldehyde at high rates, presumably via aldehyde dehydrogenase, which is very active in human kidneys. Carbon-13 nuclear magnetic resonance spectroscopy measurements indicated that human kidney tubules converted [2-(13)C]chloroacetaldehyde to [2-(13)C]chloroacetate, the further metabolism of which was very limited. At equimolar concentrations, chloroacetate was much less toxic than chloroacetaldehyde, indicating that chloroacetate synthesis from chloroacetaldehyde by human kidney tubules represents a detoxification mechanism that could play a role in vivo in preventing or limiting the nephrotoxic effects observed during ifosfamide therapy.

Dose-finding and pharmacological study of ifosfamide in combination with paclitaxel and carboplatin in resistant small-cell lung cancer

BACKGROUND

To find the maximum tolerated dose for ifosfamide in combination with paclitaxel and carboplatin in small-cell lung cancer patients (SCLC), who are resistant to cyclophosphamide, doxorubicin and etoposide (CDE).

PATIENTS AND METHODS

Different dose schedules of ifosfamide were combined with fixed doses of paclitaxel 175 mg/m2 and carboplatin AUC 6 mg/ml min. Included were 30 patients, with a median age of 60 years, and median time off prior cytotoxic treatment of 8 weeks. All patients were previously treated with CDE and 11 had received re-induction CDE.

RESULTS

Dose limiting toxicity of our schedule was persistent thrombocytopenia. None of the patients developed neutropenic fever. Non-haematological toxicity was mild, although two treatment-related deaths occurred. Fifty-four percent of patients had a partial response and median survival time was twenty-five weeks.

CONCLUSIONS

The maximum tolerated dose of this combination for patients with resistant SCLC is ifosfamide 2000 mg/m2 in combination with paclitaxel 175 mg/m2 and carboplatin AUC 6 mg/ml min administered on the first day of a 21-day cycle.

Clinical pharmacokinetics and pharmacodynamics of ifosfamide and its metabolites

This review discusses several issues in the clinical pharmacology of the antitumour agent ifosfamide and its metabolites. Ifosfamide is effective in a large number of malignant diseases. Its use, however, can be accompanied by haematological toxicity, neurotoxicity and nephrotoxicity. Since its development in the middle of the 1960s, most of the extensive metabolism of ifosfamide has been elucidated. Identification of specific isoenzymes responsible for ifosfamide metabolism may lead to an improved efficacy/toxicity ratio by modulation of the metabolic pathways. Whether ifosfamide is specifically transported by erythrocytes and which activated ifosfamide metabolites play a key role in this transport is currently being debated. In most clinical pharmacokinetic studies, the phenomenon of autoinduction has been observed, but the mechanism is not completely understood. Assessment of the pharmacokinetics of ifosfamide and metabolites has long been impaired by the lack of reliable bioanalytical assays. The recent development of improved bioanalytical assays has changed this dramatically, allowing extensive pharmacokinetic assessment, identifying key issues such as population differences in pharmacokinetic parameters, differences in elimination dependent upon route and schedule of administration, implications of the chirality of the drug and interpatient pharmacokinetic variability. The mechanisms of action of cytotoxicity, neurotoxicity, urotoxicity and nephrotoxicity have been pivotal issues in the assessment of the pharmacodynamics of ifosfamide. Correlations between the new insights into ifosfamide metabolism, pharmacokinetics and pharmacodynamics will rationalise the further development of therapeutic drug monitoring and dose individualisation of ifosfamide treatment.

Development of ifosfamide-induced nephrotoxicity: prospective follow-up in 75 patients

PURPOSE

This study was performed to describe prospectively the development and prognosis of severe ifosfamide-induced nephrotoxicity and to define the period of recommended renal follow-up after ifosfamide chemotherapy.

PATIENTS AND METHODS

Renal function was followed in 75 patients after cessation of chemotherapy starting within the first year off therapy; median follow-up time was 31 months. The glomerular filtration rate was estimated by using the Schwartz formula. Proximal tubular transport capacities were evaluated for amino acids, phosphate, sodium, and glucose. In addition, serum bicarbonate level and alkaline phosphatase were measured.

RESULTS

Five patients developed renal Fanconi syndrome during follow-up, and another seven patients developed a generalized subclinical tubulopathy. The latter condition always preceded Fanconi syndrome. Severe impairment of amino acid and phosphate reabsorption was seen in 28% and 17.3% of patients, respectively. Reductions in amino acid reabsorption preceded impairment of phosphate reabsorption. In patients with early impairment of phosphate reabsorption, renal prognosis was poor, whereas normal or only mildly impaired amino acid handling virtually excluded progressive tubular damage.

CONCLUSIONS

Ifosfamide-induced renal tubular damage is a potentially progressive disease. Along with measurement of phosphate reabsorption, additional assessment of tubular amino acid handling is suggested, because it allows early discrimination of poor from favorable renal outcomes.