Ifosfamide nephrotoxicity: limited influence of metabolism and mode of administration during repeated therapy in paediatrics

Renal toxicity of ifosfamide in children with cancer: an exploratory study integrating aldehyde dehydrogenase enzymatic activity data and a wide-array urinary metabolomics approach

BACKGROUND

Ifosfamide is a major anti-cancer drug in children with well-known renal toxicity. Understanding the mechanisms underlying this toxicity could help identify children at increased risk of toxicity.

METHODS

The IFOS01 study included children undergoing ifosfamide-based chemotherapy for Ewing sarcoma or rhabdomyosarcoma. A fully evaluation of renal function was performed during and after chemotherapy. Proton nuclear magnetic resonance (NMR) and conventional biochemistry were used to detect early signs of ifosfamide-induced tubulopathy. The enzymatic activity of aldehyde dehydrogenase (ALDH) was measured in the peripheral blood lymphocytes as a marker of ifosfamide-derived chloroacetaldehyde detoxification capacity. Plasma and urine concentrations of ifosfamide and dechloroethylated metabolites were quantified.

RESULTS

The 15 participants received a median total ifosfamide dose of 59 g/m2 (range: 24-102), given over a median of 7 cycles (range: 4-14). All children had acute proximal tubular toxicity during chemotherapy that was reversible post-cycle, seen with both conventional assays and NMR. After a median follow-up of 31 months, 8/13 children presented overall chronic toxicity among which 7 had decreased glomerular filtration rate. ALDH enzymatic activity showed high inter- and intra-individual variations across cycles, though overall activity looked lower in children who subsequently developed chronic nephrotoxicity. Concentrations of ifosfamide and metabolites were similar in all children.

CONCLUSIONS

Acute renal toxicity was frequent during chemotherapy and did not allow identification of children at risk for long-term toxicity. A role of ALDH in late renal dysfunction is possible so further exploration of its enzymatic activity and polymorphism should be encouraged to improve the understanding of ifosfamide-induced nephrotoxicity.

Fractionated ifosfamide, carboplatin, and etoposide with rituximab as a safe and effective treatment for relapsed/refractory diffuse large B cell lymphoma with severe comorbidities

Although treatment outcomes for diffuse large B cell lymphoma (DLBCL) have improved with the introduction of rituximab, approximately half of patients experience relapsed/refractory (r/r) disease. Furthermore, no standard salvage therapy has yet been established to date, while limitations in treatment options exist due to toxicity and restricted tolerability among elderly patients and/or those with comorbidities. The ICE (ifosfamide, cyclophosphamide, and etoposide) regimen is often used as salvage therapy for r/r DLBCL. Several modified ICE regimens not requiring continuous ifosfamide infusion are available, which can be used in outpatient clinics. This study analyzed the efficacy and toxicity of fractionated ICE with rituximab (f-R-ICE) as a salvage regimen among 47 patients with relapsed/refractory DLBCL (median age upon f-R-ICE initiation, 71 years). The whole cohort had an overall (ORR) and complete response rate of 53.1% (n = 25) and 25.5% (n = 12), respectively, and an estimated 1-year overall survival after f-R-ICE initiation of 57%. Comorbidities were evaluated using the Charlson Comorbidity Index (CCI) upon f-R-ICE initiation. Patients with low CCI scores (68%) had a higher ORR than those with high CCI scores (36.4%) upon f-R-ICE initiation (P = 0.042). In contrast, no significant differences in overall survival (OS) were observed between the low and high CCI groups (1-year OS 56.6% vs. 52.2%; median OS 24 vs. 22.8 months) after initiating f-R-ICE. Our results suggest that f-R-ICE is a safe and effective salvage therapy for r/r DLBCL and can be used for older patients and/or those with high CCI scores in outpatient clinics.

Early and late adverse renal effects after potentially nephrotoxic treatment for childhood cancer

BACKGROUND

Improvements in diagnostics and treatment for paediatric malignancies resulted in a major increase in survival. However, childhood cancer survivors (CCS) are at risk of developing adverse effects caused by multimodal treatment for their malignancy. Nephrotoxicity is a known side effect of several treatments, including cisplatin, carboplatin, ifosfamide, radiotherapy and nephrectomy, and can cause glomerular filtration rate (GFR) impairment, proteinuria, tubulopathy, and hypertension. Evidence about the long-term effects of these treatments on renal function remains inconclusive. It is important to know the risk of, and risk factors for, early and late adverse renal effects, so that ultimately treatment and screening protocols can be adjusted. This review is an update of a previously published Cochrane Review.

OBJECTIVES

To evaluate existing evidence on the effects of potentially nephrotoxic treatment modalities on the prevalence of renal dysfunction in survivors treated for childhood cancer with a median or mean survival of at least one year after cessation of treatment, where possible in comparison with the general population or CCS treated without potentially nephrotoxic treatment. In addition, to evaluate evidence on associated risk factors, such as follow-up duration, age at time of diagnosis and treatment combinations, as well as the effect of doses.

SEARCH METHODS

On 31 March 2017 we searched the following electronic databases: CENTRAL, MEDLINE and Embase. In addition, we screened reference lists of relevant studies and we searched the congress proceedings of the International Society of Pediatric Oncology (SIOP) and The American Society of Pediatric Hematology/Oncology (ASPHO) from 2010 to 2016/2017.

SELECTION CRITERIA

Except for case reports, case series and studies including fewer than 20 participants, we included studies with all study designs that reported on renal function (one year or longer after cessation of treatment), in CCS treated before the age of 21 years with cisplatin, carboplatin, ifosfamide, radiation involving the kidney region, a nephrectomy, or a combination of two or more of these treatments. When not all treatment modalities were described or the study group of interest was unclear, a study was not eligible for the evaluation of prevalence. We still included it for the assessment of risk factors if it had performed a multivariable analysis.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction using standardised data collection forms. We performed analyses according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

Apart from the remaining 37 studies included from the original review, the search resulted in the inclusion of 24 new studies. In total, we included 61 studies; 46 for prevalence, six for both prevalence and risk factors, and nine not meeting the inclusion criteria, but assessing risk factors. The 52 studies evaluating the prevalence of renal dysfunction included 13,327 participants of interest, of whom at least 4499 underwent renal function testing. The prevalence of adverse renal effects ranged from 0% to 84%. This variation may be due to diversity of included malignancies, received treatments, reported outcome measures, follow-up duration and the methodological quality of available evidence.Seven out of 52 studies, including 244 participants, reported the prevalence of chronic kidney disease, which ranged from 2.4% to 32%.Of these 52 studies, 36 studied a decreased (estimated) GFR, including at least 432 CCS, and found it was present in 0% to 73.7% of participants. One eligible study reported an increased risk of glomerular dysfunction after concomitant treatment with aminoglycosides and vancomycin in CCS receiving total body irradiation (TBI). Four non-eligible studies assessing a total cohort of CCS, found nephrectomy and (high-dose (HD)) ifosfamide as risk factors for decreased GFR. The majority also reported cisplatin as a risk factor. In addition, two non-eligible studies showed an association of a longer follow-up period with glomerular dysfunction.Twenty-two out of 52 studies, including 851 participants, studied proteinuria, which was present in 3.5% to 84% of participants. Risk factors, analysed by three non-eligible studies, included HD cisplatin, (HD) ifosfamide, TBI, and a combination of nephrectomy and abdominal radiotherapy. However, studies were contradictory and incomparable.Eleven out of 52 studies assessed hypophosphataemia or tubular phosphate reabsorption (TPR), or both. Prevalence ranged between 0% and 36.8% for hypophosphataemia in 287 participants, and from 0% to 62.5% for impaired TPR in 246 participants. One non-eligible study investigated risk factors for hypophosphataemia, but could not find any association.Four out of 52 studies, including 128 CCS, assessed the prevalence of hypomagnesaemia, which ranged between 13.2% and 28.6%. Both non-eligible studies investigating risk factors identified cisplatin as a risk factor. Carboplatin, nephrectomy and follow-up time were other reported risk factors.The prevalence of hypertension ranged from 0% to 50% in 2464 participants (30/52 studies). Risk factors reported by one eligible study were older age at screening and abdominal radiotherapy. A non-eligible study also found long follow-up time as risk factor. Three non-eligible studies showed that a higher body mass index increased the risk of hypertension. Treatment-related risk factors were abdominal radiotherapy and TBI, but studies were inconsistent.Because of the profound heterogeneity of the studies, it was not possible to perform meta-analyses. Risk of bias was present in all studies.

AUTHORS' CONCLUSIONS

The prevalence of adverse renal effects after treatment with cisplatin, carboplatin, ifosfamide, radiation therapy involving the kidney region, nephrectomy, or any combination of these, ranged from 0% to 84% depending on the study population, received treatment combination, reported outcome measure, follow-up duration and methodological quality. With currently available evidence, it was not possible to draw solid conclusions regarding the prevalence of, and treatment-related risk factors for, specific adverse renal effects. Future studies should focus on adequate study designs and reporting, including large prospective cohort studies with adequate control groups when possible. In addition, these studies should deploy multivariable risk factor analyses to correct for possible confounding. Next to research concerning known nephrotoxic therapies, exploring nephrotoxicity after new therapeutic agents is advised for future studies. Until more evidence becomes available, CCS should preferably be enrolled into long-term follow-up programmes to monitor their renal function and blood pressure.

Late renal toxicity of treatment for childhood malignancy: risk factors, long-term outcomes, and surveillance

Chronic glomerular and tubular nephrotoxicity is reported in 20-50% and 20-25%, respectively, of children and adolescents treated with ifosfamide and 60-80% and 10-30%, respectively, of those given cisplatin. Up to 20% of children display evidence of chronic glomerular damage after unilateral nephrectomy for a renal tumour. Overall, childhood cancer survivors have a ninefold higher risk of developing renal failure compared with their siblings. Such chronic nephrotoxicity may have multiple causes, including chemotherapy, radiotherapy exposure to kidneys, renal surgery, supportive care drugs and tumour-related factors. These cause a wide range of chronic glomerular and tubular toxicities, often with potentially severe clinical sequelae. Many risk factors for developing nephrotoxicity, mostly patient and treatment related, have been described, but we remain unable to predict all episodes of renal damage. This implies that other factors may be involved, such as genetic polymorphisms influencing drug metabolism. Although our knowledge of the long-term outcomes of chronic nephrotoxicity is increasing, there is still much to learn, including how we can optimally predict or achieve early detection of nephrotoxicity. Greater understanding of the pathogenesis of nephrotoxicity is needed before its occurrence can be prevented.

Phase I/II Trial of Paclitaxel With Ifosfamide Followed by High-Dose Paclitaxel, Ifosfamide, and Carboplatin (TI-TIC) With Autologous Stem Cell Reinfusion for Salvage Treatment of Germ Cell Tumors

BACKGROUND

Salvage high-dose (HD) chemotherapy with autologous stem cell transplant (ASCT), consisting of 2 to 3 sequential cycles of HD carboplatin and etoposide (CE) can achieve durable remissions in approximately half of patients with relapsed germ cell tumors. To improve on these results and based on success with paclitaxel, ifosfamide, and cisplatin (TIP) as salvage conventional-dose chemotherapy, we conducted a phase I/II trial of HD paclitaxel with ifosfamide (TI), substituting carboplatin for cisplatin to allow dose escalation.

PATIENTS AND METHODS

Treatment consisted of 1 to 2 cycles of TI and granulocyte colony-stimulating factor for stem cell mobilization followed by 3 cycles of HD TI with carboplatin (TIC) with ASCT every 21 to 28 days. Twenty-six patients were enrolled. For phase I, a standard 3+3 dose-escalation design was used.

RESULTS

With no dose-limiting toxicities observed, the maximum tolerated dose (MTD) was not reached and the highest prespecified dose level (paclitaxel 250 mg/m(2), ifosfamide 9990 mg/m(2), carboplatin area under the curve 24) was considered the MTD. In phase II, a Simon 2-stage design was used to estimate the complete response (CR) rate at the MTD. With 7 of 11 phase II patients who achieved a CR, efficacy was demonstrated. However, 3 patients developed delayed chronic kidney disease, resulting in premature trial closure.

CONCLUSION

TI-TIC was active in relapsed germ cell tumors but treatment-emergent chronic renal impairment, possibly from overlapping ifosfamide and carboplatin, preclude its further use. TI-CE, consisting of 2 cycles of TI with 3 cycles of HD CE remains the standard of care HD chemotherapy regimen at Memorial Sloan Kettering Cancer Center.

Early and late renal adverse effects after potentially nephrotoxic treatment for childhood cancer

BACKGROUND

Great improvements in diagnostics and treatment for malignant disease in childhood have led to a major increase in survival. However, childhood cancer survivors (CCS) are at great risk for developing adverse effects caused by multimodal treatment for their malignancy. Nephrotoxicity is one of these known (acute) side effects of several treatments, including cisplatin, carboplatin, ifosfamide, radiotherapy and nephrectomy, and can cause glomerular filtration rate impairment, proteinuria, tubulopathy and hypertension. However, evidence about the long-term effects of these treatments on renal function remains inconclusive. To reduce the number of (long-term) nephrotoxic events in CCS, it is important to know the risk of, and risk factors for, early and late renal adverse effects, so that ultimately treatment and screening protocols can be adjusted.

OBJECTIVES

To evaluate existing evidence on the effects of potentially nephrotoxic treatment modalities on the prevalence of and associated risk factors for renal dysfunction in survivors treated for childhood cancer with a median or mean survival of at least one year after cessation of treatment, where possible in comparison with healthy controls or CCS treated without potentially nephrotoxic treatment.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2011), MEDLINE/PubMed (from 1945 to December 2011) and EMBASE/Ovid (from 1980 to December 2011).

SELECTION CRITERIA

With the exception of case reports, case series and studies including fewer than 20 participants, we included studies with all study designs that reported on renal function (one year or longer after cessation of treatment) in children and adults who were treated for a paediatric malignancy (aged 18 years or younger at diagnosis) with cisplatin, carboplatin, ifosfamide, radiation including the kidney region and/or a nephrectomy.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, risk of bias assessment and data extraction using standardised data collection forms. Analyses were performed according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

The search strategy identified 5504 studies, of which 5138 were excluded on the basis of title and/or abstract. The full-text screening of the remaining 366 articles resulted in the inclusion of 57 studies investigating the prevalence of and sometimes also risk factors for early and late renal adverse effects of treatment for childhood cancer. The 57 studies included at least 13,338 participants of interest for this study, of whom at least 6516 underwent renal function testing. The prevalence of renal adverse effects ranged from 0% to 84%. This variation may be due to diversity in included malignancies, prescribed treatments, reported outcome measurements and the methodological quality of available evidence.Chronic kidney disease/renal insufficiency (as defined by the authors of the original studies) was reported in 10 of 57 studies. The prevalence of chronic kidney disease ranged between 0.5% and 70.4% in the 10 studies and between 0.5% and 18.8% in the six studies that specifically investigated Wilms' tumour survivors treated with a unilateral nephrectomy.A decreased (estimated) glomerular filtration rate was present in 0% to 50% of all assessed survivors (32/57 studies). Total body irradiation; concomitant treatment with aminoglycosides, vancomycin, amphotericin B or cyclosporin A; older age at treatment and longer interval from therapy to follow-up were significant risk factors reported in multivariate analyses. Proteinuria was present in 0% to 84% of all survivors (17/57 studies). No study performed multivariate analysis to assess risk factors for proteinuria.Hypophosphataemia was assessed in seven studies. Reported prevalences ranged between 0% and 47.6%, but four of seven studies found a prevalence of 0%. No studies assessed risk factors for hypophosphataemia using multivariate analysis. The prevalence of impairment of tubular phosphate reabsorption was mostly higher (range 0% to 62.5%; 11/57 studies). Higher cumulative ifosfamide dose, concomitant cisplatin treatment, nephrectomy and longer follow-up duration were significant risk factors for impaired tubular phosphate reabsorption in multivariate analyses.Treatment with cisplatin and carboplatin was associated with a significantly lower serum magnesium level in multivariate analysis, and the prevalence of hypomagnesaemia ranged between 0% and 37.5% in the eight studies investigating serum magnesium.Hypertension was investigated in 24 of the 57 studies. Reported prevalences ranged from 0% to 18.2%. A higher body mass index was the only significant risk factor noted in more than one multivariate analysis. Other reported factors that significantly increased the risk of hypertension were use of total body irradiation, abdominal irradiation, acute kidney injury, unrelated or autologous stem cell donor type, growth hormone therapy and older age at screening. Previous infection with hepatitis C significantly decreased the risk of hypertension.Because of the profound heterogeneity of the studies, it was not possible to perform any meta-analysis.

AUTHORS' CONCLUSIONS

The prevalence of renal adverse events after treatment with cisplatin, carboplatin, ifosfamide, radiation therapy involving the kidney region and/or nephrectomy ranged from 0% to 84%. With currently available evidence, it was not possible to draw any conclusions with regard to prevalence of and risk factors for renal adverse effects. Future studies should focus on adequate study design and reporting and should deploy multivariate risk factor analysis to correct for possible confounding. Until more evidence becomes available, CCS should be enrolled into long-term follow-up programmes to monitor their renal function and blood pressure.

Oxazaphosphorine bioactivation and detoxification The role of xenobiotic receptors

Oxazaphosphorines, with the most representative members including cyclophosphamide, ifosfamide, and trofosfamide, constitute a class of alkylating agents that have a broad spectrum of anticancer activity against many malignant ailments including both solid tumors such as breast cancer and hematological malignancies such as leukemia and lymphoma. Most oxazaphosphorines are prodrugs that require hepatic cytochrome P450 enzymes to generate active alkylating moieties before manifesting their chemotherapeutic effects. Meanwhile, oxazaphosphorines can also be transformed into non-therapeutic byproducts by various drug-metabolizing enzymes. Clinically, oxazaphosphorines are often administered in combination with other chemotherapeutics in adjuvant treatments. As such, the therapeutic efficacy, off-target toxicity, and unintentional drug-drug interactions of oxazaphosphorines have been long-lasting clinical concerns and heightened focuses of scientific literatures. Recent evidence suggests that xenobiotic receptors may play important roles in regulating the metabolism and clearance of oxazaphosphorines. Drugs as modulators of xenobiotic receptors can affect the therapeutic efficacy, cytotoxicity, and pharmacokinetics of coadministered oxazaphosphorines, providing a new molecular mechanism of drug-drug interactions. Here, we review current advances regarding the influence of xenobiotic receptors, particularly, the constitutive androstane receptor, the pregnane X receptor and the aryl hydrocarbon receptor, on the bioactivation and detoxification of oxazaphosphorines, with a focus on cyclophosphamide and ifosfamide.

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.

The role of constitutive androstane receptor in oxazaphosphorine-mediated induction of drug-metabolizing enzymes in human hepatocytes

PURPOSE

To investigate the roles of the constitutive androstane receptor (CAR) in cyclophosphamide (CPA)- and ifosfamide (IFO)-mediated induction of hepatic drug-metabolizing enzymes (DME).

METHODS

Induction of DMEs was evaluated using real-time RT-PCR and Western blotting analysis in human primary hepatocyte (HPH) cultures. Activation of CAR, pregnane X receptor (PXR), and aryl hydrocarbon receptor by CPA and IFO was assessed in cell-based reporter assays in HepG2 cells and/or nuclear translocation assays in HPHs.

RESULTS

CYP2B6 reporter activity was significantly enhanced by CPA and IFO in HepG2 cells co-transfected with CYP2B6 reporter plasmid and a chemical-responsive human CAR variant (CAR1 + A) construct. Real-time RT-PCR and Western blotting analysis in HPHs showed that both CPA and IFO induced the expressions of CYP2B6 and CYP3A4. Notably, treatment of HPHs with CPA but not IFO resulted in significant nuclear accumulation of CAR, which represents the initial step of CAR activation. Further studies in HPHs demonstrated that selective inhibition of PXR by sulforaphane preferentially repressed IFO- over CPA-mediated induction of CYP2B6.

CONCLUSION

These results provide novel insights into the differential roles of CAR in the regulation of CPA- and IFO-induced DME expression and potential drug-drug interactions.

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.

Glomerular toxicity persists 10 years after ifosfamide treatment in childhood and is not predictable by age or dose

BACKGROUND

This prospective longitudinal single institution cohort study evaluated the natural history of and risk factors for chronic nephrotoxicity 10 years after ifosfamide treatment in childhood.

PROCEDURE

Twenty-five patients (16 males) treated with ifosfamide were investigated at end of treatment (End), 1 and 10 years later. Glomerular filtration rate (GFR), serum phosphate (PO4) and bicarbonate (HCO3) and renal tubular threshold for phosphate (Tmp/GFR) were measured, and total nephrotoxicity score (Ns) graded.

RESULTS

More patients had a low GFR at 1 (72%) and 10 (50%) years than at End (26%) (P = 0.006 for End vs. 1 year). Electrolyte supplementation requirements for tubular toxicity resolved by 10 years (0% vs. 32% at End and 24% at 1 year; both P < 0.05). At 10 years, 17% of patients had moderate overall nephrotoxicity and 13% clinically significant reduction of GFR (<60 ml/min/1.73 m2). Neither dose nor age at treatment predicted any measure of toxicity at 10 years or reduced GFR at any timepoint. Higher cumulative ifosfamide dose correlated with greater tubular and overall nephrotoxicity at End and/or 1 year (P < 0.05 for each of PO4, HCO3, Tmp/GFR, Ns), but age at treatment did not differ between patients with normal or abnormal results.

CONCLUSIONS

Although clinically significant tubular toxicity had resolved by 10 years, GFR was <60 ml/min/1.73 m2 in 13% of patients, raising concerns about very long-term glomerular function. Higher cumulative dose was associated with greater tubular and overall toxicity at End and 1 year, but not at 10 years. Age at treatment did not predict nephrotoxicity at any timepoint.

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.

Recurrent, refractory, metastatic and/or unresectable pediatric sarcomas: treatment options for young people ‘off the roadmap’

Although sarcoma surgery is very important for cancer control, it is not always possible or practical to offer in some situations, including sarcoma recurrences, metastatic disease and/or unacceptable loss of function. We review some pragmatic approaches and examples of how to balance indications, risks and alternatives to control cancer in young people with sarcomas that are no longer using ‘front-line’ therapy. Radiotherapy combined with chemotherapy and outpatient ‘continuation’ chemotherapy regimens using drugs that cause less alopecia can improve function and quality of life. Some effective strategies to help cope when cure is not possible may include tumor ablation techniques performed in interventional radiology and percutaneous nerve blocks. Family centered care and effective problem solving of difficult issues can be greatly facilitated by consultation with a multidisciplinary team experienced in the management of very difficult cases. Treatment of young people with recurrent, relapsed and/or metastatic sarcoma still remains an art very much in the realm of compassion not protocol and persistent advocacy is required for the young person for whom cure may not be possible. A reduction of suffering and assistance in writing more chapters of a rich life narrative is the goal.

Variations in schedules of ifosfamide administration: a better understanding of its implications on pharmacokinetics through a randomized cross-over study

PURPOSE

The metabolism of ifosfamide is a delicate balance between a minor activation pathway (4-hydroxylation) and a mainly toxification pathway (N-dechloroethylation), and there remains uncertainty as to the optimal intravenous schedule.

METHODS

This study assesses ifosfamide pharmacokinetics (PK) according to two standard schedules. Using a 1:1 randomized trial design, we prospectively evaluated ifosfamide PK on two consecutive cycles of 3 g/m2/day for 3 days (9 g/m2/cycle) given in one of two schedules either by continuous infusion (CI) or short (3 h) infusion. Highly sensitive analytical methods allowed determination of concentrations of ifosfamide and the key metabolites 4-hydroxy-ifosfamide, 2- and 3-dechloroethyl-ifosfamide.

RESULTS

Extensive PK analysis was available in 12 patients and showed equivalence between both schedules (3 h versus CI) based on area under the curves (micromol/l x h) for ifosfamide, 4-hydroxy-ifosfamide, 2- and 3-dechloroethyl-ifosfamide (9,379 +/- 2,638 versus 8,307 +/- 1,995, 152 +/- 59 versus 161 +/- 77, 1,441 +/- 405 versus 1,388 +/- 393, and 2,808 +/- 508 versus 2,634 +/- 508, respectively, all P > 0.2). The classical auto-induction of metabolism over the 3 days of infusion was confirmed for both schedules.

CONCLUSION

This study confirms similar PK for both active and toxic metabolites of ifosfamide in adult cancer patients when 9 g/m2 of ifosfamide is administered over 3 days by CI or daily 3-h infusions.

Metabolism and transport of oxazaphosphorines and the clinical implications

The oxazaphosphorines including cyclophosphamide (CPA), ifosfamide (IFO), and trofosfamide represent an important group of therapeutic agents due to their substantial antitumor and immuno-modulating activity. CPA is widely used as an anticancer drug, an immunosuppressant, and for the mobilization of hematopoetic progenitor cells from the bone marrow into peripheral blood prior to bone marrow transplantation for aplastic anemia, leukemia, and other malignancies. New oxazaphosphorines derivatives have been developed in an attempt to improve selectivity and response with reduced toxicity. These derivatives include mafosfamide (NSC 345842), glufosfamide (D19575, beta-D-glucosylisophosphoramide mustard), NSC 612567 (aldophosphamide perhydrothiazine), and NSC 613060 (aldophosphamide thiazolidine). This review highlights the metabolism and transport of these oxazaphosphorines (mainly CPA and IFO, as these two oxazaphosphorine drugs are the most widely used alkylating agents) and the clinical implications. Both CPA and IFO are prodrugs that require activation by hepatic cytochrome P450 (CYP)-catalyzed 4-hydroxylation, yielding cytotoxic nitrogen mustards capable of reacting with DNA molecules to form crosslinks and lead to cell apoptosis and/or necrosis. Such prodrug activation can be enhanced within tumor cells by the CYP-based gene directed-enzyme prodrug therapy (GDEPT) approach. However, those newly synthesized oxazaphosphorine derivatives such as glufosfamide, NSC 612567 and NSC 613060, do not need hepatic activation. They are activated through other enzymatic and/or non-enzymatic pathways. For example, both NSC 612567 and NSC 613060 can be activated by plain phosphodiesterase (PDEs) in plasma and other tissues or by the high-affinity nuclear 3'-5' exonucleases associated with DNA polymerases, such as DNA polymerases and epsilon. The alternative CYP-catalyzed inactivation pathway by N-dechloroethylation generates the neurotoxic and nephrotoxic byproduct chloroacetaldehyde (CAA). Various aldehyde dehydrogenases (ALDHs) and glutathione S-transferases (GSTs) are involved in the detoxification of oxazaphosphorine metabolites. The metabolism of oxazaphosphorines is auto-inducible, with the activation of the orphan nuclear receptor pregnane X receptor (PXR) being the major mechanism. Oxazaphosphorine metabolism is affected by a number of factors associated with the drugs (e.g., dosage, route of administration, chirality, and drug combination) and patients (e.g., age, gender, renal and hepatic function). Several drug transporters, such as breast cancer resistance protein (BCRP), multidrug resistance associated proteins (MRP1, MRP2, and MRP4) are involved in the active uptake and efflux of parental oxazaphosphorines, their cytotoxic mustards and conjugates in hepatocytes and tumor cells. Oxazaphosphorine metabolism and transport have a major impact on pharmacokinetic variability, pharmacokinetic-pharmacodynamic relationship, toxicity, resistance, and drug interactions since the drug-metabolizing enzymes and drug transporters involved are key determinants of the pharmacokinetics and pharmacodynamics of oxazaphosphorines. A better understanding of the factors that affect the metabolism and transport of oxazaphosphorines is important for their optional use in cancer chemotherapy.

Pharmacokinetics and metabolism of ifosfamide in relation to DNA damage assessed by the COMET assay in children with cancer

The degree of damage to DNA following ifosfamide (IFO) treatment may be linked to the therapeutic efficacy. The pharmacokinetics and metabolism of IFO were studied in 19 paediatric patients, mostly with rhabdomyosarcoma or Ewings sarcoma. Ifosfamide was dosed either as a continuous infusion or as fractionated doses over 2 or 3 days. Samples of peripheral blood lymphocytes were obtained during and up to 96 h after treatment, and again prior to the next cycle of chemotherapy. DNA damage was measured using the alkaline COMET assay, and quantified as the percentage of highly damaged cells per sample. Samples were also taken for the determination of IFO and metabolites. Pharmacokinetics and metabolism of IFO were comparable with previous studies. Elevations in DNA damage could be determined in all patients after IFO administration. The degree of damage increased to a peak at 72 h, but had returned to pretreatment values prior to the next dose of chemotherapy. There was a good correlation between area under the curve of IFO and the cumulative percentage of cells with DNA damage (r²=0.554, P=0.004), but only in those patients receiving fractionated dosing. The latter patients had more DNA damage (mean±s.d., 2736±597) than those patients in whom IFO was administered by continuous infusion (1453±730). The COMET assay can be used to quantify DNA damage following IFO therapy. Fractionated dosing causes a greater degree of DNA damage, which may suggest a greater degree of efficacy, with a good correlation between pharmacokinetic and pharmacodynamic data.

A tubule cell model for ifosfamide nephrotoxicity

Mechanisms leading to ifosfamide (IF)-induced renal damage have not been fully elucidated. Recent work suggests that localized renal tubular metabolism of IF and the production of the nephrotoxic chloroacetaldehyde may lead to nephrotoxicity. Presently no pharmacological method to reduce IF nephrotoxicity has been identified. The objectives of this study were to establish a tubule cell model for IF nephrotoxicity, to verify whether renal proximal tubular cells have the necessary cytochrome P450 (CYP) enzymes to oxidize IF, and whether they can metabolize IF to chloroacetaldehyde. CYP3A, and 2B mRNA and protein were identified in LLCPK-1 cells. The cells metabolized the R- and S-IF enantiomers to their respective 2- and 3-dechloroethylifosfamide metabolites, by-products of chloroacetal dehyde formation. Metabolite production was both time and concentration-dependent. IF did not affect cell viability. In contrast, glutathione-depleted cells showed time and dose-dependent damage. The presence of the relevant CYP enzymes in renal tubular cells along with their ability to metabolize IF to its 2- and 3-dechloroethylifosfamide metabolites suggests that nephrotoxic damage may result from the localized production of chloroacetaldehyde. Glutathione is a major defence mechanism against IF toxicity, thus pharmacological methods for replenishing intracellular glutathione may be effective in modulating IF-induced nephrotoxicity. Key words: LLCPK-1, metabolism, ifosfamide, renal, CYP3A, CYP2B.

Pharmacokinetic studies in children with cancer

We reviewed the current status of our knowledge of pharmacokinetics and pharmacodynamics of some anti-neoplastic drugs, used in the treatment of childhood cancer. Extrapolation of data from pharmacokinetic studies in adults to the paediatric population is often not feasible. Specific studies in children are needed. Of all reviewed anti-neoplastic drugs methotrexate appears to be most extensively studied. Methotrexate pharmacokinetics is correlated with toxicity and response to therapy, and it has been shown that individualized adaptive dosing of methotrexate is correlated with a better response to therapy without increasing toxicity in children with ALL and osteosarcoma. Of most of the other reviewed anti-neoplastic drugs it is demonstrated that pharmacokinetics is correlated with toxicity, and of some drugs a relationship of pharmacokinetics with response to therapy is demonstrated as well. In case of cytarabine, etoposide, and teniposide, individualized dosing also appears to be feasible. However, there is no evidence that this strategy improves response to therapy. Specifically data on pharmacokinetic and pharmacodynamic correlations and effect of pharmacokinetically guided, individualized dosing are important for the design of optimal cancer chemotherapy for individual patients. Unfortunately for a considerable number of anti-neoplastic drugs these specific data are lacking in children and future research is needed.

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.

Quantitative assessment of the clavicle radiostructure as a tool for estimation of the osteopathic effect of breast cancer chemotherapy

Radiological structure (trabeculation) of the clavicle was quantitatively evaluated using the chest X-ray images obtained in 36 pre-menopausal women subjected to CMF (cyclophosphamide, methotrexate, fluorouracil) chemotherapy. For comparison, the values of the quantitative radiostructural indices were estimated from the X-ray images obtained in 65 age-matched pre-menopausal healthy women and 19 post-menopausal women with clinically confirmed osteoporosis. For the analyses, the high-quality routine chest P-A films were used in which the central segment of the clavicle was well visualised. Evaluation of the skeletal radiostructure was carried out using the original software developed by K.W. Zieliński which, in addition to standardising the quality of the image, calculated the structural density as well as the arrangement and mean thickness of the trabeculae. The results demonstrate in a reproducible way that structural density and mean thickness of the clavicular trabeculae were significantly (p < 0.01) lower in pre-menopausal, CMF-treated and post-menopausal, osteoporotic patients than in healthy, control women. Likewise, the relative radiological density of the clavicle was reduced in the former two groups of women as compared to their control counterparts and the difference approached statistical significance. When the X-ray films were compared in each breast cancer patient before and after the chemotherapy the values of all the three parameters were decreased in up to 86% of the treated patients. Overall, the obtained results demonstrate the significant osteopathic side effect of the CMF chemotherapy in pre-menopausal breast cancer patients.

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.

Risk factors for nephrotoxicity after ifosfamide treatment in children: a UKCCSG Late Effects Group study. United Kingdom Children's Cancer Study Group

The aim of this multicentre study was to document the nephrotoxicity associated with ifosfamide and evaluate risk factors in 148 children and young people with sarcomas who underwent investigation of renal function on one occasion each, at a median of 6 (range 1-47) months after completion of ifosfamide (median dose 62.0 (range 6.1-165.0) g/m2). Investigations included glomerular filtration rate (GFR), serum bicarbonate (HCO3) and phosphate (PO4), and renal tubular threshold for phosphate (Tmp/GFR). A clinically relevant nephrotoxicity score' was derived. GFR was < 90 ml/min/1.73 m2 in 61 of 123 evaluable patients, Tmp/GFR < 0.9-1.1 mmol/l (age-dependent) in 45/103, serum PO4 < 0.9-1.mmol/l (age-dependent) in 28/135, and serum HCO3 < 20 (< 18 in infants) mmol/l in 22/95. Of 76 fully evaluable patients: 50% had mild, 20% moderate and 8% severe nephrotoxicity. Higher total ifosfamide dose correlated significantly with greater glomerular and tubular toxicity (P < 0.01); other risk factors, including age at treatment, demonstrated no consistent significant independent effect. Chronic ifosfamide-related glomerular and proximal tubular toxicity were common in this large comprehensive study. Restriction of total ifosfamide dose to < 84 g/m2 will reduce the frequency of, but not abolish, clinically significant nephrotoxicity, whilst doses > 119 g/m2 are associated with a very high risk of severe toxicity.

Metabolism and pharmacokinetics of oxazaphosphorines

The 2 most commonly used oxazaphosphorines are cyclophosphamide and ifosfamide, although other bifunctional mustard analogues continue to be investigated. The pharmacology of these agents is determined by their metabolism, since the parent drug is relatively inactive. For cyclophosphamide, elimination of the parent compound is by activation to the 4-hydroxy metabolite, although other minor pathways of inactivation also play a role. Ifosfamide is inactivated to a greater degree by dechloroethylation reactions. More robust assay methods for the 4-hydroxy metabolites may reveal more about the clinical pharmacology of these drugs, but at present the best pharmacodynamic data indicate an inverse relationship between plasma concentration of parent drug and either toxicity or antitumour effect. The metabolism of cyclophosphamide is of particular relevance in the application of high dose chemotherapy. The activation pathway of metabolism is saturable, such that at higher doses (greater than 2 to 4 g/m2) a greater proportion of the drug is eliminated as inactive metabolites. However, both cyclophosphamide and ifosfamide also act to induce their own metabolism. Since most high dose regimens require a continuous infusion or divided doses over several days, saturation of metabolism may be compensated for, in part, by auto-induction. Although a quantitative distinction may be made between the cytochrome P450 isoforms responsible for the activating 4-hydroxylation reaction and those which mediate the dechloroethylation reactions, selective induction of the activation pathway, or inhibition of the inactivating pathway, has not been demonstrated clinically. Mathematical models to describe and predict the relative contributions of saturation and autoinduction to the net activation of cyclophosphamide have been developed. However, these require careful validation and may not be applicable outside the exact regimen in which they were derived. A further complication is the chiral nature of these 2 drugs, with some suggestion that one enantiomer may have a favourable profile of metabolism over the other. That the oxazaphosphorines continue to be the subject of intensive investigation over 30 years after their introduction into clinical practice is partly because of their antitumour activity. Further advances in analytical and molecular pharmacological techniques may further optimise their use and allow rational design of more selective analogues.

High-performance liquid chromatographic-fluorescent method to determine chloroacetaldehyde, a neurotoxic metabolite of the anticancer drug ifosfamide, in plasma and in liver microsomal incubations

Chloroacetaldehyde (CA) is a nephrotoxic and neurotoxic metabolite of the anticancer drug ifosfamide (IFA) and is a dose-limiting factor in IFA-based chemotherapy. Plasma levels of CA in IFA-treated cancer patients are often difficult to determine due to the lack of a sufficiently sensitive and specific analytical method. We have developed a simple and sensitive HPLC method with fluorescence detection to measure CA formation catalyzed by liver cytochrome P450 enzymes, either in vivo in IFA-injected rats or in vitro in liver microsomal incubations. This method is based on the formation of the highly fluorescent adduct 1-N(6)-ethenoadenosine from the reaction of CA with adenosine (10 mM) at pH 4.5 upon heating at 80 degrees C for 2 h. The derivatization mixture is directly injected onto a C18 HPLC column and is monitored with a fluorescence detector. Calibration curves are linear (r > 0.999) over a wide range of CA concentrations (5-400 pmol). The limit of detection of CA in plasma using this method is <0.1 microM and only 50 microl of plasma is required for the assay. By coupling this method with a recently described HPLC-fluorescent method to determine acrolein, a cytochrome P450 metabolite of IFA formed during the activation of the drug by 4-hydroxylation, the two major, alternative P450-catalyzed pathways of IFA metabolism can be monitored from the same plasma samples or liver microsomal incubations and the partitioning of drug between these two pathways thereby quantitated. This assay may prove to be useful for studies of IFA metabolism aimed at identifying factors that contribute to individual differences in CA formation and in developing approaches to minimize CA formation while maximizing IFA cytotoxicity.

The influence of ifosfamide scheduling on acute nephrotoxicity in children

Nephrotoxicity is a significant problem in children after treatment with ifosfamide. Acute changes in renal function were compared in 16 children receiving 9 g m(-2) of ifosfamide as a 72-h continuous infusion on one occasion and, on another course, divided into three 1-h infusions on consecutive days. Subclinical acute nephrotoxicity was demonstrated with both schedules, but there were no significant differences in severity.