Pharmacokinetically guided dosing of carboplatin and etoposide during peritoneal dialysis and haemodialysis

Cancer Drug Dosing in Chronic Kidney Disease and Dialysis

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

Chemotherapy for non-Hodgkin lymphoma in the hemodialysis patient: A comprehensive review

Chemotherapy for non-Hodgkin lymphoma (NHL) in the hemodialysis (HD) patient is a challenging situation. Because many drugs are predominantly eliminated by the kidneys, chemotherapy in the HD patient requires special considerations concerning dose adjustments to avoid overdose and toxicities. Conversely, some drugs are removed by HD and may expose the patient to undertreatment, therefore the timing of drug administration in relation to HD sessions must be carefully planned. Also, the metabolites of some drugs show different toxicities and dialysability as compared with the parent drug, therefore this must also be catered for. However, the pharmacokinetics of many chemotherapeutics and their metabolites in HD patients are unknown, and the fact that NHL patients are often treated with distinct multiagent chemotherapy regimens makes the situation more complicated. In a realm where uncertainty prevails, case reports and case series reporting on actual treatment and outcomes are extremely valuable and can aid physicians in decision making from drug selection to dosing. We carried out an exhaustive review of the literature and adopted 48 manuscripts consisting of 66 HD patients undergoing 71 chemotherapy regimens for NHL, summarized the data, and provide recommendations concerning dose adjustments and timing of administration for individual chemotherapeutics where possible. The chemotherapy regimens studied in this review include, but are not limited to, rituximab, cyclophosphamide + vincristine + prednisolone (CVP) and cyclophosphamide + doxorubicin + vincristine + prednisolone (CHOP)-like regimens, chlorambucil, ibrutinib, bendamustine, methotrexate, platinum compounds, cytarabine, gemcitabine, etoposide, ifosfamide, melphalan, busulfan, fludarabine, mogamulizumab, brentuximab vedotin, and 90 Y-ibritumomab tiuxetan.

Cisplatin and carboplatin pharmacokinetics in a pediatric patient with hepatoblastoma receiving peritoneal dialysis

Purpose

Cisplatin and carboplatin are frequently used drugs in the treatment of pediatric hepatoblastoma. Dosing guidelines for these drugs in children requiring peritoneal dialysis are lacking. Here, we describe the case of a 3-year-old boy with pre-existing end-stage renal disease on peritoneal dialysis, requiring treatment with cisplatin and carboplatin for hepatoblastoma.

Methods

Pharmacokinetic data were generated to support clinical dosing decisions, with the aim of adequate exposure and minimal toxicity. In the first chemotherapy cycle, 25% of the standard cisplatin dose and 75% of the carboplatin dose, calculated using the pediatric Calvert formula, were administered. Free platinum concentrations were determined in plasma ultrafiltrate and dialysate samples drawn after administration of cis- and carboplatin.

Results

Cisplatin was well tolerated and the observed AUC of cisplatin were 15.3 and 14.3 mg/L h in cycles 1 and 3, respectively. The calculated AUC of carboplatin in cycle 1 (9.8 mg/mL min) exceeded target AUC of 6.5 mg/mL min and toxicity was observed; therefore, the dose was reduced in cycles 2 and 3. The observed AUC in cycles 2 and 3 was 5.4 and 5.7 mg/mL min respectively. Platinum concentrations in the dialysate showed that 3–4% of the total dose of cisplatin and 10–12% of the total dose of carboplatin were excreted via peritoneal dialysis. Chemotherapy enabled extended hemihepatectomy and complete remission was achieved.

Conclusion

This report shows that it is feasible to measure AUCs for both drugs and to individualize the dose of these drugs according to the PK results and clinical parameters. Our advice for future cases would be to calculate the starting dose of carboplatin using the (pediatric) Calvert formula, assuming a dialytic clearance of zero, and to adjust the dose if required, based on therapeutic drug monitoring.

Over a decade of experience with carboplatin therapeutic drug monitoring in a childhood cancer setting in the United Kingdom

The widely used platinum agent carboplatin represents a good example of an anticancer drug where clear relationships between pharmacological exposure and clinical response and toxicity have previously been shown. Within the setting of childhood cancer, there are defined groups of patients who present a particular challenge when dosing with carboplatin, including neonates and infants, those who are anephric, and poor prognosis patients receiving high-dose chemotherapy. For these groups, nonstandard chemotherapy dosing regimens are currently utilised, often with different approaches between clinical study protocols and between treatment centres. For the treatment of these patient populations in the UK, there is now significant experience in carrying out therapeutic drug monitoring, aiming to consistently achieve target drug exposures, maximise drug efficacy and minimise treatment-related side effects. An ongoing clinical trial is currently providing information on drug exposure for a wide range of anticancer agents in these hard to treat patient populations. In addition to supporting dosing decisions for individual patients, the collection and analysis of these data may allow the development of future dosing regimens. For example, current reduced dosing approaches for neonates and infants based on age or body weight, may well be better replaced by regimens based on a sound pharmacological rationale. The successful use of adaptive carboplatin dosing in childhood cancer should encourage the development of therapeutic drug monitoring approaches more widely in an oncology setting.

Anti-neoplastic agents for patients on peritoneal dialysis: A systematic review

BACKGROUND

There is no clear consensus on the administration of anti-neoplastic agents to patients on peritoneal dialysis. Dose adjustments to prevent serious adverse events are still not established. Thus, the aim of this study was to systematically review current evidence on the use of systemic oncology therapies in peritoneal dialysis.

METHODS

A systematic review was conducted using PubMed, Scopus, and Cochrane. All relevant data was collected, including clinical and pharmacokinetic parameters, with comparison to subjects with normal renal function.

RESULTS

Sixteen studies were included. All were case reports. Eighteen types of anti-cancer drugs were reviewed. Multiple adverse events and altered pharmacokinetics were reported.

CONCLUSION

Data concerning the use of anti-neoplastic drugs in patients on peritoneal dialysis are still sparse. The elimination of anti-cancer agents seems often altered in such patients, resulting in serious adverse events. Based on the available evidence, we suggest the need for dose adjustment of each drug.

Salvage Chemotherapy Followed by Autologous Stem-Cell Transplantation Using Targeted Busulfan for Refractory Diffuse Large B-Cell Lymphoma With Dialysis-Dependent End-Stage Renal Disease

BACKGROUND

A treatment strategy is needed for hemodialysis-dependent patients with end-stage renal disease who have relapsed/refractory diffuse large B-cell lymphoma (DLBCL). We examined the feasibility of salvage chemotherapy followed by autologous stem-cell transplantation (ASCT) and busulfan as a conditioning regimen.

PATIENTS AND METHODS

We provided a patient with refractory DLBCL who was receiving hemodialysis with modified salvage chemotherapies that were based on the mechanism of drug pharmacokinetics and an evaluation of the pharmacokinetics of busulfan. After chemotherapy, the patient underwent ASCT.

RESULTS

The regimen was successfully administered without adverse events.

CONCLUSION

Chemotherapy followed by ASCT using a conditioning regimen of reduced melphalan and pharmacokinetically targeted busulfan is a promising strategy for treating patients with relapsed or refractory DLBCL who also have end-stage renal disease and are receiving hemodialysis.

Extension of the Calvert formula to patients with severe renal insufficiency

PURPOSE

The Calvert formula was derived from the study among patients with glomerular filtration rates (GFRs) of 33-135 ml/min, and it remains unclear whether the formula can be used to calculate optimal and safe dosages of carboplatin in patients with severe renal insufficiency. We evaluated the utility of this formula in patients with severe renal insufficiency.

METHODS

For pharmacokinetic analysis, we studied nine adult Japanese patients with advanced cancer who had an estimated GFR of lower than 30 ml/min/1.73 m(2), as calculated by the Japanese equation for estimating GFR, or who were receiving hemodialysis. The dose of carboplatin was calculated with the Calvert formula, in which GFR was measured by inulin clearance or was assumed to be 0 in patients requiring hemodialysis. Hemodialysis was started 23 h after the end of carboplatin infusion.

RESULTS

Although there was a significant correlation between the estimated and measured carboplatin clearance, the estimated clearance was consistently higher than the measured clearance [mean prediction error ± standard deviation = 41.0 ± 26.3 %] in all seven patients with renal insufficiency (GFR, median 21.4, range 7.8-31.4 ml/min) and in the two hemodialysis patients. Actual areas under the concentration-time curve (AUC) (mg/ml min) were 5.4, 5.7, 6.2, and 9.0 for the four patients with a target AUC (mg/ml min) of 5; 5.7, 6.2, and 7.1 for the three patients with a target AUC (mg/ml min) of 4; and 5.1 and 8.7 for the two hemodialysis patients with a target AUC (mg/ml min) of 5. The measured clearance of carboplatin ranged from 23.0 to 51.3 ml/min in the seven patients not receiving hemodialysis. The pre-hemodialysis carboplatin clearance in the hemodialysis patients was 20.5 and 11.1 ml/min, respectively.

CONCLUSION

For adult patients with severe renal insufficiency, the Calvert formula causes carboplatin overdosing by overestimating the carboplatin clearance.

Pharmacokinetics of Carboplatin in a One-Year-Old Anuric Boy Undergoing Hemodialysis and a Review of the Literature

There have been few reports of carboplatin-based chemotherapy for anuric infants. As we had a chance to treat a one-year-old anuric hepatoblastoma patient with carboplatin, we performed a pharmacokinetic analysis and examined the optimal treatment strategy. A one-year-old anuric boy under peritoneal dialysis was diagnosed with hepatoblastoma. Surgical resection was performed, and administration of carboplatin was scheduled postoperatively aiming at 5 mg·min/mL of the area under the curve from the time of dosing to the time of the last observation (AUC(0-t)). We set the initial dose at 50 mg, higher than that calculated by the Calvert formula (34 mg); the time from the end of carboplatin infusion to the initiation of hemodialysis at 2 h; and the hemodialysis duration at 24 h. The actual AUC0-t was 3.05 mg·min/mL because the elimination half-lives before and during hemodialysis were shorter than expected. The AUC(0-t) after the second dose (100 mg) and the third dose (80 mg) were 7.00 and 4.68 mg·min/mL, respectively. The Calvert formula is not suitable for hemodialysis patients because removal of platinum by hemodialysis is not taken into account. It appears that extrarenal clearance in anuric infants is different from that in adults. We obtained an optimal AUC(0-t) using a dose of 80 mg (200 mg/m(2)), setting the time from the end of carboplatin infusion to the initiation of hemodialysis at 2 h, and performing 8-h hemodialysis. Further accumulation of the pharmacokinetic data of carboplatin is necessary for anuric children.

Carboplatin pharmacokinetics in a patient receiving hemodialysis

With refinements and advances in hemodialysis techniques, survival for patients with end-stage renal disease has improved significantly. To our knowledge, however, no prospective trials have been performed in patients receiving hemodialysis who are also diagnosed with cancer and are candidates for chemotherapy. We describe a 73-year-old man who was diagnosed with high-grade neuroendocrine carcinoma, metastatic to the bone and lymph nodes, and was undergoing hemodialysis. Although cisplatin is more commonly used in the treatment of metastatic neuroendocrine cancers, it may not be the best option in patients who suffer from renal insufficiency. Carboplatin is a second-generation, nonnephrotoxic platinum analog that can be hemodialyzed, although no formal guidelines are available regarding the dosing for patients receiving hemodialysis. This case describes a patient who was treated with five cycles of combination carboplatin 115 mg/m(2) on day 1 and etoposide 50 mg/m(2) on day 1 and day 3 of a 28-day cycle. Dialysis was performed for 3.5 hours starting 90 minutes after completion of carboplatin on day 1. Pharmacokinetic assessments were performed at 1, 2, 4, and 12 hours after chemotherapy infusion on day 1 of cycle 1. Total carboplatin concentrations in plasma and platinum ultrafiltrate were measured. The plasma concentration of free platinum at the end of the infusion was 31,000 ng/ml, and the area under the plasma concentration-time curve was 2.9 minute·mg/ml. No significant carboplatin-related toxicities were reported. This case report indicates that carboplatin can be safely administered in patients receiving hemodialysis.

Model-based drug development applied to oncology

Model-based drug development (MBDD) is an approach that is used to organize the vast and complex data streams that feed the drug development pipelines of small molecule and biotechnology sponsors. Such data streams are ultimately reviewed by the global regulatory community as evidence of a drug's potential to treat and/or harm patients. Some of this information is captured in the scientific literature and prescribing compendiums forming the basis of how new and existing agents will ultimately be administered and further evaluated in the broader patient community. As this data stream evolves, the details of data qualification, the assumptions and/or critical decisions based on these data are lost under conventional drug development paradigms. MBDD relies on the construction of quantitative relationships to connect data from discrete experiments conducted along the drug development pathway. These relationships are then used to ask questions relevant at critical development stages, hopefully, with the understanding that the various scenarios explored represent a path to optimal decision making. Oncology, as a therapeutic area, presents a unique set of challenges and perhaps a different development paradigm as opposed to other disease targets. The poor attrition of development compounds in the recent past attests to these difficulties and provides an incentive for a different approach. In addition, given the reliance on multimodal therapy, oncological disease targets are often treated with both new and older agents spanning several drug classes. As MBDD becomes more integrated into the pharmaceutical research community, a more rational explanation for decisions regarding the development of new oncology agents as well as the proposed treatment regimens that incorporate both new and existing agents can be expected. Hopefully, the end result is a more focussed clinical development programme, which ultimately provides a means to optimize individual patient care.

Successful chemotherapy for small-cell lung cancer in an elderly patient undergoing continuous ambulatory peritoneal dialysis

A standard treatment has not yet been established for elderly small-cell lung cancer patients, especially when they have end-stage renal disease. We report the first case of successful chemoradiotherapy in an elderly small-cell lung cancer patient undergoing continuous ambulatory peritoneal dialysis. A 77-year-old Japanese man on continuous ambulatory peritoneal dialysis was diagnosed as having limited disease small-cell lung cancer. He received four monthly cycles of chemotherapy consisting of carboplatin at 240 mg/m(2) on day 1 and etoposide at 40 mg/m(2) on days 1 and 3. He underwent additional hemodialysis on days 1 and 3, while continuous ambulatory peritoneal dialysis continued as usual on the other days. Following chemotherapy, he underwent hyperfractionated radiotherapy to a total dose of 45 Grey, resulting in complete remission of the disease. A pharmacokinetic study showed an area under the concentration-time curve of carboplatin of 3.41 to 4.88 mg.min/mL, increasing gradually over the first three cycles, while etoposide did not show this gradual increase. The increased area under the concentration-time curve of carboplatin may have reflected a worsened renal function during chemotherapy. Despite dose reductions and favorable areas under the concentration-ime curve of carboplatin, the patient suffered grade 3-4 hematological toxicities, necessitating transfusions and a further dose reduction. The patient died of recurrent small-cell lung cancer 19 months after diagnosis.

Renal failure does not preclude cure in children receiving chemotherapy for Wilms tumor: a report from the National Wilms Tumor Study Group

BACKGROUND

Children with Wilms tumor can develop renal failure during treatment. Since there are few published data concerning the appropriate chemotherapy for this situation, we reviewed the experience of children who developed renal failure while being treated on National Wilms Tumor Study Group (NWTSG) studies 1-4 (1969-1994).

PATIENTS AND METHODS

Data files in the NWTSG Data Center for all patients with Wilms tumor were screened. Patient demographics and tumor and treatment data were abstracted from those who developed renal failure.

RESULTS

Twenty-eight of 5,910 (0.47%) children with Wilms tumor registered on NWTSG studies I through IV (1971-1994) were treated with chemotherapy after developing renal failure. Among these patients vincristine at full dose (0.05 mg/kg dose) did not increase the risk of severe toxicity. Dactinomycin (full dose: 15 mcg/kg day x 5) increased the risk for severe neutropenia when given at 75-100% of full dose. There was no compelling evidence for increased toxicity of doxorubicin when given at 100% versus 50% dosing (full dose: 20 mg/m(2) day x 3), but the number of patients analyzed was small. The overall survival percentage was 39%, but 64% for those patients who were in their initial treatment phase at the time of renal failure.

CONCLUSION

The data suggest that, in the setting of renal failure, reduction of dosing is not necessary for the three main agents used for treatment of newly diagnosed Wilms tumor, and cure is not precluded. Accurate pharmacologic and pharmacokinetic studies are needed for any patient being treated while in renal failure.

Continuous ambulatory peritoneal dialysis: pharmacokinetics and clinical outcome of paclitaxel and carboplatin treatment

Purpose

Administration of chemotherapy in patients with renal failure, treated with hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) is still a challenge and literature data is scarce. Here we present a case study of a patient on CAPD, treated with weekly and three-weekly paclitaxel/carboplatin for recurrent ovarian cancer.

Experimental

During the first, second and ninth cycle of treatment, blood, urine and CAPD samples were collected for pharmacokinetic analysis of paclitaxel and total and unbound carboplatin-derived platinum.

Results

Treatment was well tolerated by the patient. No excessive toxicity was observed and at the end of treatment she was in a complete remission. The plasma pharmacokinetics of paclitaxel were unaltered compared to historical data, with neglectable urinary and CAPD clearance. In contrast, the pharmacokinetics of carboplatin were altered, with doubled half-lives compared to patients with normal renal function. Of the administered carboplatin dose, up to 20% was cleared via the dialysate, while only up to 8% was cleared via the urine.

Conclusion

Paclitaxel and carboplatin can be safely administered to patients with chronic renal failure on CAPD. For paclitaxel the generally applied dose can be administered, and although for carboplatin dose-adjustment is required due to the diminished renal function, the dose can be calculated using Calvert’s formula.

International Society of Geriatric Oncology (SIOG) recommendations for the adjustment of dosing in elderly cancer patients with renal insufficiency

A SIOG taskforce was formed to discuss best clinical practice for elderly cancer patients with renal insufficiency. This manuscript outlines recommended dosing adjustments for cancer drugs in this population according to renal function. Dosing adjustments have been made for drugs in current use which have recommendations in renal insufficiency and the elderly, focusing on drugs which are renally eliminated or are known to be nephrotoxic. Recommendations are based on pharmacokinetic and/or pharmacodynamic data where available. The taskforce recommend that before initiating therapy, some form of geriatric assessment should be conducted that includes evaluation of comorbidities and polypharmacy, hydration status and renal function (using available formulae). Within each drug class, it is sensible to use agents which are less likely to be influenced by renal clearance. Pharmacokinetic and pharmacodynamic data of anticancer agents in the elderly are needed in order to maximise efficacy whilst avoiding unacceptable toxicity.

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.

Effect of haemodialysis on the pharmacokinetics of antineoplastic drugs

Since renal failure itself creates an immunocompromised situation, malignant tumours in haemodialysis patients are increasing due to the prolonged lifespan of these patients. In treating these patients with anticancer agents, dosage reduction is often recommended to avoid adverse drug reactions, particularly for drugs with extensive renal excretion. On the other hand, if an anticancer drug is removed significantly by haemodialysis, dosage increase would be required to ensure adequate therapeutic efficacy. We address in this review the clinical pharmacokinetic aspects of antineoplastic therapy, and the application of pharmacokinetic principles to the adjustment of dosage of anticancer agents in haemodialysis patients.

Pharmacokinetically guided dosing of carboplatin in paediatric cancer patients with bilateral nephrectomy

An approach to carboplatin dosing in children with bilateral nephrectomy using a renal function-based dosing formula with a glomerular filtration rate of zero was investigated in the current study. Carboplatin exposure was determined in a total of nine courses of chemotherapy in four patients with Wilms' tumour. Carboplatin exposures following initial dosing were less than 50% of the defined target area under the plasma concentration-time curve (AUC) in all four patients studied, with actual AUC values of between 31% and 45% of the target exposures. The use of real-time pharmacokinetic monitoring to guide dosing within a course of carboplatin treatment resulted in exposures within 15% of the target AUC in all patients. Using this information to guide dosing on additional courses of treatment in the same patient resulted in consistent exposures without the need for further monitoring or dose adjustment. These results indicate that real-time pharmacokinetic monitoring of carboplatin treatment plays a key role in ensuring that an appropriate exposure to carboplatin is achieved in children with bilateral nephrectomy. Carboplatin dosing based on patient body weight, or use of a fixed dose of carboplatin, would both be predicted to result in individual patients receiving unsatisfactory drug exposures. Further studies are warranted to further elucidate the relationship between non-renal clearance of carboplatin and patient body weight in this and other patient subpopulations where there remains concern about the optimal way to use this anticancer drug.

Feasibility of combination chemotherapy with cisplatin and etoposide for haemodialysis patients with lung cancer

Cancer chemotherapy for haemodialysis patients has never been established. To elucidate the feasibility of cisplatin-based combination chemotherapy for haemodialysis patients with lung cancer, a dose escalation study was conducted. Five haemodialysis patients with lung cancer were treated with cisplatin and etoposide. A starting dose of 40 mg m(-2) of cisplatin on day 1 and 50 mg m(-2) of etoposide on days 1, 3 and 5 were administered as the first course for the first patient. Membrane haemodialysis was regularly performed three times a week and soon after the completion of therapy. By monitoring toxicity and pharmacokinetics data, the dose was escalated course by course and patient by patient. Dose escalation was completed for the first two patients resulting in full-dose chemotherapy consisting of 80 mg m(-2) of cisplatin on day 1 and 100 mg m(-2) of etoposide on days 1, 3 and 5. Multiple courses of the full-dose chemotherapy were administered to the other three patients. Toxicity was manageable and tolerable for all. Pharmacokinetics data were comparable to those from patients with normal renal function, except for potential long-lasting higher levels of free platinum in the renal insufficiency group. In conclusion, this standard-dose combination chemotherapy was feasible even for haemodialysis patients.

Randomized cross-over clinical trial to study potential pharmacokinetic interactions between cisplatin or carboplatin and etoposide

AIMS

Cisplatin and carboplatin are often used in combination with etoposide. In a randomized cross-over study, the potential interaction between the two platinum drugs and the metabolism of etoposide was explored. In vitro investigations using human liver microsomes were also performed.

METHODS

Etoposide was administered to 15 patients over 3 days, with the platinum drug administered on day 2. The alternate platinum drug was administered on the second course. The pharmacokinetics of etoposide were determined on all 3 days of each cycle. The effect of platinum drugs on etoposide metabolism by human liver enzymes was explored in vitro.

RESULTS

Neither cisplatin nor carboplatin coadministration affected the pharmacokinetics of etoposide during cycle 1. When carboplatin was administered on course 2, etoposide AUC was 8% higher on day 2 compared with day 1 or day 3 (for day 2 vs day 3, 95% CI: -0.72, -0.08 mg ml(-1) min). In contrast, cisplatin on course 2 increased the AUC of etoposide (28%) on day 3 (day 3 vs day 1, 95% CI: 0.67, 2.09 mg ml(-1) min), with no effect on day 2. In vitro carboplatin and cisplatin (10-100 microm) inhibited the metabolism of etoposide, if rat liver microsomes were preincubated (30 min) with NADPH and the platinum complexes. With human liver microsomes a small effect on etoposide metabolism, but not on catechol formation, was observed.

CONCLUSIONS

The interaction between etoposide and platinum drugs is small and, given the pharmacokinetic variability seen with etoposide, the clinical impact is unlikely to be significant.

Prospective validation of renal function-based carboplatin dosing in children with cancer: A United Kingdom Children's Cancer Study Group Trial

PURPOSE

Carboplatin dosing in adults with cancer is based on renal function. The purpose of the current study was to validate a previously developed pediatric carboplatin-dosing formula.

PATIENTS AND METHODS

Thirty-eight pediatric patients were randomized to receive a carboplatin dose calculated according to surface area or a renal function-based dosing formula. On the next course of therapy, the alternative dosing method was used for each patient. Carboplatin pharmacokinetics (based on free plasma platinum concentrations) were measured after both courses.

RESULTS

The mean observed areas under the carboplatin concentration-versus-time curve (AUCs) after renal function- and surface area-based dosing were 98% and 95% of the target AUCs, respectively. The variation in the observed AUC was significantly less after renal function-based dosing (F test, P =.02), such that 74% of courses had an observed AUC within +/- 20% of the target value, versus 49% for courses after dosing according to surface area. Only one of 22 courses at the center with the most experience with renal function-based dosing was associated with an AUC outside +/- 20% of the target value, versus nine of 22 courses after surface area-based dosing in the same center. There was a relationship (r(2) =.71) between carboplatin AUC and thrombocytopenia in 10 neuroblastoma patients treated with a combination of carboplatin, vincristine, etoposide, and cyclophosphamide.

CONCLUSION

Renal function-based carboplatin dosing in children results in more consistent drug exposure than surface area-based drug administration.

A study of the feasibility and accuracy of pharmacokinetically guided etoposide dosing in children

Pharmacokinetically guided dosing was performed in nine paediatric patients receiving etoposide. Doses on day 2 of a 2- or 3-day schedule were adapted on the basis of the day-1 area under the plasma etoposide concentration vs time curve (AUC). The day-1 AUC was estimated using a limited sampling model and the day-2 target AUC defined by the etoposide dose-AUC relationship observed in 33 children. Target AUC values (4.6-8.2 mg ml(-1) x min) were achieved with a high degree of precision and with little bias (mean error 11% and root mean squared error 15% respectively). Pharmacokinetic parameters were similar to those reported previously in children, although interpatient pharmacokinetic variability was less than that observed previously: plasma clearance, 23 (18-26) ml min(-1) m(-2); volume of distribution at steady state (Vdss), 6.0 (3.9-8.9) l m(-2); t(1/2) 254 (127-550) min (median and range). This study has demonstrated that pharmacokinetically guided dosing with etoposide is feasible. However, pharmacokinetically guided dosing is likely to be of most benefit in patients with abnormalities of renal or hepatic function, or in children with prior exposure to cisplatin.