Carboplatin Clearance Research Articles

Adjustment of creatinine clearance improves accuracy of Calvert's formula for carboplatin dosing.

Carboplatin clearance depends on the glomerular filtration rate (GFR), and Calvert's formula is frequently used to achieve a target area under the time vs concentration curve (mg ml(-1) min). Creatinine clearance is a substitute for GFR when creatinine values are determined by the Jaffé method, which is being replaced by the enzymatic method. When the enzymatic method is used, the corresponding creatinine clearance theoretically exceeds GFR, and the use of creatinine clearance as GFR in Calvert's formula results, accordingly, in overdosing of carboplatin. In this study, we have established a model for adjusting the creatinine clearance to offset this bias based on a relationship between creatinine values measured by the Jaffé method and by the enzymatic method: adjusted creatinine clearance (ml min(-1)) = creatinine clearance (ml min(-1)) x [serum creatinine (mg dl(-1))]/[serum creatinine (mg dl(-1)) + 0.2]. Subsequently, we validated this model using the data from 35 lung cancer patients. Estimated clearances of carboplatin with the original equation [creatinine clearance + 25] were systematically higher than observed clearances [mean prediction error (MPE) +/- standard error (s.e.) = 26 +/- 5%]. This positive bias was corrected by the adjustment (MPE +/- s.e. = 5 +/- 4%). When the enzymatic method is used, the adjusted creatinine clearance should be used in Calvert's formula.

1123 - Is Chatelut formula applicable in obese patients for predicting carboplatin clearance?

1123 - Is Chatelut formula applicable in obese patients for predicting carboplatin clearance?

219 Prediction of carboplatin clearance on Japanese lung cancer patients

219 Prediction of carboplatin clearance on Japanese lung cancer patients

How to predict carboplatin clearance from standard morphological and biological characteristics in obese patients

We previously proposed a formula to predict carboplatin clearance (CL) from four patient characteristics: plasma creatinine level, body weight, age, and sex (J Natl Cancer Inst 1995; 87: 573). Its accuracy was studied in a subpopulation of obese patients. Twenty-five patients (16 male and 9 female, 23 to 82 years old) were studied. They were 20% to 67% (median 36%) over the ideal weight which was calculated according to the Lorentz equation. Their actual CL was obtained individually by the Siphar program. The pharmacokinetic population program NONMEM was used to determine the best value of substitution for weight in the formula. By using the actual weight, CL was significantly over predicted (by more than 20% for 7 of 25 patients). By using the mean value between the ideal and the actual weight, a good prediction of CL was obtained: the percentage of error ranged from -21% to +22%. The formula is applicable to obese patients if both ideal and actual weights are taken into account.

Carboplatin pharmacokinetics in young children with brain tumors

The pharmacokinetic parameters and maximal tolerated systemic exposure were determined for carboplatin in young children given in combination with cyclophosphamide and etoposide. Carboplatin was administered as part of a multiagent chemotherapy regimen to 21 pediatric patients less than 5 years of age with newly diagnosed, malignant central nervous system tumors. Patients, received cyclophosphamide, 1.2 g/m2, on day 1 and carboplatin on day 2 followed by etoposide, 100 mg/m2, each day. Carboplatin doses were calculated to achieve a targeted area under the serum concentration versus time curve (TAUC) of 5, 6.5 or 8 mg/ml.min based on each patient's measured glomerular filtration rate (GFR). Carboplatin pharmacokinetic parameters were determined after course 1 and then after every third course of therapy. The median carboplatin clearance and GFR after course 1 were 118 and 98 ml/min per m2, respectively. Targeted doses based on measured GFR reliably achieved the TAUC for carboplatin. The median (range) carboplatin clearance for four children less than 1 year of age was 76 (66-84) ml/min per m2, significantly lower (P = 0.05) than the value of 131 (80-158) ml/min per m2 for children from 1 to 4 years of age. The mean carboplatin clearance declined by 23% in 12 patients studied from course 1 to course 4 of therapy. The decrease was greater than 20% (range 20-53%) in 7 of the 12 patients studied. Carboplatin clearance for children aged between 1 and 4 years at diagnosis is approximately 45% higher than previously reported for pediatric patients, but declines after four courses of therapy. For children less than 1 year of age, carboplatin clearance per square meter is approximately 40% lower than patients 1 to 4 years of age. There are corresponding differences in GFR that provide a plausible explanation for the age and therapy-related changes in carboplatin clearance. Toxicity was acceptable for patients treated at a TAUC of 6.5 mg/ml.min for carboplatin given with etoposide and cyclophosphamide. The average carboplatin dose required for this AUC was 767 mg/m2.

The use of the Calvert formula to determine the optimal carboplatin dosage.

Carboplatin is a chemotherapeutic agent frequently used in the treatment of various malignancies. The myelotoxicity and clinical efficacy of carboplatin correlate with the clearance of the drug, which is correlated to the glomerular filtration rate (GFR). Dosing of this agent based solely upon the patients body surface area is therefore not accurate enough; the GFR, and thus the clearance of carboplatin differ in each patient irrespective of the body area. Consequently, some patients undergo a higher systemic exposure, expressed as the area under the plasma concentration/time curve (AUC), than others when dosages of carboplatin are given on the basis of the body surface area. A high AUC correlates with increased toxicity, thus increasing the risks of the treatment, but in the case of a low AUC the therapeutical efficacy decreases. This indicates that an individual dosing strategy is warranted to obtain the optimal AUC. In this article, the development and application of a simple equation, known as the Calvert formula, are discussed. This formula can be used to calculate the carboplatin dose accurately in order to obtain a target AUC by using only the GFR. The formula is: dose (mg) = AUC (mg ml-1 min) x [GFR (ml/min) + 25 (ml/min)]. This formula has proven to be, in both retrospective and prospective studies, a reliable tool to calculate the optimal dose of carboplatin Future studies should determine the value of the creatinine clearance as a measure for the GFR.

Evaluation of formulas using the serum creatinine level to calculate the optimal dosage of carboplatin.

Carboplatin is a chemotherapeutic agent frequently used in the treatment of various malignancies. An individual dosing strategy has been recommended to yield the most optimal exposure, expressed as the area under the concentration-time curve (AUC). The formula developed by Calvert et al. (dose = target-AUC x [GFR + 25]) can be used to achieve this. However, due to the inconvenient [51Cr]-ethylenediamine-tetraacetic acid ([51Cr]-EDTA)-based measurement of the glomerular filtration rate (GFR), its application in the clinic has thus far been limited. Chatelut and co-workers have recently proposed a formula to estimate carboplatin clearance using the serum creatinine concentration. We retrospectively tested the Chatelut equation and the Calvert formula using either the creatinine clearance based on 24-h urine collection or the creatinine clearance based on the formula of Cockcroft and Gault. The latter equations were shown to predict the carboplatin clearance reasonably well, although systematic overprediction and underprediction occurred. However, the formula proposed by Chatelut and co-workers had no significant bias and was precise. It is proposed that this formula be used to calculate the optimal carboplatin dosage after prospective validation has been performed.

Prediction of Carboplatin Clearance From Standard Morphological and Biological Patient Characteristics

Hematologic toxicity of an antineoplastic drug, carboplatin, is largely dependent on its pharmacokinetics. Its therapeutic efficacy may be related to plasma drug exposure. Dosage adjustment based on isotopic determination of glomerular filtration rate has been proposed, but its ambulatory use is not yet conceivable. The dosage adjustment based on a patient's creatinine clearance relies on accurate measurement of urine volume per unit time and can be done with ease. A population pharmacokinetics study was undertaken to determine a relationship between carboplatin clearance and patient characteristics. A predictive formula was derived that was then prospectively evaluated, and its outcome was compared with that obtained by other methods available to predict carboplatin clearance. Plasma carboplatin pharmacokinetics determined as ultrafilterable platinum in 70 patients (age range, 23-84 years) treated with different combination regimens that included carboplatin at doses ranging from 184 mg to 950 mg (1-hour intravenous infusion) for various tumor types. Data were analyzed using the nonlinear mixed effects model (NONMEM). The data from 34 patients (46 cycles) were utilized to derive the most predictive formula. The reliability of the formula was subsequently evaluated by analyzing the data obtained from 36 other patients (49 cycles). Carboplatin clearance (mL/min) was found to be best predicted by the following formula: 0.134.weight + [218.weight.(1-0.00457.age).(1-0.314.sex)]creatinine expressed in micromolar concentration (with weight in kg, age in years, and sex = 0 if male and sex = 1 if female). Prospectively, this formula predicted the carboplatin clearance with good precision (median absolute percent error of 10% [range, 0% to 30%]) and minimal bias (median percent error of 2% [range, -25% to 30%]). This method of prediction was as accurate as the one derived from the measurement of glomerular filtration rate following the injection of 51 chromium-EDTA. This formula for the determination of carboplatin clearance can permit individualized determination of carboplatin dosage in adults by simply multiplying the calculated carboplatin clearance by the area under the curve for the desired dosage administration.

Carboplatin pharmacokinetics in children: the development of a pediatric dosing formula. The United Kingdom Children's Cancer Study Group.

The aim of this study was to define the pharmacokinetics of carboplatin in children and use the data to develop a pediatric dose formula. It was anticipated that renal function would be a major determinant of carboplatin disposition and the relationship between carboplatin clearance and glomerular filtration rate (GFR) was examined in detail. Plasma carboplatin pharmacokinetics were measured as ultrafiltrable platinum in 22 patients (5 to 63 kg) following 200 to 1,000 mg/m2 of carboplatin. GFR was measured by the plasma clearance of chromium 51-edathamil (51Cr-EDTA). Carboplatin pharmacokinetics in children were best described in most patients (16 of 22) by a two-compartment model. The dose-normalized area under the plasma carboplatin concentration versus time curve (AUC) ranged from 3.1 to 9.6 mg/mL.min/400 mg/m2 and there was only a weak linear relationship between carboplatin dose and AUC (R2 = .31). There was a significant relationship between absolute carboplatin and 51Cr-EDTA clearances (R2 = .56), but the relationship was weaker (R2 = .28) when both clearances were normalized for body surface area. Carboplatin plasma clearance was predicted by the equation: clearance = GFR (mL/min) + 0.36 x body weight (BW; kg), and a modified form of the adult carboplatin dose formula is proposed: dose (mg) = target AUC x (GFR [mL/min] + [0.36 x BW(kg)]). Two further equations were developed that use the 51Cr-EDTA half-life (t1/2) to calculate the GFR and these may reduce errors resulting from inaccurate measurement of the volume of distribution for 51Cr-EDTA. In patients treated with single-agent carboplatin or carboplatin plus vincristine, there was a significant sigmoidal relationship between AUC and thrombocytopenia (R2 = .56). GFR-based carboplatin dosing in children should be feasible and will be evaluated prospectively.

Pharmacokinetics and acute renal effects of continuously infused carboplatin

Carboplatin was given as a 24-hour infusion at high doses to pediatric patients with cancer (n = 11) and pharmacokinetic parameters and renal effects were determined. Median carboplatin clearance for course 1 (151 ml/min per 1.73 m2;) was not significantly different from clearance for course 2 (144 ml/min per 1.73 m2; p = 0.33). The median glomerular filtration rate measured before (159 ml/min per 1.73 m2) and after course 1 (161 ml/min per 1.73 m2) did not differ significantly (p = 0.4). Binding was time dependent but modest with a median free fraction at the end of infusion of 0.82. Pharmacokinetic parameters for continuous-infusion carboplatin are similar to those reported for short infusions, but the median dose of 817 mg/m2 required to achieve an acceptable systemic exposure in these patients was 45% greater than the previously suggested maximum tolerated dosage. Continuous infusion carboplatin did not alter carboplatin clearance or adversely effect glomerular filtration rate during a second course, showing the feasibility of this alternative dosage strategy to enhance therapeutic effects.

The pharmacokinetics of high-dose carboplatin in pediatric patients with cancer.

Carboplatin disposition was studied in 18 pediatric patients with cancer over a dosage range of 400 to 700 mg/m2 given on an alternate-day schedule (total doses of 1200 to 2100 mg/m2) with high-dose etoposide. Median age was 7.7 years, hepatic functions were normal, and serum creatinine levels were less than or equal to 1.0 mg/dl. Carboplatin pharmacokinetics were determined by atomic absorption spectroscopy. Median pharmacokinetic parameters for ultrafilterable platinum were as follows: clearance 45.8 ml/min/m2 (range, 25.5 to 65.3 ml/min/m2) and a terminal half-life of 3.6 hours (range, 2.1 to 14.2 hours). Carboplatin clearance (CL) values and volume of distribution (VC) were highly correlated to body size (CL = 55 x Body surface area in [BSA, in square meters] - 6.7, r2 = 0.73; VC = 5 x BSA [in square meters] + 0.26, r2 = 0.69). However, carboplatin doses normalized to BSA still resulted in twofold to threefold variability in area under the concentration-time curve. Carboplatin CL was significantly lower in those subjects (n = 9) who had previously received cumulative cisplatin doses of greater than or equal to 960 mg/m2 (p less than 0.05) but was not influenced by age, gender, or diagnosis.

Comparison of methods of assessment of renal function in patients with cancer treatedwith cisplatin, carboplatin or methotrexate

In patients with cancer treated with cisplatin, carboplatin or methotrexate creatinine clearance calculated using the Cockcroft-Gault formula was compared with measured clearance and with the glomerular filtration rate. In 106 patients the average squared difference for calculated and 24 hour urine creatinine clearance was 0.288, n = 606; and for calculated creatinine clearance and glomerular filtration rate (measured using diethylenetriaminepenta-acetic acid, DTPA), 0.212, n = 34. On 35 of 606 occasions (6%) in 18 patients (17%), the calculated clearance overestimated the 24-hour urine creatinine clearance when it was less than 1 mL/s. In all but one patient, this was explained by factors leading to renal impairment (seven patients) or overestimation of clearance (ascites in two patients) or by an isolated low value of 24-hour urine creatinine clearance (eight patients). Declining renal function with increasing total dose of cisplatin was detected by both calculated and 24-hour urine creatinine clearance in patients with germ cell tumours. Derivation of an equation to predict creatinine clearance showed a linear association with plasma creatinine concentration, patient age, weight and gender. Variability in cancer patients was similar to that in the original Cockcroft-Gault study. Calculation of creatinine clearance can be used in cancer patients to monitor treatment with renally-eliminated chemotherapy agents.

Carboplatin and etoposide pharmacokinetics in patients with testicular teratoma

The pharmacokinetics of carboplatin and etoposide were studied in four testicular teratoma patients receiving four courses each of combination chemotherapy consisting of etoposide (120 mg/m2 daily x 3); bleomycin (30 mg weekly) and carboplatin. The carboplatin dose was calculated so as to achieve a constant area under the plasma concentration vs time curve (AUC) of 4.5 mg carboplatin/ml x min by using the formula: dose = 4.5 x (GFR + 25), where GFR is the absolute glomerular filtration rate measured by 51Cr-EDTA clearance. Carboplatin was given on either day 1 or day 2 of each course and pharmacokinetic studies were carried out in each patient on two courses. Etoposide pharmacokinetics were also studied on two separate courses in each patient on the day on which carboplatin was given and on a day when etoposide was given alone. The pharmacokinetics of carboplatin were the same on both the first and second courses, on which studies were carried out with overall mean +/- SD values (n = 8) of 4.8 +/- 0.6 mg/ml x min, 94 +/- 21 min, 129 +/- 21 min, 20.1 +/- 5.41, 155 +/- 33 ml/min and 102 +/- 24 ml/min for the AUC, beta-phase half-life (t 1/2 beta), mean residence time (MRT), volume of distribution (Vd) and total body (TCLR) and renal clearances (RCLR), respectively. The renal clearance of carboplatin was not significantly different from the GFR (132 +/- 32 ml/min). Etoposide pharmacokinetics were also the same on the two courses studied, with overall mean values +/- SD (n = 8) of: AUC = 5.1 +/- 0.9 mg/ml x min, t 1/2 alpha = 40 +/- 9 min, t 1/2 beta = 257 +/- 21 min, MRT = 292 +/- 25 min, Vd = 13.3 +/- 1.31, TCLR = 46 +/- 9 ml/min and RCLR = 17.6 +/- 6.3 ml/min when the drug was given alone and AUC = 5.3 +/- 0.6 mg/ml x min, t 1/2 alpha = 34 +/- 6 min, t 1/2 beta = 242 +/- 25 min, MRT = 292 +/- 25 min, Vd = 12.5 +/- 1.81, TCLR = 43 +/- 6 ml/min and RCLR = 13.4 +/- 3.5 ml/min when it was given in combination with carboplatin. Thus, the equation used to determine the carboplatin accurately predicted the AUC observed and the pharmacokinetics of etoposide were not altered by concurrent carboplatin administration. The therapeutic efficacy and toxicity of the carboplatin-etoposide-bleomycin combination will be compared to those of cisplatin, etoposide and bleomycin in a randomised trial.

Pharmacokinetics of carboplatin after intraperitoneal administration.

The pharmacokinetics of carboplatin, ultrafilterable platinum, and total platinum after intraperitoneal (i.p.) administration were studied in peritoneal fluid, plasma, red blood cells (RBCs), and urine during a phase-I trial in patients with minimal, residual ovarian cancer. Samples were collected from 7 patients who had received carboplatin (200-500 mg/m2) in 21 dialysis fluid. The fluid was withdrawn after a 4-h dwell. Platinum concentrations were measured by flameless atomic absorption spectrometry, and intact carboplatin was determined by HPLC with electrochemical detection. Peak concentrations of carboplatin in plasma were obtained 2 h after the end of instillation. The mean ratio of peak concentrations of carboplatin in instilled fluid and plasma was 24 +/- 11. The peritoneal clearance of carboplatin was 8 +/- 3 ml/min, which was 12 times less than the plasma clearance (93 +/- 32 ml/min). Due to this clearance ratio, the AUCs for the peritoneal cavity were about 10 times higher than those for plasma. On average, 34% +/- 14% of the dose was still present in the instillation fluid that had been withdrawn after a dwell time of 4 h. In plasma, the mean value of AUC/Dnet (Dnet = Dose - amount recovered from the peritoneal cavity) after i.p. administration was comparable with that of AUC/D after i.v. administration. This means that unrecovered carboplatin (66%) was completely absorbed from the peritoneal cavity. It may be expected from this bioavailability that the maximum tolerated dose (MTD) of i.p.-administered carboplatin with a 4-h dwell is around 1.5 times higher than that after i.v. administration. Overall pharmacokinetic parameters of carboplatin and platinum in plasma were comparable after i.p. and i.v. administration.

Pharmacokinetics of unchanged carboplatin (CBDCA) in patients with small cell lung carcinoma.

The disposition of the cisplatin analogue carboplatin was studied in seven patients with small cell lung cancer. Carboplatin 100 mg/m2 was administered without hydration by a 1-h infusion with VP16-213 120 mg/m2 on days 1, 2 and 3 of each course. Plasma and urine collections were made on days 1 and 3 of the first course of treatment. Carboplatin levels in plasma ultrafiltrate and urine were quantitated using a specific and sensitive, high-performance liquid chromatographic assay which involved sample clean-up on a Dowex-2 column prior to injection. Estimates of pharmacokinetic parameters determined using either compartmental or non-compartmental methods were comparable. There was no difference between carboplatin pharmacokinetic parameters determined on days 1 and 3 of treatment. The mean (+/- SD) carboplatin half-life determined from plasma data on day 1 was 105 +/- 30.4 min and was not significantly different from that determined using urinary excretion rate data (107 +/- 51.7 min). Urinary excretion rate plots showed that carboplatin elimination was mono-exponential for up to 14 h after infusion. Total-body clearance was 105 +/- 40.0 ml min-1 m-2, renal clearance 64.3 +/- 44.1 ml min-1 m-2, and volume of distribution 17.3 +/- 4.2 l/m2 on the 1st day of treatment. Of the administered dose, 58.4% +/- 21.2% was recovered in urine over a 24-h period after the start of the infusion. The mean renal clearance of carboplatin was comparable to creatinine clearance. Carboplatin disposition was clearly defined in the patients studied using analytical methodology specific for the unchanged drug.