Pharmacokinetics of very high-dose oral melphalan in cancer patients

The pharmacokinetics and systemic availability of melphalan after high-dose oral administration with and without 1,3-bis(2-Chloroethyl)-1-nitrosourea (BCNU) or etoposide were examined in three patients undergoing autologous bone marrow transplantation. Patient 1 (advanced melanoma) received melphalan at 80 mg/m2/day p.o. on days -6, -5, and -4, followed by BCNU at 300 mg/m2/day i.v. on days -3, -2, and -1 prior to bone marrow transplantation. Patient 2 (advanced colon carcinoma) received melphalan at 75 mg/m2/day p.o. on days -3, -2, and -1. Patient 3 (advanced refractory lymphoma) received etoposide at 800 mg/m2/day i.v. on days -7, -5, and -3, followed by melphalan at 157 mg/m2/day p.o. on days -2 and -1. Melphalan was administered as a bolus oral dose, using 2-mg tablets. Blood samples were collected at 0, 5, 10, 15, 30, and 45 min and 1, 2, 3, 4, 6, 8, 12, and 24 h after each dose of melphalan. Peak plasma melphalan concentrations in the three patients ranged from 0.354 (patient 2) to 1.768 micrograms/ml (patient 1). Plasma melphalan concentration X time products (C x Ts) showed extreme variability in one patient (patient 2), ranging from 0.76 to 4.48 micrograms.h/ml. To determine the relative systemic availability of orally administered melphalan, i.v. C X Ts proportional to the p.o. doses were extrapolated from previously reported i.v. bolus pharmacokinetic data. The p.o.:i.v. plasma C X T ratios for high-dose melphalan ranged between 0.09 (patient 3) and 0.58 (patient 2). Although these C X T data suggest a dose-response for orally administered melphalan, the systemic availability of these high p.o. melphalan doses was extremely variable, both within and between study patients. Thus, we cannot recommend the use of high-dose p.o. melphalan regimens in patients undergoing autologous bone marrow transplantation.     

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

Two patients with relapsed Wilms'' tumour and renal failure requiring dialysis were given carboplatin and etoposide by pharmacokinetically guided dosing. The target area under the drug plasma concentration vs time curve (AUC) was 6 mg ml-1 min for carboplatin and 18 and 21 mg ml-1 min for etoposide. On course 1 measured AUCs of carboplatin and etoposide were 6 and 20 mg ml-1 min for patient 1 and 6 and 21 mg ml-1 min for patient 2 respectively. Peritoneal dialysis did not remove carboplatin or etoposide from the plasma, however carboplatin but not etoposide was cleared by haemodialysis. Therapy with carboplatin and etoposide is possible in children and adults with renal failure who require dialysis, but in this situation pharmacokinetic monitoring is essential.     

Plasma pharmacokinetics of high-dose oral melphalan in patients treated with trialkylator chemotherapy and autologous bone marrow reinfusion

The pharmacokinetics of melphalan following high-dose p.o. administration were determined in 17 patients with various malignancies for the purpose of assessing interpatient and intrapatient pharmacokinetic variability. All patients underwent bone marrow harvest on day -8 (relative to bone marrow reinfusion). On days -7, -6, and -5, melphalan was given p.o. and the dose was escalated on each cohort consisting of at least 3 patients (beginning at 0.75 mg/kg). On days -6, -4, and -2, cyclophosphamide at 2.5 g/m2 and thiotepa at 225 mg/m2 were given i.v. On day -7 the peak melphalan concentration was 1.64 +/- 0.89 (SD) microM with a terminal half-life of 1.56 +/- 0.86 h. The area under the plasma concentration time curve (AUC) and oral clearance were 217.9 +/- 115.1 microM/min and 30.2 +/- 14.2 ml/min/kg. There was only a moderate correlation between the melphalan dose and both the peak concentration (r = 0.50, P less than 0.05) and AUC (r = 0.64, P less than 0.01) over the dosage range of 0.75-2.5 mg/kg. There was a trend towards greater interpatient variability in peak concentration, AUC, and oral clearance observed at the higher doses of melphalan. Analysis of intrapatient pharmacokinetic variability in 8 patients showed a significant difference between the doses given on days -7 and -5 in the peak concentration (2.09 versus 1.07 microM, P = 0.02), AUC (264.9 versus 134.8 microM/min, P = 0.01), and oral clearance (25.1 versus 53.1 ml/min/kg, P = 0.05) but no significant difference in the time to peak and terminal half-life. We conclude that there is marked interpatient and intrapatient variability in melphalan pharmacokinetics following high-dose p.o. administration. The data are consistent with saturable absorptive pathways for melphalan, which might be especially sensitive to concurrent high-dose chemotherapy.     

Etoposide pharmacokinetics in patients with normal and abnormal organ function

Precise guidelines for dose modification of etoposide in patients with hepatic dysfunction have not been determined. Etoposide pharmacokinetics were determined in 17 patients. Nine patients had bilirubin less than or equal to 1 mg/dL and eight had bilirubin ranging from 1.9 to 23 mg/dL. Twelve patients received etoposide 100 mg/m2 days 1, 3, and 5, in combination with cisplatin 70 mg/m2 or iproplatin 225 mg/m2 on day 1. Five patients received only one dose of etoposide. Etoposide was measured using a published high pressure liquid chromatography (HPLC) method which also quantitates picro etoposide and its hydroxy acid. Systemic clearance, Vdss and t1/2 beta averaged (+/- SD) 21.4 (+/- 7.4) mL/min/m2, 10.7 (+/- 4.1) L/m2, and 8.1 (+/- 2.8) hours in the nine patients with bilirubin less than or equal to 1 mg/dL, and 22.4 (+/- 9.6) mL/min/m2, 13.6 (+/- 11.3) L/m2, and 8.4 (+/- 3.9) hours in the eight patients with bilirubin 1.9 to 23.0 mg/dL. Stepwise multiple linear regression analysis of liver and renal function tests and other patient-specific variables identified creatinine clearance as the strongest predictor of etoposide systemic clearance (r2 = 40.8). Serum albumin was identified as the next strongest predictor, improving the r2 to 57.3%. Cumulative biliary excretion of unchanged etoposide and glucuronide or sulfate conjugates over 48 hours accounted for less than 3% of the dose in six patients studied. Toxicity occurred in patients with normal and abnormal bilirubin and was unrelated to etoposide clearance. Patients with total bilirubin 1.9 to 23 mg/dL, but creatinine clearance greater than 30 mL/min/m2 had etoposide clearance within the range for patients with normal liver function (16.8 to 35 mL/min/m2). Although these patients did not have reduced etoposide clearance, the major routes of etoposide non-renal elimination remain to be clearly defined. Additional patients should be evaluated to establish more precise guidelines for dosing etoposide in patients with abnormal liver function.     

Pharmacokinetic study of etoposide in aged patient with non Hodgkin lymphoma receiving hemodialysis

A 78 year old patient with non Hodgkin Lymphoma receiving hemodialysis was treated with etoposide at a dose of 50 mg per body and its plasma pharmacokinetics were studied. The patient was dialyzed for 4 hours three times weekly. Etoposide was given by 60 minutes infusion on day 1 and 3, and hemodialysis was performed on day 2. The pharmacokinetic curve was found to fit to two compartment model. T 1/2 beta was 11.29 hours. Total body clearance was 13.65 mg/min/m2 on day 1 and 12.83 mg/min/m2 on day 3 respectively. AUC was 41.53 micrograms.h/ml on day 1 and 44.18 micrograms.h/ml on day 3 respectively. When these results were compared to those reported in patients with normal renal function, half life were longer while total body clearance was lower. In addition, AUC was higher. Hematologic toxicities were severe at this low dose. Hemodialysis did not influence on the decay of concentration during the elimination phase. These results suggest that it is necessary to reduce the dose of etoposide in hemodialysis patients.     

Dose finding study of oral PSC 833 combined with weekly intravenous etoposide in children with relapsed or refractory solid tumours

PSC 833 is an effective MDR1 reversal agent in vitro, including studies with paediatric cancer cell lines such as neuroblastoma and rhabdomyosarcoma. This study was performed to determine the safety profile, dose limiting toxicity (DLT) and maximum tolerated dose (MTD) in children with solid tumours and to determine the influence of PSC 833 on the pharmacokinetics of co-administered etoposide. Each patient received one cycle of intravenous etoposide (100 mg/m2 daily for 3 days on three consecutive weeks) to document baseline pharmacokinetics, and subsequently the same schedule using a dose of 50 mg/m2 was given combined with PSC 833 given orally every 6h at a starting dose of 4 mg/kg. Thirty two eligible patients (23 male, median age 8.3 years) were enrolled. Neuroblastoma and rhabdomyosarcoma were the common disease types. Brain tumours were excluded. DLT was defined as any non-haematological grade 3-4 toxicity (common toxicity criteria) and using a specific toxicity scale for cerebellar toxicity. The MDT was defined as the first dose below which 2 or more patients per dose level experienced DLT. Grade 1-2 ataxia occurred in cohorts 2 and 3 (4 and 5 mg/kg, respectively). Three patients developed grade 3 neurotoxicity in the 6 mg/kg cohort and this defined the MTD. Six responses were observed (2 CR, 4 PR). Pharmacokinetic studies indicated that the clearance of etoposide was reduced by approximately 50% when combined with PSC 833. It is concluded that the toxicity profile and MDT is similar in both children and adults, as is the effect on etoposide metabolism. The study demonstrated the feasibility and safety of carrying out a paediatric phase 1 trial across European boundaries and acts as a model for future cooperative studies in rare cancers among children.     

Randomized comparison of etoposide pharmacokinetics after oral etoposide phosphate and oral etoposide.

Etoposide phosphate is a water-soluble prodrug of etoposide. The plasma pharmacokinetics of etoposide following oral administration of etoposide phosphate or oral etoposide were compared. Seventeen patients with solid tumours were enrolled to receive oral etoposide phosphate 125 mg m(-2) on days 1-5 every 3 weeks, with escalation to 175 mg m(-2) from course 3 when possible. Patients were randomized to receive oral etoposide phosphate or oral etoposide on day 1 of course 1 and the alternative compound on day 1 of course 2. Fifteen patients received two or more courses and were evaluable for pharmacokinetic comparisons. The median AUC(inf) (area under the concentration vs time curve from zero to infinity) of etoposide was 77.7 mg l(-1) h after etoposide phosphate (95% CI 61.3-100.5) and 62.0 mg l(-1) h after oral etoposide (95% CI 52.2-76.9). The difference in favour of etoposide phosphate was borderline significant: median 9.9 mg l(-1) h (95% CI 0.1-32.8 mg l(-1) h; P = 0.05). However, the inter-patient variability of etoposide AUC(inf) was not improved (coefficients of variation 42.3% and 48.4%). Etoposide phosphate was undetectable in plasma after oral administration. Toxicities of oral etoposide phosphate were not different from those known for etoposide. In conclusion, oral etoposide phosphate does not offer a clinically relevant benefit over oral etoposide.     

Carboplatin and etoposide pharmacokinetics in patients with testicular teratoma

Summary 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×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×(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), 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=40±9 min, t_1/2=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=34±6 min, t_1/2=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-etoposidebleomycin combination will be compared to those of cisplatin, etoposide and bleomycin in a randomised trial.     

High-dose melphalan, misonidazole, and autologous bone marrow transplantation for the treatment of metastatic colorectal carcinoma. A phase I study

To augment the antitumor effect of high-dose melphalan and determine pharmacokinetics we conducted a phase I trial of escalating doses of high-dose IV melphalan with the chemosensitizer misonidazole for patients with advanced colorectal carcinoma. Fourteen patients with modified Dukes D adenocarcinoma of the colorectum were treated with a single course of melphalan (40-60 mg/m2 i.v. bolus q.d. X 3 days) and misonidazole (1-3 g/m2 p.o. q.d. X 3 days) followed by autologous bone marrow transplantation. Toxicity consisted of severe myelosuppression, moderate nausea and vomiting, and mild mucositis and diarrhea. One patient developed unexplained renal tubular acidosis, and a diffuse encephalopathy occurred in another patient. Three patients died within the first 30 days after the start of treatment, two due to tumor progression and one due to sepsis and disseminated intravascular coagulation-induced intracerebral hemorrhage. Six of 14 patients achieved a partial response, and the median response duration was 4 months (range 3-10 months). Analysis of misonidazole serum concentrations showed similar pharmacokinetics to those previously reported, suggesting no significant drug interaction with intravenous melphalan. Mean peak serum concentrations ranged from 81.8 micrograms/ml to 115.2 micrograms/ml at the second and third misonidazole dose levels, which approximate those known to provide effective chemosensitization with melphalan in animal models. In this phase I study, we showed that maximally tolerated doses of intravenous melphalan can safely be combined with oral misonidazole. In view of the large volumes of oral misonidazole required at the highest dose level, subsequent studies to determine the maximally tolerated dose of misonidazole should employ the intravenous form.     

A clinical and pharmacokinetic study of isolated limb perfusion with heat and melphalan for melanoma

The pharmacokinetics of isolated limb perfusion were studied to see what melphalan concentrations were achieved and how effective the isolation was. Twenty-eight patients received 32 limb perfusions with heat and melphalan for locally recurrent or level V melanoma. Melphalan was given 0.75 mg/kg for axillary/popliteal or 1.2 mg/kg for femoral perfusions with heat (perfusate 42 degrees C, limb 40 degrees C) for 1 hour. Melphalan concentratives were measured by high-performance liquid chromatography in seven patients. Peak perfusate melphalan concentrations were 6.1 to 115 mg/ml, which was one to two logs higher than peak systemic concentratives of melphalan. Isolation of the perfusate circuit from the systemic circulation was better for axillary and popliteal perfusions than for femoral perfusions (P less than 0.05). Complete responses were seen in 81% of evaluable patients; long-term local control was achieved in most patients, although many developed hematogenous metastases. Toxicity included erythema and edema in all, mild leukopenia in two, neuropathy in two, and amputation was required in one patient. Improvements in surgical technique include regional anesthesia to reduce vasospasms and transcutaneous measurement of fluorescein to measure leak. Perfusion with heat and melphalan remains the treatment of choice for in-transit metastases from melanoma.     

Dose Intensification of Etoposide in the BEAM ABMT Protocol for Malignant Lymphoma

We have previously demonstrated a dose response relationship in Hodgkin's disease for the combination of BCNU, VP16, Ara C and Melphalan, with the superior efficacy of the BEAM regimen requiring haemopoietic support, compared with miniBEAM.^1,2 To further exploit this, we have attempted to escalate the VP16 dose in BEAM. The standard etoposide dose is 200 mg/m² IV for four days. Thirty seven patients with refractory lymphoma received 400 mg/m²/day of etoposide, and 13 patients 600 mg/m²/day, in addition to BCNU, cytarabine, and melphalan. Toxicity and outcome parameters were compared in the preceeding 40 patients, who received 200 mg/m²/day etoposide. The toxic mortality with 400 mg/m²/day of etoposide (3%) was identical to that for the standard BEAM regimen (5%). Two procedure related deaths occurred in the highest VP16 dose group (15%). The morbidity of the lower etoposide dose regimens was comparable, but 600 mg/m²/day induced significantly greater gastrointestinal toxicity. Twelve of the 13 patients receiving this dose suffered grade II-IV mucositis, with stomatitis, dysphagia and prolonged diarrhoea; 5 haemodynamically significant gastrointestinal haemorrhage, and 1 fatal toxic colitis. Granulocyte colony stimulating factor did not influence the nonhaematological toxicity. The three month response rates were similar (91%) in all dose cohorts. The maximum tolerable etoposide dose within the BEAM regimen is thus 400 mg/m² for four days.     

Pharmacokinetics of high-dose melphalan in children and adults

Summary Melphalan pharmacokinetics were studied in 20 children with stage IV neuroblastomas or Ewing's sarcomas and in 10 adults with AML, ALL, or small cell lung carcinomas, after IV administration of high doses (140 mg/m² with furosemide-induced diuresis and 180 mg/m² without induced diuresis) and high fluid intake (3000 ml/m²/day).Unchanged melphalan was assayed in plasma and cereorospinal fluid by means of a high-performance liquid chromatographic procedure. The elimination half-life (t_1/280 min) allows autologous bone marrow transplantation 24 h after the drug administration. In some children we were able to detect melphalan in cerebrospinal fluid samples.     

Pharmacokinetics of melphalan in clinical isolation perfusion of the extremities

The pharmacokinetics of melphalan in clinical hyperthermic isolation perfusion was studied in 16 patients with malignant melanoma. Analysis by computer-generated lines of best fit showed that the loss of melphalan from perfusate conforms best to a biexponential equation. The initial loss with a half-life (t1/2) of approximately 5 to 10 min is interpreted as rapid uptake of melphalan by the tissue of the perfused extremity. The terminal portion of the curve with a half-life of approximately 35 to 50 min is interpreted as due predominantly to the hydrolysis of melphalan, with a lesser component of loss due to absorption of melphalan to the filters and tubing of the perfusion apparatus. Determination of the area under the curve suggests that there is no appreciable uptake of melphalan by the tissue of the perfused extremity after 30 min.     

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.     

Pharmacokinetics of an etoposide infused over three days: concomitant infusion with cisplatin.

The pharmacokinetics of a 72-hour infusion of 240 mg/m2 etoposide administered concurrently with 90 mg/m2 cisplatin was studied in 12 lung cancer patients. The area under the curve (AUC), elimination half-life, steady state concentration, systemic clearance, renal clearance of etoposide and distribution volume at steady state were 225.4 +/- 39.2 micrograms x h/ml, 8.1 +/- 3.4 h, 3.1 +/- 0.6 micrograms/ml, 18.8 +/- 3.1 ml/min/m2, 3.1 +/- 1.4 ml/min/m2, 9.6 +/- 3.8 l/m2, respectively, which were in accordance with those reported previously in patients treated with etoposide alone. Although concentration at 24 hours, total bilirubin level and total protein level were correlated with the AUC which in turn correlated with hematologic toxicity, the variables were not predictive of hematologic toxicity. We conclude that the concomitant administration of cisplatin at a dose level of 30 mg/m2/day might not affect the pharmacokinetics of prolonged etoposide infusion.     

The pharmacokinetic advantages of isolated limb perfusion with melphalan for malignant melanoma.

We describe melphalan pharmacokinetics in 26 patients treated by isolated limb perfusion (ILP). Group A (n = 11) were treated with a bolus of melphalan (1.5 mg kg-1), and in a phase I study the dose was increased to 1.75 mg kg-1. The higher dose was given as a bolus to Group B (n = 9), and by divided dose to Group C (n = 6). Using high performance liquid chromatography (HPLC) the concentrations of melphalan in the arterial and venous perfusate (during ILP) and in the systemic circulation (during and after ILP) were measured. Areas under the concentration time curves for perfusate (AUCa, AUCv) and systemic (AUCs) data were calculated. In all three groups the peak concentrations of melphalan were much higher in the perfusate than in the systemic circulation. The pharmacokinetic advantages of ILP can be quantified by the ratio of AUCa/AUCs, median value 37.8 (2.1-131). AUCa and AUCv were both significantly greater in Group B than in Group A (P values less than 0.01, Mann-Whitney). In Groups B and C acceptable 'toxic' reactions occurred but were not simply related to melphalan levels. Our phase I study has allowed us to increase the dose of melphalan to 1.75 mg kg-1, but we found no pharmacokinetic advantage from divided dose administration.     

Increasing the effective concentration of melphalan in experimental rat liver tumours: comparison of isolated liver perfusion and hepatic artery infusion.

Regional chemotherapy allows further exploitation of the steep dose response curve of most chemotherapeutic agents, while systemic toxicity remains tolerable. We investigated the difference in maximally tolerated dose, pharmacokinetics and antitumour effect comparing administration of melphalan as a bolus in isolated liver perfusion (ILP) or via hepatic artery infusion (HAI). For these in vivo studies an experimental model for liver metastases in male WAG/Ola rats is obtained by subcapsular inoculation of CC531 rat colon carcinoma cells. In this system, ILP allowed administration of a two times higher dose than HAI (12 mg kg-1 vs 6 mg kg-1). In both treatment modalities systemic toxicity (leukopenia) was dose limiting. No hepatic toxicity was observed. Bolus administration of the maximally tolerated doses of melphalan in HAI (6 mg kg-1) and ILP (12 mg kg-1) resulted in four times higher concentrations in both liver and tumour tissue of the ILP treated rats. However, the ratio of mean drug concentration in liver vs tumour tissue appeared to be 1.5 times that found for HAI. In the range of the in tumour tissue measured melphalan concentrations the CC531 cells showed a steep dose response relationship in vitro. Whereas HAI resulted in significant tumour growth delay, complete remissions were observed in 90% of the rats treated with ILP. This study shows that with 12 mg kg-1 melphalan in ILP highly effective drug concentrations are achieved in CC531 tumour tissue; although the melphalan concentration in liver tissue shows an even higher increase than in tumour tissue, hepatic toxicity is negligible in this dose range.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics and pharmacodynamics of prolonged oral etoposide in women with metastatic breast cancer

The pharmacokinetics and pharmacodynamics of prolonged oral etoposide chemotherapy were investigated in 15 women with metastatic breast cancer who received oral etoposide 100 mg as a single daily dose for up to 15 days. There was considerable interpatient variability in the day 1 pharmacokinetic parameters: area under the plasma concentration time curve (AUC) (0–24 h) 1.95±0.87 mg/ml per min (mean ± SD), apparent oral clearance 60.9±21.7 ml/min per 1.73 m², peak plasma concentration 5.6±2.5 g/ml, time to peak concentration 73±35 min and half-life 220±83 min. However, intrapatient variability in systemic exposure to etoposide was much less with repeated doses. The intrapatient coefficient of variation (CV) of AUC for day 8 relative to day 1 was 20% and for day 15 relative to day 1 was 15%, compared to the day 1 interpatient CV of 45%. Neutropenia was the principal toxicity. Day 1 pharmacokinetic parameters were related to the percentage decrease in absolute neutrophil count using the sigmoidal E_max equation. A good fit was found between day 1 AUC and neutrophil toxicity (R ²=0.77). All patients who had a day 1 AUC>2.0 mg/ml per min had WHO grade III or IV neutropenia. The predictive performance of the models for neutrophil toxicity was better for AUC (percentage mean predictive error 5%, percentage root mean square error 18.1%) than apparent oral clearance, peak plasma concentration, or daily dose (mg/m²). A limited sampling strategy was developed to predict AUC using a linear regression model incorporating a patient effect. Data sets were divided into training and test sets. The AUC could be estimated using a model utilizing plasma etoposide concentration at only two time points, 4 h and 6 h after oral dosing (R ²=98.9%). The equation AUC_pr=–0.376+0.631×C_4h+0.336×C_6h was validated on the test set with a relative mean predictive error of –0.88% and relative root mean square error of 6.4%. These results suggest monitoring of AUC to predict subsequent myelosuppression as a strategy for future trials with oral etoposide.Division of Haematology and Medical Oncology, Peter MacCallum Cancer Institute, Locked Bag 1, A'Beckett St, Melbourne 3000, Australia     

Hyperthermia modifies pharmacokinetics and tissue distribution of intraperitoneal melphalan in a rat model

Background and objectives Peritoneal surface malignancy is a common manifestation of failure of treatment for abdominal cancers. Best results of treatment have been achieved with complete cytoreduction followed by heated intraoperative chemotherapy. Melphalan is a chemotherapeutic agent that shows increased pharmacological activity with heat. But the combination of intraperitoneal administration and heat have never been tested for this drug. The purpose of this study was to evaluate the effect of hyperthermia on the pharmacokinetics and tissue distribution of intraperitoneal melphalan in a rodent model.Methods Melphalan was given by the intraperitoneal route to 20 Sprague-Dawley rats at a dose of 12 mg/kg over 90 min. Rats were randomized into two groups according to the temperature of the peritoneal perfusate: group NT received normothermic (33.5°C) melphalan; group HT received hyperthermic (42°C) melphalan. During the course of intraperitoneal chemotherapy, peritoneal fluid and blood were sampled at 5, 15, 30, 60 and 90 min. At the end of procedure, the rats were killed and tissues samples (heart, liver, ileum, jejunum, colon, omentum, and abdominal wall) were collected. Concentrations of melphalan were determined in peritoneal fluid, plasma, and tissues by high-performance liquid chromatography.Results The area under the curve (AUC) of peritoneal fluid melphalan was significantly lower in the HT group than in the NT group (P=0.001), whereas no significant difference in plasma AUC was found. AUC ratios (AUC peritoneal fluid/AUC plasma) were 12.1 for the NT group and 12.3 for the HT group. The mean time to reach the plasma peak was shorter in the HT group than in the NT group (P=0.004). The HT group exhibited increased melphalan concentrations in all intraabdominal tissues. These differences were significant for the ileum (P=0.03) and jejunum (P=0.04).Conclusion Hyperthermia affected the pharmacokinetics of intraperitoneal melphalan by decreasing the AUC of peritoneal fluid melphalan without increasing the plasma AUC. It increased intraabdominal tissue concentrations.Olivier Glehen is supported by a grant from Fondation de France.     

Pharmacokinetics of Carboplatin in a patient with both testicular cancer and hemodialysis-requiring kidney failure

We report on a patient with advanced seminoma successfully treated with 4 cycles of carboplatin (80-100 mg/m2 per cycle) and etoposide (240-300 mg/m2) while being on hemodialysis 3 times weekly. Hemodialysis was performed on day 2 and day 3 of each chemotherapy cycle. Plasma platinum levels were determined at regular intervals at days 1, 2 and 3 of each cycle. The drug doses for cycle 2-4 were reduced due to grade 4 hematological toxicity during the preceding cycle. In spite of these drug reductions the AUC between 0-51 h remained unchanged for all cycles. Platinum was found in the plasma collected on day 1 of cycle 2-4 prior to start of the scheduled carboplatin infusion. The demonstrated pharmacokinetics of carboplatin (and probably also of etoposide) should be considered during chemotherapy of a testicular cancer patient on hemodialysis.