Three neonates being treated with various anticancer drugs were studied at two clinical centres in the UK. The first patient (001) was born full term, diagnosed with localised hepatoblastoma and treated with cisplatin monotherapy at 2 weeks of age and a body weight (BW) of 3.0 kg. The patient had a creatinine level of 22 µmol/L (within the normal range for this age ), liver function tests as measured by AST and ALT values of 29 and 9 U/L, respectively, and an albumin level of 22 g/L (all within normal ranges based on age ). An elevated bilirubin level of 199 µmol/L was observed (predominantly unconjugated bilirubin associated with neonatal jaundice) in addition to a highly elevated LDH level of 1067 U/L. An initial cisplatin dose of 5.4 mg (1.8 mg/kg) was administered as a 24-h intravenous infusion on course 1 of treatment, and blood samples were collected for quantification of cisplatin plasma concentrations. Prior to course 2 of treatment, the patient had a creatinine level of 21 µmol/L, AST and ALT values of 39 and 13 U/L, respectively, and an albumin level of 25 g/L (all within normal ranges based on age [10, 11]). The elevated bilirubin level measured on course 1 of treatment had reduced to 44 µmol/L prior to cisplatin administration on course 2. The dose of cisplatin was increased to 8.3 mg (2.7 mg/kg) on course 2 of treatment, based on the plasma concentrations observed on course 1 and how the patient tolerated treatment, with blood samples for pharmacokinetic analysis again collected.
The second patient (002) was born full term and diagnosed with Wilms’ tumour (stage 1 intermediate risk) on day 2 of life. They received weekly vincristine following a primary nephrectomy, according to the protocol recommended dose of 1.5 mg/m2 vincristine reduced by 50 % due to the very young age of the patient (3 weeks of age, BW 3.3 kg). A dose of 0.16 mg (0.05 mg/kg, 0.75 mg/m2) was administered as a short intravenous infusion, with blood samples collected for quantification of vincristine plasma concentrations. The patient had a creatinine level of 46 µmol/L (within the normal range for this age ) at initiation of chemotherapy, normal liver function tests (ALT 17 U/L, ALP 147 U/L), a bilirubin level of 13 µmol/L and an albumin level of 29 g/L (within normal ranges for patient age ). Albumin levels were seen to progressively increase to from 29 to 34 g/L during treatment.
The third patient (003) received carboplatin, etoposide and vincristine for the treatment of stage 4S neuroblastoma with MYCN amplification. The patient had been born 8 weeks premature at a gestational age of 32 weeks and was suffering from anuria when treated at age 8 weeks (gestational age 40 weeks), with a body weight of 2.5 kg. At the time of treatment, the patient had a creatinine level of 43 µmol/L (within the normal range for this age ), a relatively low albumin level (21 g/L), elevated ALT (97 U/L) and elevated bilirubin (54 µmol/L), consistent with acute liver injury secondary to tumour and hepatic artery ligation. Blood samples were collected for the analysis of carboplatin and etoposide plasma concentrations. Carboplatin was administered at a dose of 10 mg (4 mg/kg) as a 1-h intravenous infusion on days 1, 2 and 3 of treatment. Etoposide was administered as a 4-h intravenous infusion at a dose of 8 mg (3.2 mg/kg) on day 1 and at a dose of 12.5 mg (5 mg/kg) on days 3 and 4 of treatment, with vincristine administered as a short intravenous infusion at a dose of 0.28 mg (0.11 mg/kg) on day 4 only. The patient underwent continuous veno-venous haemofiltration (CVVH) before and after chemotherapy due to oligo-anuria.
Patient characteristics are provided alongside details of individual patient treatment in Table 1. Ethical approval was not required for this approach to treatment, providing information on drug levels as a clinical request by the treating centre to be used alongside tolerability data to guide the selection of dosing regimens over multiple courses of treatment. TDM in this setting was carried out at the request of the treating clinician.
Blood sampling and analysis
For patient 001, blood samples (1 mL) for pharmacokinetic analysis were obtained from a central line prior to cisplatin infusion, 6 h after the start of infusion, at 24 h (end of infusion) and at 8 h following the end of infusion. Plasma was separated from whole blood samples by centrifugation (1200 g, 4 °C, 10 min), and 0.5 mL was then removed and placed in an Amicon Centrifree micropartition unit with a 30,000 MW cut-off (Millipore, Edinburgh, UK). This sample was centrifuged (1500 g, 4 °C, 15 min) to obtain plasma ultrafiltrate for determination of free cisplatin levels. For patient 002, blood samples (2 mL) were collected at 30 min, 2 h, 6 h and 24 h following a short bolus infusion of vincristine, and plasma was immediately separated by centrifugation (1200 g, 4 °C, 10 min). For patient 003, blood samples were obtained before carboplatin infusion, 30 min after the start of infusion, at 1 h (end of infusion) and at 1 and 2 h after the end of infusion on days 1 and 2 of treatment. Plasma was separated from whole blood samples by centrifugation (1200 g, 4 °C, 10 min), and 0.5 mL was then removed for preparation of plasma ultrafiltrate as described above, for determination of free carboplatin levels. For analysis of etoposide levels in this patient, blood samples were collected at 2 h after the start of infusion, at 4 h (end infusion) and at 2 h after the end of infusion on day 1 of treatment, and plasma was immediately separated by centrifugation (1200 g, 4 °C, 10 min). All samples for quantification of drug levels were stored at −20 °C prior to analysis.
Samples were sent by overnight courier, on dry ice and in an insulated container, to the Northern Institute for Cancer Research, Newcastle University. Cisplatin and carboplatin pharmacokinetic analyses were carried out by flameless atomic absorption spectrophotometry (AAS) using a Perkin–Elmer AAnalyst 600 graphite furnace spectrometer (Perkin–Elmer Ltd, Beaconsfield, UK). Total and free (unbound) platinum levels were determined in plasma and plasma ultrafiltrate samples, respectively, as described previously [12, 13]. All samples were analysed in duplicate, and values expressed as the average of these measurements. Duplicate values were within 15 % of each other in all cases. Intra- and inter-assay coefficients of variation for a quality assurance sample had to be <10 % for an assay to be valid. The limit of detection for the AAS assay was 0.10 µg/mL. Quantification of vincristine levels in plasma samples was carried out using a validated liquid chromatography–mass spectrometry (LC/MS) assay, with a lower limit of quantification (LLOQ) of 0.50 ng/mL as previously described . Etoposide plasma concentrations were determined using an API 2000 LC/MS assay, with a standard curve of 0.20–10.0 µg/mL as previously described . Intra-assay coefficients of variation were <10 % in all cases.
Pharmacokinetic parameters for cisplatin, vincristine and etoposide were calculated by non-compartmental analysis using the WinNonlin software package. Carboplatin clearance (Cl) and AUC were determined by Bayesian analysis using a two-compartment model as described previously [13, 16].