Influence of pharmacogenetics on response and toxicity in breast cancer patients treated with doxorubicin and cyclophosphamide

BACKGROUND: Doxorubicin and cyclophosphamide (AC) therapy is an effective treatment for early-stage breast cancer. Doxorubicin is a substrate for ABCB1 and SLC22A16 transporters. Cyclophosphamide is a prodrug that requires oxidation to 4-hydroxy-cyclophosphamide, which yields a cytotoxic alkylating agent. The initial oxidation is catalysed by cytochrome P450 enzymes including CYP2B6, CYP2C9, CYP2C19 and CYP3A5. Polymorphic variants of the genes coding for these enzymes and transporters have been identified, which may influence the systemic pharmacology of the two drugs. It is not known whether this genetic variation has an impact on the efficacy or toxicity of AC therapy. METHODS: Germ line DNA samples from 230 patients with breast cancer on AC therapy were genotyped for the following SNPs: ABCB1 C1236T, G2677T/A and C3435T, SLC22A16 A146G, T312C, T755C and T1226C, CYP2B6*2, *8, *9, *3, *4 and *5, CYP2C9*2 and *3, CYP3A5*3 and CYP2C19*2. Clinical data on survival, toxicity, demographics and pathology were collated. RESULTS: A lower incidence of dose delay, indicative of less toxicity, was seen in carriers of the SLC22A16 A146G, T312C, T755C variants. In contrast, a higher incidence of dose delay was seen in carriers of the SLC22A16 1226C, CYP2B6*2 and CYP2B6*5 alleles. The ABCB1 2677A, CYP2B6*2, CYP 2B6*8, CYP 2B6*9, CYP 2B6*4 alleles were associated with a worse outcome. CONCLUSION: Variant alleles in the ABCB1, SLC22A16 and CYP2B6 genes are associated with response to AC therapy in the treatment of breast cancer

A phase I and pharmacokinetic study of indisulam in combination with carboplatin

Indisulam (E7070) is an anticancer agent that is currently being evaluated in phase II clinical studies. A significant reduction in glutathione synthetase and glutathione reductase transcripts by indisulam provided a molecular basis for its combination with platinum agents. Indisulam demonstrated high anti-tumour activity in various preclinical cancer models. The objectives of this study were (1) to determine the recommended dose of indisulam in combination with carboplatin in patients with solid tumours and (2) to evaluate the pharmacokinetics of the combination. Patients with solid tumours were treated with indisulam in combination with carboplatin. Indisulam (350, 500, or 600 mg m−2) was given as a 1-hour intravenous infusion on day 1 and carboplatin (5 or 6 mg min ml−1) as an intravenous infusion over 30 min on day 2 of a three-weekly cycle. Sixteen patients received study treatment and were eligible. Thrombocytopenia was the major dose limiting toxicity followed by neutropenia. Both drugs contributed to the myelosuppressive effect of the combination. Indisulam 500 mg m−2 in combination with carboplatin 6 mg min ml−1 was identified not to cause dose limiting toxicity, but a delay of re-treatment by 1 week was required regularly to allow recovery from myelosuppression. The recommended dose and schedule for an envisaged phase II study in patients with non-small cell lung cancer is indisulam 500 mg m−2 in combination with carboplatin 6 mg min ml−1 repeated four-weekly. Patients who do not experience severe thrombocytopenia at cycle 1 will be permitted to receive an escalated dose of indisulam of 600 mg m−2 from cycle 2 onwards

Carboplatin dosing in overweight and obese patients with normal renal function, does weight matter?

PURPOSE: The purpose of this study was to determine the potential utility of alternative weight descriptors in the Cockcroft-Gault equation to more accurately predict carboplatin clearance in underweight, normal weight, overweight and obese patients. METHODS: Clearance values obtained from individual fits using NONMEM were compared to predicted carboplatin clearances calculated using the modified Calvert formula in which creatinine clearance was calculated with the Cockcroft-Gault equation using diverse weight descriptors. RESULTS: This study indicated that lean body mass was the best weight descriptor in underweight and normal weight patients, while adjusted ideal body weight was the best weight descriptor in overweight and obese patients. However, a flat dose based on the population carboplatin clearance performed better in all weight categories than the use of the Cockcroft-Gault equation with diverse weight descriptors. CONCLUSION: These results suggest that in overweight and obese patients, with a normal renal function, a flat carboplatin dose should be administered, based on the population carboplatin clearance (8.38 l/h = 140 mL/min). Thus, in case an AUC of 5 mg min/mL is desired, the appropriate dose for carboplatin would be 5 x 140 = 700 m

Relations between polymorphisms in drug-metabolising enzymes and toxicity of chemotherapy with cyclophosphamide, thiotepa and carboplatin

PURPOSE: High-dose chemotherapy with cyclophosphamide, thiotepa and carboplatin (CTC) has been developed as a possible curative treatment modality in several solid tumours. However, a large interindividual variability in toxicity is encountered in high-dose chemotherapy. A priori identification of patients at risk for toxicity could be an attractive prospect. Genotyping of genes encoding drug-metabolising enzymes might provide such a tool. EXPERIMENTAL DESIGN: We assessed 16 selected polymorphisms in nine genes (CYP2B6, CYP2C9, CYP2C19, CYP3A4, CYP3A5, GSTA1, GSTP1, ALDH1A1 and ALDH3A1) of putative relevance in CTC metabolism using polymerase chain reaction and DNA sequencing in 113 patients who were treated with high-dose chemotherapy regimens based on CTC. RESULTS: Patients heterozygous for the ALDH3A1*2 allele (allelic frequency 21.2%) had an increased risk of haemorrhagic cystitis when compared with patients with wild-type alleles [5/38 vs. 1/70; odds ratio (OR): 11.95, 95% confidence interval (CI): 1.18-120.56; P=0.04]. Furthermore, patients heterozygous for the ALDH1A1*2 allele (allelic frequency 5.8%) had an increased risk of liver toxicity when compared with patients with wild-type alleles (6/13 vs. 19/99; OR: 5.13, 95% CI: 1.30-20.30; P=0.02). No other relations reached significance. CONCLUSION: Patients heterozygous for the ALDH3A1*2 and ALDH1A1*2 allele have an increased risk of haemorrhagic cystitis and liver toxicity, respectively, compared with patients with wild-type alleles when treated with a high-dose chemotherapy combination of CTC. Pharmacogenetic approaches can identify patients who are at risk of experiencing toxic side effects in high-dose chemotherap

Altered cyclophosphamide and thiotepa pharmacokinetics in a patient with moderate renal insufficiency

PURPOSE: We report a patient with renal insufficiency (creatinine clearance, CL(cr) = 38 mL/min) who received high-dose chemotherapy with cyclophosphamide (1,500 mg/m(2) day(-1)), thiotepa (120 mg/m(2) day(-1)) and carboplatin (AUC = 5 mg min/mL day(-1)) for four consecutive days. METHODS: Blood samples were collected on day 1 and 3 and plasma levels of cyclophosphamide, its active metabolite 4-hydroxycyclophosphamide, thiotepa, its main metabolite tepa and carboplatin were determined. RESULTS: Pharmacokinetic analyses indicated that the elimination of cyclophosphamide, thiotepa, carboplatin, but especially tepa was strongly reduced in this patient, resulting in increased exposures to these compounds of 67, 43, 30 and 157%, respectively, compared to a reference population (n = 24) receiving similar doses. Exposure to 4-hydroxycyclophosphamide increased 11%. CONCLUSION: These results suggest that it may not be necessary to alter the dose of cyclophosphamide in patients with moderate renal impairment. However, because high exposures to thiotepa and tepa have been correlated with increased toxicity, caution should be applied when administering thiotepa to patients with renal insufficienc