Tamoxifen pharmacokinetics and pharmacodynamics in older patients with non-metastatic breast cancer

BACKGROUND

We aimed to study the pharmacokinetics and -dynamics of tamoxifen in older women with non-metastatic breast cancer.

METHODS

Data for this analysis were derived from the CYPTAM study (NTR1509) database. Patients were stratified by age (age groups < 65 and 65 and older). Steady-state trough concentrations were measured of tamoxifen, N-desmethyltamoxifen, 4-hydroxy-tamoxifen, and endoxifen. CYP2D6 and CYP3A4 phenotypes were assessed for all patients by genotyping. Multiple linear regression models were used to analyze tamoxifen and endoxifen variability. Outcome data included recurrence-free survival at time of tamoxifen discontinuation (RFSt) and overall survival (OS).

RESULTS

668 patients were included, 141 (21%) were 65 and older. Demographics and treatment duration were similar across age groups. Older patients had significantly higher concentrations of tamoxifen 129.4 ng/ml (SD 53.7) versus 112.2 ng/ml (SD 42.0) and endoxifen 12.1 ng/ml (SD 6.6) versus 10.7 ng/ml (SD 5.7, p all < 0.05), independently of CYP2D6 and CYP3A4 gene polymorphisms. Age independently explained 5% of the variability of tamoxifen (b = 0.95, p < 0.001, R² = 0.051) and 0.1% of the variability in endoxifen concentrations (b = 0.45, p = 0.12, R² = 0.007). Older patients had worse RFSt (5.8 versus 7.3 years, p = 0.01) and worse OS (7.8 years versus 8.7 years, p = 0.01). This was not related to differences in endoxifen concentration (HR 1.0, 95% CI 0.96-1.04, p = 0.84) or CYP polymorphisms.

CONCLUSION

Serum concentrations of tamoxifen and its demethylated metabolites are higher in older patients, independent of CYP2D6 or CYP3A4 gene polymorphisms. A higher bioavailability of tamoxifen in older patients may explain the observed differences. However, clinical relevance of these findings is limited and should not lead to a different tamoxifen dose in older patients.

Real-World Metastatic Renal Cell Carcinoma Treatment Patterns and Clinical Outcomes in The Netherlands

The number of treatment options for patients with metastatic renal cell carcinoma (mRCC) has significantly grown in the last 15 years. Although randomized controlled trials are fundamental in investigating mRCC treatment efficacy, their external validity can be limited. Therefore, the efficacy of the different treatment options should also be evaluated in clinical practice. We performed a chart review of electronic health records using text mining software to study the current treatment patterns and outcomes. mRCC patients from two large hospitals in the Netherlands, starting treatment between January 2015 and May 2020, were included. Data were collected from electronic health records using a validated text mining tool. Primary endpoints were progression-free survival (PFS) and overall survival (OS). Statistical analyses were performed using the Kaplan-Meier method. Most frequent first-line treatments were pazopanib (n = 70), sunitinib (n = 34), and nivolumab with ipilimumab (n = 28). The overall median PFS values for first-line treatment were 15.7 months (95% confidence interval [95%CI], 8.8-20.7), 16.3 months (95%CI, 9.3-not estimable [NE]) for pazopanib, and 6.9 months (95% CI, 4.4-NE) for sunitinib. The overall median OS values were 33.4 months (95%CI, 28.1-50.9 months), 39.3 months (95%CI, 29.5-NE) for pazopanib, and 28.1 months (95%CI, 7.0-NE) for sunitinib. For nivolumab with ipilimumab, median PFS and median OS were not reached. Of the patients who finished first- and second-line treatments, 64 and 62% received follow-up treatments, respectively. With most patients starting on pazopanib and sunitinib, these real-world treatment outcomes were most likely better than in pivotal trials, which may be due to extensive follow-up treatments.

Safety and pharmacokinetic analysis of UGT1A1 genotype-guided dosing of irinotecan

3574

Background: Irinotecan is commonly used in the treatment of advanced colorectal and pancreatic cancer. The polymorphisms UGT1A1*28 (7 TA repeats) and UGT1A1*93 (SNP -3156G > A) are significantly associated with increased systemic exposure of irinotecan’s active metabolite SN-38 and subsequently severe irinotecan-associated adverse-events (AEs) including (febrile) neutropenia and diarrhea. Severe AEs may lead to hospitalization, loss of quality of life, treatment delay and/or treatment discontinuation. Nonetheless, prospective genetic screening is not yet routinely performed. The aim of this study was to determine the safety and pharmacokinetics of UGT1A1 genotype-guided dosing of irinotecan in UGT1A1 poor metabolizers (PMs), i.e. UGT1A1 *28/*28 and/or UGT1A1*93/*93 individuals, in order to reduce the incidence of severe irinotecan-associated AEs. Methods: A prospective, multi-center, non-randomized study was conducted in patients intended to be treated with irinotecan at a dose of ≥ 180 mg/m2 or 450-600 mg flat dose. All patients were pre-therapeutically genotyped for UGT1A1*28 and UGT1A1*93. In UGT1A1 PMs, an initial 30% dose reduction in the first cycle was applied followed by further individual dose titration based on neutrophil count and clinical tolerability. The primary endpoint was the incidence of febrile neutropenia in the first 2 cycles of irinotecan treatment. UGT1A1 PMs were compared to 1] historical control patients, i.e. homozygous polymorphic patients treated with full dose therapy identified from systematic literature review and to 2] UGT1A1 non-PMs treated with standard dose therapy. In addition, systemic SN-38 exposure (AUC0-500h) of reduced dosing in the UGT1A1 PM cohort was compared to a standard dosed irinotecan patient cohort [doi: 10.1200/JCO.2000.18.1.195] by an independent T-test. Results: A total of 349 patients were pre-therapeutically genotyped and included for analysis. Thirty-one (8.9%) patients were UGT1A1 PM, in whom an initial median 30% dose reduction was applied. The incidence of febrile neutropenia in this group was 6.5% compared to 24% in historical controls (n = 50) (p = 0.042) and comparable with the incidence (4.1%; p = 0.632) in UGT1A1 non-PMs treated with full dose therapy. The systemic exposure of SN-38 of reduced dosing in UGT1A1 PMs (n = 17) was comparable to the systemic exposure of the standard dosed irinotecan patient cohort (n = 46) with a relative difference of +24% (p = 0.054) with a geometric mean (CV) of SN-38 AUC0-500h of 391 (43.7%) versus 298 (75.3%) ng*h/mL, respectively. Conclusions: UGT1A1 genotype-guided dosing significantly reduces the incidence of febrile neutropenia in UGT1A1 PM patients treated with irinotecan. In addition, systemic drug exposure remained adequate, despite the 30% dose reduction. Therefore, UGT1A1 genotype-guided dosing of irinotecan should be considered standard of care in order to improve the individual patient safety. Clinical trial information: Trial NL6270 (NTR6612).

3D printed furosemide and sildenafil tablets: Innovative production and quality control

Three-dimensional (3D) printing of pharmaceuticals has the potential to revolutionise personalised medicine but is as yet largely unexplored. A proof-of-concept study of a novel heated, piston-driven semi-solid extrusion 3D printer was performed by producing furosemide and sildenafil tablets for paediatric patients. The average weight of the tablets was 141.1 mg (RSD 1.26%). The acceptance values of the content uniformity were 4.2-10.6 (concentration RSD 0.41-0.63%), 4.8-8.9 (concentration RSD 0.76-0.97%) and 6.6-9.2 (concentration RSD 0.94-1.44%) for furosemide 2 mg, 10 mg and sildenafil 4 mg, respectively. The dissolution rate limiting step was the dissolving and eroding of the tablet matrix and showed an immediate release. The tablets complied to the requirements of the European Pharmacopoeia (EP) for uniformity of mass (EP 2.9.5), content uniformity (EP 2.9.40) and conventional release (EP 2.9.3). While they complied, not all of these quality tests for tablets might be suitable for 3D printed tablets due to the layering of the tablets and the small batch production. To assess adequate layer adhesion adjusted friability (EP 2.9.7) and resistance to crushing (EP 2.9.8) tests are proposed.

Effect of CYP2C19 genotypes on tamoxifen metabolism and early-breast cancer relapse

CYP2C19*2 and CYP2C19*17 might influence tamoxifen metabolism and clinical outcome. Our aim was to investigate the effect of CYP2C19 genotypes on tamoxifen concentrations and metabolic ratios (MRs) and breast cancer recurrence in a large cohort of Caucasian women. Genetic variants (CYP2D6 and CYP2C19 genotypes), tamoxifen and metabolites concentrations, baseline characteristics, and breast cancer recurrence from the CYPTAM study (NTR1509) were used. CYP2C19*2 and CYP2C19*17 genotypes were evaluated as alleles and as groups based on CYP2D6 genotypes (high, intermediate and low activity). Log-rank test and Kaplan–Meier analysis were used to evaluate differences in recurrence defined as relapse-free survival (RFS). Classification tree analyses (CTAs) were conducted to assess the levels of interactions per polymorphism (CYP2D6 and CYP2C19 genotypes) on endoxifen concentrations. No differences in mean concentrations and MRs were observed when comparing CYP2C19 genotypes (CYP2C19*1/*1; CYP2C19*1/*2; CYP2C19*2/*2; CYP2C19*1/*17; CYP2C19*17/*17; CYP2C19*2/*17). Only significant differences (p value < 0.05) in mean concentrations and MRs were observed when comparing tamoxifen activity groups (high, intermediate and low activity). A log-rank test did not find an association across CYP2C19 genotypes (p value 0.898). CTAs showed a significant relationship between CYP2D6 and endoxifen (p value < 0.0001), but no association with CYP2C19 genotypes was found. CYP2C19 polymorphisms do not have a significant impact on tamoxifen metabolism or breast cancer relapse.

Identification of pharmacogenetic biomarkers for efficacy of cytoreductive surgery plus hyperthermic intraperitoneal mitomycin C in patients with colorectal peritoneal metastases

INTRODUCTION

Mitomycin C (MMC) is commonly used in patients with colorectal peritoneal metastases (CPM) treated with cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (CRS + HIPEC). MMC requires metabolic activation prior to exert its cytotoxic effect of which the main activating enzymes are NQO1 and POR. However, not all patients are able to activate MMC for example due to polymorphisms in the genes encoding these enzymes. The aim of this study was to investigate the association of NQO1∗2, NQO1∗3, and POR∗28 with the efficacy of CRS + HIPEC with MMC in patients with CPM.

METHOD

A retrospective follow-up design was used to study genetic association in patients with histologically proven CPM treated with CRS + HIPEC with MMC with respect to peritoneal recurrence rate after 3 months (primary endpoint), after 6 months, disease-free survival and overall survival. Genetic polymorphisms NQO1∗2, NQO1∗3, and POR∗28 were tested for association.

RESULTS

A total of 253 patients were included. In NQO1∗3 carriers the peritoneal recurrence rate 3 and 6 months after HIPEC was significantly higher than in wild type patients, respectively 30.0% vs 3.8% (p = 0.009) and 40.0% vs 12.1% (p = 0.031). In line with these results, NQO1∗3 was associated with a shorter disease-free survival (HR 2.04, 95% CI [1.03-4.03]). There was no significant association with overall survival (HR 1.42, 95% CI [0.66-3.07]).

CONCLUSION

Carriership of the NQO1∗3 allele is associated with worse peritoneal recurrence rate and disease-free survival. These results suggest that individualization of patients treated with CRS + HIPEC based upon pharmacogenetics may be beneficial.

Population pharmacokinetics of treosulfan in paediatric patients undergoing hematopoietic stem cell transplantation

Aims

Treosulfan is an alkylating agent increasingly used prior to haematopoietic stem cell transplantation. The aim of this study was to develop a population pharmacokinetic (PK) model of treosulfan in paediatric haematopoietic stem cell transplantation recipients and to explore the effect of potential covariates on treosulfan PK. Also, a limited sampling model (LSM) will be developed to accurately predict treosulfan exposure suitable for a therapeutic drug monitoring setting.

Methods

In this multicentre study, 91 patients, receiving a total dose of 30, 36 or 42 g/m² treosulfan, administered over 3 consecutive days, were enrolled. A population PK model was developed and demographic factors, as well as laboratory parameters, were included as potential covariates. In addition, a LSM was developed using data from 28 patients.

Results

A 2‐compartment model with first order elimination best described the data. Bodyweight with allometric scaling and maturation function were identified as significant predictors of treosulfan clearance. Treosulfan clearance reaches 90% of adult values at 4 postnatal years. A model‐based dosing table is presented to target an exposure of 1650 mg*h/L (population median) for different weight and age groups. Samples taken at 1.5, 4 and 7 hours after start of infusion resulted in the best limited sampling strategy.

Conclusions

This study provides a treosulfan population PK model in children and captures the developmental changes in clearance. A 3‐point LSM allows for accurate and precise estimation of treosulfan exposure.

Pharmacokinetics and safety of panitumumab in a patient with chronic kidney disease

Purpose

Data on panitumumab dosing in cancer patients with renal insufficiency are lacking. Here, we report a 63-year-old metastatic colorectal cancer patient with chronic kidney injury with a glomerular filtration rate of approximately 11 mL/min.

Methods

Pharmacokinetic parameters, including dose-normalized area under the curve, clearance and elimination half-life (T_1/2) after the 11th and 12th infusions were estimated using trapezoidal non-compartmental methods. Data were compared to previous reported pharmacokinetic data from studies in patients with normal renal function.

Results

The results show that the pharmacokinetic data in this patient with kidney failure are comparable to those in patients with adequate renal function. Moreover the treatment was well tolerated in this patient.

Conclusion

This study suggests that panitumumab can be safely used in cancer patients with renal impairment without dose adjustment.

Effect of CYP3A4*22, CYP3A5*3, and CYP3A combined genotypes on tamoxifen metabolism

Background

Tamoxifen is one of the cornerstones of endocrine therapy for breast cancer. Recently, the decreased activity CYP3A4*22 allele and the loss of function CYP3A5*3 allele have been described as potential factors that could help to explain the inter-patient variability in tamoxifen metabolism. The aim of this study is to investigate the effect of CYP3A4*22, CYP3A5*3, and CYP3A combined genotypes on tamoxifen metabolism.

Methods

DNA from 667 women enrolled in the CYPTAM study (NTR1509) was genotyped (CYP2D6, CYP3A4*22, and CYP3A5*3). Tamoxifen and metabolite concentrations were measured in serum, and metabolic ratios were calculated. The effect of the CYP3A4*22, CYP3A5*3, and CYP3A combined genotypes in addition to the CYP2D6 genotypes was examined by multiple linear regression analysis.

Results

CYP3A4*22 carriers reached significant higher concentrations of tamoxifen, N-desmethyl-tamoxifen, and 4-hydroxy-tamoxifen compared to non-carriers, whereas a tendency toward increased endoxifen levels was observed (p = 0.088). The metabolic ratio tamoxifen/N-desmethyl-tamoxifen was significantly higher in CYP3A4*22 individuals (0.59 vs. 0.52, p < 0.001). At the same time, CYP3A4*22 genotype contributed to improving the inter-variability [R² of the (log-transformed) metabolic ratio tamoxifen/N-desmethyl-tamoxifen improved from 21.8 to 23.9%, p < 0.001]. CYP3A5*3 marginally improved the explained variability of the (log transformed) metabolic ratio 4-hydroxy-tamoxifen/endoxifen (from 44.9 to 46.2%, p < 0.038).

Conclusion

Our data demonstrate that CYP3A genotype has a minor effect to explaining the variability between patients in tamoxifen metabolism and has no added value in addition to CYP2D6 genotype.

Electronic supplementary material

The online version of this article (10.1007/s00228-017-2323-2) contains supplementary material, which is available to authorized users.

Population Modeling Integrating Pharmacokinetics, Pharmacodynamics, Pharmacogenetics, and Clinical Outcome in Patients With Sunitinib-Treated Cancer

The tyrosine kinase inhibitor sunitinib is used as first‐line therapy in patients with metastasized renal cell carcinoma (mRCC), given in fixed‐dose regimens despite its high variability in pharmacokinetics (PKs). Interindividual variability of drug exposure may be responsible for differences in response. Therefore, dosing strategies based on pharmacokinetic/pharmacodynamic (PK/PD) models may be useful to optimize treatment. Plasma concentrations of sunitinib, its active metabolite SU12662, and the soluble vascular endothelial growth factor receptors sVEGFR‐2 and sVEGFR‐3, were measured in 26 patients with mRCC within the EuroTARGET project and 21 patients with metastasized colorectal cancer (mCRC) from the C‐II‐005 study. Based on these observations, PK/PD models with potential influence of genetic predictors were developed and linked to time‐to‐event (TTE) models. Baseline sVEGFR‐2 levels were associated with clinical outcome in patients with mRCC, whereas active drug PKs seemed to be more predictive in patients with mCRC. The models provide the basis of PK/PD‐guided strategies for the individualization of anti‐angiogenic therapies.

Everolimus pharmacokinetics and its exposure-toxicity relationship in patients with thyroid cancer

Background

Everolimus is a mTOR inhibitor used for the treatment of different solid malignancies. Many patients treated with the registered fixed 10 mg dose once daily are in need of dose interruptions, reductions or treatment discontinuation due to severe adverse events. This study determined the correlation between systemic everolimus exposure and toxicity. Additionally, the effect of different covariates on everolimus pharmacokinetics (PK) was explored.

Methods

Forty-two patients with advanced thyroid carcinoma were treated with 10 mg everolimus once daily. Serial pharmacokinetic sampling was performed on days 1 and 15. Subsequently, a population PK model was developed using NONMEM to estimate individual PK values used for analysis of an exposure–toxicity relationship. Furthermore, this model was used to investigate the influence of patient characteristics and genetic polymorphisms in genes coding for enzymes relevant in everolimus PK.

Results

Patients who required a dose reduction (n = 18) due to toxicity at any time during treatment had significant higher everolimus exposures [mean AUC_0–24 (SD) 600 (274) vs. 395 (129) µg h/L, P = 0.008] than patients without a dose reduction (n = 22). A significant association between everolimus exposure and stomatitis was found in the four-level ordered logistic regression analysis (P = 0.047). The presence of at least one TTT haplotype in the ABCB1 gene was associated with a 21 % decrease in everolimus exposure.

Conclusion

The current study showed that dose reductions and everolimus-induced stomatitis were strongly associated with systemic everolimus drug exposure in patients with cancer. Our findings confirm observations from another study in patients with cancer and show us that everolimus is a good candidate for individualized dosing in patients with cancer.

ClinicalTrial.gov number

NCT01118065.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-016-3050-6) contains supplementary material, which is available to authorized users.

Abstract P3-07-54: Insulin-like growth factor 1 receptor expression and polymorphism are associated with response to neoadjuvant chemotherapy in breast cancer patients: Results from the NEOZOTAC trial (BOOG 2010-01)

Background

The insulin-like growth factor 1 (IGF-1) pathway is involved in cell growth, proliferation and cell cycle progression and associated with tumor genesis and therapy resistance. This study aims to elucidate whether variation in the IGF-1 pathway is predictive for pathologic response in early breast cancer (BC) patients taking part in the phase III NEOZOTAC trial, randomizing between 6 cycles of neoadjuvant TAC chemotherapy with or without zoledronic acid.

Method

Formalin-fixed paraffin-embedded (FFPE) tissue samples of pre-chemotherapy biopsies and operation specimens were collected for analysis of IGF-1 receptor (IGF-1R) expression using IHC (n=216) and for analysis of 8 candidate SNPs in genes of the IGF-1 pathway (n=184) using OpenArray® RealTime PCR. Optionally, blood samples were collected immediately before chemotherapy for determination of glucose, insulin, IGF-1, IGF-2 and IGF-BP3. Associations with patient and tumor characteristics and chemotherapy response according to Miller and Payne (MP) pathologic response were performed using chi square and logistic regression analyses.

Results

High IGF-1R expression was associated with estrogen receptor expression (P=0.001). During chemotherapy, a significant number of the tumors (47.2%) showed a decrease in IGF-1R expression, while in a small number of the tumors an upregulation was seen (15.1%). IGF-1R expression before treatment was not associated with pathological response, however absence of IGF-1R expression after treatment was associated with a better response in multivariate analyses (P=0.012) and patients with a decrease in expression during treatment showed a better response to chemotherapy as well (P=0.008). Moreover, the variant T allele of 3129G&gt;T in IGF-1R (rs2016347) was associated with a better pathological response in multivariate analyses (P=0.032). In addition, high glucose and insulin levels were associated with positive lymph node status before chemotherapy in multivariate analysis (P=0.019) and (P=0.031), respectively.

Conclusion

Neoadjuvant chemotherapy induced changes in the IGF-1R expression in most of the tumors. Absence or diminished expression of IGF-1R after treatment was associated with a better pathological response. Additionally, we found a SNP (rs2016347) in IGF-1R as a potential predictive marker for chemotherapy efficacy in BC patients treated with TAC. These findings may help to select patients who might benefit from (co-)treatment with an IGF-1 pathway inhibitor.

Citation Format: de Groot S, Charehbili A, van Laarhoven HWM, Mooyaart AL, Dekker-Ensink NG, van de Ven S, Janssen LGM, Swen JJ, Smit VTHBM, Heijns JB, Kessels LW, van der Straaten RJHM, Bhringer S, Gelderblom AJ, van der Hoeven JJM, Guchelaar HJ, Pijl H, Kroep JR. Insulin-like growth factor 1 receptor expression and polymorphism are associated with response to neoadjuvant chemotherapy in breast cancer patients: Results from the NEOZOTAC trial (BOOG 2010-01). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-54.

Exploratory analysis of candidate germline gene polymorphisms in breast cancer patients treated with neoadjuvant anthracycline-containing chemotherapy and associations with febrile neutropenia

AIM

SNPs may be associated with (side) effects of chemotherapy and may be useful as biomarkers to predict febrile neutropenia.

PATIENTS & METHODS

187 DNA samples extracted from formalin-fixed paraffin-embedded tissue from patients with stage II/III HER2-negative breast cancer were genotyped.

RESULTS

Candidate SNPs were selected and explored for association with febrile neutropenia and/or pathological complete response. TT genotype of 388 C>T in FGFR4 (rs351855) had a tendency toward higher incidence of febrile neutropenia during neoadjuvant chemotherapy, compared with the CT (p = 0.383) genotype and compared with the CC genotype (p = 0.068).

CONCLUSION

The TT genotype of 388 C>T FGFR4 may be related to incidence of febrile neutropenia during neoadjuvant TAC (docetaxel, doxorubicin, cyclophosphamide) chemotherapy and is possibly useful as a patient-related risk factor when assessing febrile neutropenia risk. Original submitted 23 January 2015; Revision submitted 26 May 2015.

Short-term variation in plasma mitotane levels confirms the importance of trough level monitoring

OBJECTIVE

Mitotane is the drug of choice in patients with adrenocortical carcinoma. The anti-neoplastic effect is correlated with mitotane plasma levels, which render it crucial to reach and maintain the concentration above 14 mg/l. However, mitotane pharmacokinetics is poorly understood. The aim of this study was to investigate the variation in plasma mitotane levels during the day and the influence of a single morning dose.

DESIGN

A prospective case-control study was conducted to investigate the variation in plasma mitotane levels.

METHODS

Patients who had been treated for at least 24 weeks and had reached the therapeutic plasma level (14 mg/l) at least once were eligible. In the first group, mitotane levels were determined hourly for the duration of 8 h after administration of a single morning dose. In the second group, mitotane levels were assessed similarly without administration of a morning dose.

RESULTS

Ten patients were included in this study, and three patients participated in both groups. Median plasma level at baseline was 16.2 mg/l (range 11.3-23.3 mg/l) in the first group (n=7) and 17.0 mg/l (13.7-23.8) in the second group (n=6). Plasma levels displayed a median increase compared with baseline of 24% (range 6-42%) at t=4 after morning dose and a change of 13% (range -14 to 33%) at t=4 without morning dose (P=0.02).

CONCLUSION

A substantial increase in mitotane plasma levels was observed in steady-state patients within a period of 8 h after morning dosing. Without morning dose, mitotane curves showed a variable profile throughout the day. This implies that random sampling could yield incidentally high levels. For this reason, we recommend early-morning trough sampling as standard management in monitoring mitotane treatment.

Effect of PK-guided tamoxifen dose escalation on endoxifen serum concentrations in CYP2D6 intermediate and poor metabolizers

595

Background: Breast cancer patients with absent or reduced CYP2D6 activity may benefit less from tamoxifen treatment because of impaired biotransformation to the active metabolite endoxifen. We investigated whether a temporary one-step dose escalation of tamoxifen in CYP2D6 poor (PM) and intermediate metabolizers (IM) could increase endoxifen serum concentration to a similar level observed in CYP2D6 extensive metabolizers (EM) without increasing toxicity. Methods: From a prospective study population of early breast cancer patients using tamoxifen, 12 CYP2D6 poor and 12 intermediate metabolizers were selected and included in a one-step tamoxifen dose escalation study during two months. The escalation dose (120 mg maximum) was calculated by multiplying the individual’s endoxifen level divided by the median endoxifen concentration (33.7 nM) observed in CYP2D6 extensive metabolizers by 20 mg. Toxicity was assessed and all patients returned to the standard dose of 20 mg after two months. Results: Tamoxifen dose escalation in CYP2D6 poor and intermediate metabolizers significantly increased endoxifen concentrations (PMs: from 8.0 nM to 27.3 nM, p<0.001; IMs: from 17.8 nM to 30.3 nM, p=0.002) without increasing side effects. In intermediate but not in poor metabolizers dose escalation increased endoxifen to levels comparable with those observed in extensive metabolizers using tamoxifen 20 mg once daily (33.7 nM). Conclusions: CYP2D6 genotype and endoxifen guided tamoxifen dose escalation increased endoxifen concentrations without increasing short term side effects. Whether such tamoxifen dose escalation is effective and safe in view of long term toxic effects is uncertain and needs to be explored. Clinical trial information: NTR1509.

Safety and efficacy of the addition of simvastatin to cetuximab in KRAS mutant metastatic colorectal cancer patients

e14586

Background: Epithelial growth factor receptor (EGFR) inhibitors are not effective in KRAS mutant colorectal tumors. In these tumors the k-ras protein is activated by post-translational modification by binding farnesyl (C15) and geranylgeranyl (C17) moieties. Both are products of the mevalonate pathway, as is cholesterol. Statins (HMG-CoA-reductase inhibitors) not only inhibit synthesis of cholesterol, but also of C15 and C17 and thus may reduce post-translational activation of ras proteins. Therefore, statins may inhibit the expression of the mutant KRAS phenotype and normalize the phenotype into KRAS wild type. In a phase II study we investigated whether simvastatin treatment renders KRAS mutant colorectal tumors sensitive to cetuximab. Methods: Major eligibility criteria were metastatic colorectal cancer failing 5-FU, oxaliplatin and irinotecan containing regimens, with a mutation in codon 12, 13 or 61 of KRAS gene in a tumor sample. Patients were treated with simvastatin 80mg once daily and cetuximab 250mg/m2 weekly (after a starting dose of 400mg/m2). Primary objective was to investigate the percentage of patients free from progression and alive 12.5 weeks after the first administration of cetuximab, similar to the results of the KRAS wild type population of the phase III study. This phase II study was performed in a Simon two stage design, performing an interim analysis after enrolment of 15 patients. If at least 6 of these patients (i.e. 40%) were to be alive and free from progression at 12.5 weeks after the start of cetuximab, another 31 patients would be included during stage II. Results: Fifteen evaluable patients were enrolled at 3 study sites. Four patients (i.e. 27%) were free from progression at time of the primary endpoint. Three patients experienced serious adverse events; an allergic reaction during cetuximab infusion, rhabdomyolysis and intracranial haemorrhage due to cerebral metastases. Conclusions: Though 4 patients experienced stable disease at 12.5 weeks, the predefined efficacy boundary was not met in order to continue enrolment to stage II. Simvastatin 80mg once daily does not induce sensitivity to cetuximab in colorectal cancer patients with a mutation in the KRAS gene. Clinical trial information: NCT01190462.

Safety and efficacy of the addition of simvastatin to panitumumab in KRAS mutant metastatic colorectal cancer patients

e14558

Background: Epithelial growth factor receptor (EGFR) inhibitors are not effective in KRAS mutant colorectal tumors. In these tumors the k-ras protein is activated by post-translational modification by binding farnesyl (C15) and geranylgeranyl (C17) moieties. Both are products of the mevalonate pathway, as is cholesterol. Statins (HMG-CoA-reductase inhibitors) not only inhibit synthesis of cholesterol, but also of C15 and C17 and thus may relevantly inhibit post-translational activation of ras proteins. Therefore, statins may inhibit the expression of the mutant KRAS phenotype and normalize the phenotype into KRAS wild type. In a phase II study we investigated whether simvastatin treatment renders KRAS mutant colorectal tumors sensitive to panitumumab. Methods: Major eligibility criteria were advanced or metastatic colorectal cancer failing prior 5FU, oxaliplatin and irinotecan containing regimens, with a mutation in codon 12, 13 or 61 of KRAS gene on tumor sample. Patients were treated with simvastatin 80mg once daily and panitumumab 6mg/kg every 2 weeks. Primary objective was to investigate the percentage of patients free from progression and alive 11 weeks after the first administration of panitumumab. This phase II study was performed in a Simon two stage design, performing an interim analysis after the enrolment of 15 patients. When at least 6 of these patients (i.e. 40%) were to be alive and free from progression free at 11 weeks after the first administration of panitumumab (similar to the results of the KRAS wild type population of the phase III study), another 31 patients would be included during stage 2. Results: Fifteen evaluable patients were enrolled by 4 study sites. Only one patient was free from progression 11 weeks after start of panitumumab treatment (6.7%). Mean progression free survival was 9.1 weeks (range 5-17 weeks). Most frequent reported side effect was skin toxicity (40%), one patient experienced myositis grade 3. Conclusions: Simvastatin 80mg once daily was not able to inhibit the KRAS mutant phenotype sufficiently to reach sensitivity to panitumumab in colorectal cancer patients with a mutation in the KRAS gene. Clinical trial information: NCT01110785.

CYP3A4 phenotyping with midazolam to predict sunitinib exposure

2592

Background: Patients treated with sunitinib show high inter-patient variability in drug exposure (40-60%), which is largely unexplained. Since sunitinib is metabolized by CYP3A4, variability in the activity of this enzyme may explain a considerable proportion of the observed variability. We therefore prospectively studied the relationship between CYP3A4 activity and systemic exposure to sunitinib. Methods: In fifteen patients treated with sunitinib in a four weeks “on” – two weeks “off” regimen the pharmacokinetics of sunitinib and its active metabolite SU12662 were assessed. To determine sunitinib+SU12662 steady-state exposure, samples were collected over 24hrs after at least 14 days of sunitinib therapy. To assess CYP3A4 activity, midazolam 7.5mg orally was administered on the final day of the two weeks “off”. Plasma concentrations were measured over a period of 7hrs to determine midazolam exposure. Exposures (AUC) were calculated using a trapezoidal approach (Phoenix WinNonlin v6.3). The relationship between CYP3A4 activity (midazolam exposure) and sunitinib+SU12662 exposure was determined by linear regression analysis. The percentage of variability in sunitinib+SU12662 exposure that could be explained by CYP3A4 activity was calculated by Pearson’s correlation. In addition, the correlation between sunitinib+SU12662 Ctrough levels and sunitinib+SU12662 exposure was assessed. Results: A strong correlation between midazolam exposure (AUC0-7hr) and steady-state sunitinib+SU12662 exposure (AUC0-24hr) was found (p= 0.002); CYP3A4 activity explained 55% of the observed inter-patient PK variability of sunitinib+SU12662. Furthermore sunitinib+SU12662 Ctrough levels were highly predictive (96%) for overall sunitinib+SU12662 exposure (AUC0-24hr). Conclusions: Midazolam as a phenotyping probe could be useful before start of sunitinib therapy to identify patients at risk for under- respectively overtreatment at a standard dosage regimen. Therefore, CYP3A4 phenotyping could be useful to individualize sunitinib therapy. Additionally, sunitinib+SU12662 trough levels are highly predictive for sunitinib+SU12662 exposure and thus can be used for monitoring and guiding sunitinib therapy in clinical practice. Clinical trial information: NCT01743300.

Genetic variation in CYP19A1 and occurrence of adverse events in exemestane treatment with early breast cancer patients in the Dutch TEAM trial

e22152

Background: Aromatase inhibitors (AI) are an important part of treatment of endocrine sensitive breast cancer. Adverse events in patients treated with AI’s often cause treatment discontinuation. The most common adverse events, such as arthralgia, myalgia and hot flushes are probably caused by estrogen deprivation and predict treatment efficacy. It is unclear which patients are at risk to develop these adverse events. The aim of this study was to examine if SNP’s in the CYP19A1 gene can predict the occurrence of adverse events in breast cancer patients treated with adjuvant exemestane. Methods: Patients of whom tissue was available and were selected from the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial. DNA was isolated from tumor samples and 30 SNPs were identified using a tagging SNP approach, aiming for 80% coverage of CYP19A1. Genotypes were determined with taqman assays. Primary endpoint of the study was the occurrence of adverse events. Secondary endpoints were the occurrence of hot flushes, arthralgia, and myalgia. Results: 807 patients were included in the analyses and genotypes were obtained in 722 cases. One SNP, rs8031311, was associated with a higher incidence of adverse events with an odds ratio of 2.8. Four SNP's were associated with an increased incidence of hot flushes: rs934635, rs4775928, rs16964189, rs6493496 with odds ratio’s of 2.9, 1.8, 1.8 and 2.6 respectively. No association was found between variation in CYP19A1 and the occurrence of arthralgia or myalgia. Conclusions: Germline variation in the CYP19A1 gene is related to the occurrence of adverse events, specifically hot flushes, in early breast cancer patients treated with exemestane. These findings may contribute to the individualization of hormonal therapy in breast cancer. [Table: see text]

The influence of gastrointestinal resection on sunitinib exposure in GIST patients

10547

Background: GIST patients often have an altered anatomy of the GI tract due to either primary resection of the tumor or palliative surgery. It is unknown whether such GI resections affect the exposure to sunitinib and its active metabolite SU12662. Previous studies showed that the exposure to imatinib and nilotinib was decreased in GIST patients with prior major gastrectomy. Therefore, we postulated that GI resections might similarly affect sunitinib exposure. Methods: A retrospective analysis was performed to assess the effect of GI resections on sunitinib exposure. Pharmacokinetic data from 305 GIST patients included in 4 phase I-II trials were analyzed. Patients were subdivided into 6 groups according to prior GI surgery: 1)Major gastrectomy: 2)Partial gastrectomy: 3)Small bowel resection: 4)Combination of gastrectomy and small bowel resection: 5)Colon resection and 6)Controls with no prior GI surgery. Patients with uncertain GI resections were excluded. Dose normalized exposure (AUC0-24hr) of sunitinib and SU12662 was estimated with a population PK approach using NONMEM. Analysis of covariance was performed to test for significant differences in AUC between each of the subgroups and controls. Results: The geometric mean of total exposure to sunitinib and SU12662 was decreased by 21% and 28% in subgroup 4, (n=8; sunitinib: 931 ng*hr/mL (95%CI;676-1283) and SU12662: 354 ng*hr/mL (95%CI;174-720)) compared to controls (n=63; sunitinib: 1177 ng*hr/mL (95%CI;1097-1263) and SU12662: 491 ng*hr/mL (95%CI;435-555)), with the differences being significant (p<0.05) on the log scale. However, no significant differences in total exposures were observed between each of the other subgroups and control. Conclusions: In patients with a combined gastrectomy and small bowel resection, sunitinib and SU12662 exposure is significantly decreased as compared to subjects with no prior GI surgery. Contrary to previous results for imatinib, gastrectomy alone does not appear to influence sunitinib exposure. This should be taken into consideration for the treatment of GIST patients who had a gastrectomy. In theory, such patients might have better outcomes if treated with sunitinib, given the risk of subtherapeutic exposure to imatininb.

CYP2D6 genotype related to tamoxifen efficacy: An analysis with exclusion of potential false CYP2D6 genotype assignment caused by loss of heterozygosity in tumor tissue

597

Background: The clinical importance of CYP2D6 genotype as predictor of tamoxifen efficacy is still unclear. Recent genotyping studies on CYP2D6 using DNA derived from tumor blocks have been criticized because loss of heterozygosity (LOH) in tumors may lead to false genotype assignment. Methods: Postmenopausal early breast cancer patients who were randomized to receive tamoxifen, followed by exemestane in the Tamoxifen Exemestane Adjuvant Multinational trial (TEAM) were genotyped for 5 CYP2D6 variant alleles. CYP2D6 genotypes and phenotypes were related to disease free survival during tamoxifen use (DFS-t) in 731 patients. By analyzing three microsatellites flanking the CYP2D6 gene, patients whose genotyping results were potentially affected by LOH were excluded. Results: Analysis of the CYP2D6 alleles and the microsatellite markers demonstrated heterozygosity for at least one of the CYP2D6 alleles or microsatellite markers in 97.7% of patients with a specified CYP2D6 phenotype. The 14 patients (2.3%) with a homozygous CYP2D6 genotype in which no heterozygosity could be demonstrated for the microsatellite markers were excluded from the analysis. No association was found between the CYP2D6 genotype or predicted phenotype and DFS-t. Conclusions: In postmenopausal early breast cancer patients treated with adjuvant tamoxifen followed by exemestane neither CYP2D6 genotype nor phenotype was associated with DFS-t. This is in accordance with two recent studies in the BIG1-98 and ATAC trials. Our study is the first CYP2D6 association study using DNA from paraffin embedded tumor tissue in which potentially false interpretation of genotyping results because of LOH was excluded.

Pharmacokinetics (PK) of panitumumab in a single patient with metastatic colorectal cancer (mCRC) and liver dysfunction

594

Background: Panitumumab is used for the treatment of metastatic KRAS wild type (WT) colorectal cancer (mCRC). It is likely that many of these patients will present with liver metastases and some with liver dysfunction. The pharmacokinetics in patients with hepatic impairment are unknown and dosage adjustments are undetermined. Here, we present a case of a patient with progressive mCRC and liver dysfunction. Methods: A heavily pre-treated KRAS WT mCRC patient with liver disease Child-Pugh class B was treated with two-weekly 6 mg/kg panitumumab. The patient received 2 doses of 490 mg iv panitumumab after which progressive disease was documented. Toxicities were graded using CTCAEv4.0. Serum samples were collected and panitumumab concentrations were determined using a validated immunoassay. PK parameters after the first dose, including dose-normalized AUC from time zero–day 14, clearance (CL), and elimination half-life (T1/2), were estimated via trapezoidal non compartmental methods. Data was compared to historical data from a normal population as reported by Stephenson (Clin Colorectal Cancer 2009). Values within the range of the mean ± 1 standard deviation (SD) were considered not deviant. Results: Calculated AUC after the first dose of 6 mg/kg panitumumab in this patient with hepatic dysfunction was 877 μg*day/mL (Stephenson’s cohort 1: 744 ± 195 μg*day/mL). Estimated T1/2was 3.58 days (5.28 ± 1.90 days) and CL was 6.9 mL/day/kg (8.21 ± 3.79 mL/day/kg). Estimated PK parameters during the first cycle were inside reported mean ± 1 SD of historical controls without liver dysfunction. No toxicity was reported during treatment, particularly, no diarrhea and skin toxicity. Conclusions: The pharmacokinetics of panitumumab in this patient suffering from colorectal cancer with liver dysfunction Child-Pugh class B was similar when compared to patients with adequate liver functions. Moreover, no substantial toxicity was detected. The here presented data may help clinical decision making in real life practice. Two-weekly panitumumab monotherapy seems to be safely applicable in patients with KRAS WT mCRC and hepatic dysfunction without the need for dose adjustments.

Relationship between specific adverse events and efficacy of exemestane therapy in early postmenopausal breast cancer patients

BACKGROUND

Many adverse events (AEs) associated with aromatase inhibitors (AIs) involve symptoms related to the depletion of circulating estrogens, and may be related to efficacy. We assessed the relationship between specific AEs [hot flashes (HF) and musculoskeletal AEs (MSAE)] and survival outcomes in Dutch and Belgian patients treated with exemestane (EXE) in the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial. Additionally, the relationship between hormone receptor expression and AEs was assessed.

METHODS

Efficacy end points were relapse-free survival (RFS), overall survival (OS) and breast cancer-specific mortality (BCSM), starting at 6 months after starting EXE treatment. AEs reported in the first 6 months of treatment were included. Specific AEs comprised HF and/or MSAE. Landmark analyses and Cox proportional hazards models assessed survival differences up to 5 years.

RESULTS

A total of 1485 EXE patients were included. Patients with HF had a better RFS than patients without HF [multivariate hazard ratio (HR) 0.393, 95% confidence interval (CI) 0.19-0.813; P = 0.012]. The occurrence of MSAE versus no MSAE did not relate to better RFS (multivariate HR 0.677, 95% CI 0.392-1.169; P = 0.162). Trends were maintained for OS and BCSM. Quantitative hormone receptor expression was not associated with specific AEs.

CONCLUSIONS

Some AEs associated with estrogen depletion are related to better outcomes and may be valuable biomarkers in AI treatment.

Association of the genetic variants in the nucleotide excision repair genes XPA and XPC with cisplatin-induced hearing loss in patients with osteosarcoma

10077

Background: Cisplatin is a widely used and effective chemotherapeutic agent in the treatment of osteosarcoma. However, cisplatin-induced ototoxicity is a serious problem, affecting more than 60% of patients and compromising language and cognitive development. Unfortunately, individuals at risk to develop ototoxicity cannot be identified upfront. Genetic variants in genes involved in the metabolism of cisplatin may predispose to cisplatin-induced hearing loss and help to identify patients at risk. Methods: In a candidate gene pathway approach, we selected 224 SNPs in 30 candidate genes related to Platinum-DNA repair pathways and genotyped for a discovery group of 105 patients with osteosarcoma for these variants. Cisplatin-induced ototoxicity (n = 47), defined as the development of grade 2–4 hearing impairment using Common Terminology Criteria for Adverse Events (CTCAE version 3), showing a hearing loss of >25 dB at frequencies of 4–8 kHz, was associated with genetic variation. A replication study was performed in a independent cohort of 51 patients with osteosarcoma. Genotyping was performed using the Illumina GoldenGate assay. Association analysis and meta-analysis were performed using the whole genome association analysis toolset PLINK. Results: In the discovery cohort a total of 13 SNPs were significantly (p value < 0.05) associated with ototoxicity. Upon meta-analysis, addition of the replication set resulted in lower p-values for 2 SNPs. The two SNPs showing a strong association with hearing loss in patients with osteosarcoma were rs2805835 in the gene XPA (p-value 0.01, OR=2.7 (95%CI: 1.20-6.15) and rs2227999 in XPC (p-value 0.02; OR=3.2 (95% CI:1.19-8.80). Conclusions: The Nucleotide Excision Repair (NER) genes XPA and XPC form an important molecular mechanism by which cisplatin DNA adducts can be repaired and it has recently been shown that these genes have a high expression in the cochlea. Our data suggest that genetic variants in these genes, may contribute to cisplatin ototoxicity. This study should be viewed as the first step in the development of genetic markers to predict cisplatin-induced ototoxicity in individual patients.

Genetic variation in CYP19A1 and response to exemestane: Survival in early breast cancer in the Dutch TEAM trial

10518

Background: In patients with endocrine-sensitive breast cancer treated with adjuvant aromatase inhibitors (AI) it is unclear which patients will develop a recurrence and who will benefit from AI’s. Variations in the aromatase gene (CYP19A1) are associated with altered estrogen levels and altered aromatase activity. The aim of this study was to examine the effect of SNPs in the CYP19A1 gene on survival in a prospective cohort of breast cancer patients treated with adjuvant exemestane. Methods: Patients of whom tissue was available and who were treated with five years of exemestane were selected from the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial. DNA was isolated from tumor samples and 30 SNPs were identified using a tagging SNP approach, aiming for 80% coverage of CYP19A1. Genotypes were determined with taqman assays. Primary endpoint of the study was relapse-free survival (RFS) and secondary endpoint was overall survival (OS). A Kaplan-Meier analysis was performed and Cox proportional hazards models assessed survival differences. Analyses were adjusted for age at diagnosis, tumor size, nodal status, histological grade, surgery, adjuvant radiotherapy and chemotherapy. Results: 807 patients were included in the analyses and genotypes were obtained in 722 cases. A significant association with worse RFS was found with two SNPs: rs7176005 and rs16964211, showing hazard ratios (HR) of 3.48 and 5.42 for the homozygeous variant types respectively. These SNPs, as well as a third SNP, rs6493497, were also significantly associated with OS (HR 5.87, 5.3 and 3.36 respectively). Conclusions: Germline variations in the CYP19A1 gene are related to a worse outcome in early breast cancer patients treated with exemestane. These findings may contribute to the individualization of hormonal therapy in breast cancer. The relation between RFS and SNP’s in CYP19A1. [Table: see text]

Common polymorphisms in the estrogen receptor-1 may determine risk of hot flashes in early breast cancer patients using tamoxifen

526

Background: In breast cancer patients the occurrence of hot flashes as common side effect of tamoxifen therapy may be associated with effective estrogen receptor antagonism dependent on genetic variations of metabolic enzymes and the estrogen receptor. Methods: 742 early breast cancer patients who were randomized to receive tamoxifen, followed by exemestane after 2.5 to 3 years within the Tamoxifen Exemestane Adjuvant Multinational (TEAM) Trial were genotyped for 30 germ line genetic variants of 11 enzymes that are involved in the tamoxifen metabolism and the estrogen receptor 1 (ESR1). These genetic variants were related to the occurrence of hot flashes during the first year of tamoxifen use (primary aim) and during the complete tamoxifen treatment period (secondary aim). A multivariable logistic regression was used to adjust for age and adjuvant chemotherapy. Results: No genetic variant was associated with the occurrence of hot flashes during the first year. Higher age was related to a lower incidence of hot flashes in the first year (adjusted odds ratio 0.94, 95% CI 0.92-0.96; p<0.001). The ESR1 PvuII XbaI CG haplotype (CG/CG vs CG/other + other/other: adjusted odds ratio 0.44, 95% CI 0.21-0.92; p=0.03), ESR1 PvuII XbaI TA haplotype (TA/TA + TA/other vs other/other: adjusted odds ratio 1.86, 95% CI 1.09-3.14; p=0.02) and age (adjusted odds ratio 0.94, 95% CI 0.92-0.97; p<0.001) were associated with the occurrence of hot flashes during the total tamoxifen treatment period. No association was found between the CYP2D6 predicted phenotype and hot flashes. Conclusions: Common polymorphisms in the estrogen receptor-1 might help to predict the occurrence of hot flashes in breast cancer patients treated with adjuvant tamoxifen. If replicated, this may provide clinicians with a tool to offer more personalized hormonal therapy.

The tolerability and efficacy of low-dose simvastatin in statin-intolerant patients

BACKGROUND/AIM

Statin intolerance is increasingly recognized as a therapy limiting factor in the primary and secondary prevention of cardiovascular disease. Since vulnerability to dose related adverse events differ between subjects treated with statins we hypothesized low-dose simvastatin would be tolerated and effective in statin-intolerant patients.

METHOD

A single center open label prospective observational study was performed assessing tolerability and efficacy of low-dose simvastatin treatment in 35 statin-intolerant patients. Statin intolerance was defined as not being able to tolerate a registered dose statin due to myalgia-myopathy, myositis, or elevation of serum liver enzyme levels. These statin-intolerant patients were treated with simvastatin with an initial dose of 2.5mg every other day. The dose was titrated upwards if possible. Tolerability was defined as remaining on treatment. Efficacy was defined as change of LDL-cholesterol compared to baseline.

RESULTS

The reached simvastatin dose ranged from 0.825 to 8.75mg/day with a mean dose of 4mg/day. Fifty-seven percent of the patients tolerated low-dose therapy and remained on treatment. Of these patients, 30% noted recurrent myalgia. Low-dose simvastatin significantly decreased mean(SD) LDL-cholesterol levels with 25.9(12.1)% (p<0.001). Eleven percent of the patients reached LDL-cholesterol target levels (<2.6mmol/l) in an intention to treat analysis and in 20% of patients that tolerated low-dose simvastatin.

CONCLUSION

Low-dose simvastatin therapy is tolerated in a considerable proportion of statin-intolerant patients with significant lipid lowering efficacy. Low-dose statin therapy can be considered in multidrug regimens in statin-intolerant patients.

Pharmacogenetics in oncology: a promising field

Pharmacogenetics is a rapidly developing field, especially in oncology. In the most ideal situation pharmacogenetics will allow oncologists to individualize therapy based on patients' individual germline genetic test results. This can help to improve efficacy, reduce toxicity and predict non-responders in a way that alternative therapy can be chosen or individual dose adjustments can be made. Multiple pathways have been studied extensively of which a brief review is presented here. Increased 5FU toxicity is associated with variations in the DPYD gene, TYMS gene and MTHFR gene. Furthermore variations in the UGT1A gene and the ABCB1 gene influence irinotecan metabolism and disposition. Other genetic changes result in reduced DNA repair capacity related to platinum efficacy or reduced cytochrome P450 2D6 activity related to tamoxifen efficacy. Despite the extensive number of pharmacogenetic studies and promising results, it is still unclear when and how pretreatment genetic screening should be implemented in oncology. Future prospective studies should focus on the effect of pharmacogenetics on patient outcome and combine this with cost effectiveness evaluations. Thus supplying us with predictive models helping in deciding when pretreatment genetic screening is useful.

Time to treatment as an important factor for the response to methotrexate in juvenile idiopathic arthritis

OBJECTIVE

Methotrexate (MTX) is the most commonly used disease-modifying antirheumatic drug in juvenile idiopathic arthritis (JIA). Currently, individual response to MTX cannot be reliably predicted. Identification of clinical and genetic factors that influence the response to MTX could be helpful in realizing the optimal treatment for individual patients.

METHODS

A cohort of 128 JIA patients treated with MTX were studied retrospectively. Eleven clinical parameters and genotypes of 6 single nucleotide polymorphisms in 5 genes related to the mechanism of action of MTX were compared between MTX responders and nonresponders using a multivariate regression analysis.

RESULTS

The time from diagnosis to start of MTX treatment, physician's global assessment at baseline, and the starting dose were significantly associated with the response to MTX at 6 months after initiation. Patients with a shorter time from diagnosis to start of MTX and a higher disease activity according to the physician but with a lower MTX dose showed an increased response. The effect of the starting dose on MTX response seemed to be mainly due to the influence of the systemic JIA subtype. The time from diagnosis to start of MTX treatment and physician's global assessment at baseline were highly correlated. Therefore, the precise effect size of each independent variable could not be determined.

CONCLUSION

In children with JIA, the time from diagnosis to start of MTX appears to be an important factor for MTX response. Our results suggest that an earlier start of MTX treatment will lead to an increased response.

Is statin use associated with a reduced incidence, a reduced Breslow thickness or delayed metastasis of melanoma of the skin?

BACKGROUND

Statins show anticancer activity in melanoma cells. We investigated the association between statins and incidence and Breslow thickness of cutaneous melanoma (CM).

METHODS

Data were used from PHARMO, a pharmacy database, and PALGA, a pathological database, in the Netherlands. Cases had a primary CM diagnosis between January 1st 1991 and December 14th 2004, were 18 years and had 3 years of follow up in PHARMO before CM diagnosis. Controls were matched for gender, date of birth and geographic region. Analyses were adjusted for age, gender, year of diagnosis, number of medical diagnoses and the use of NSAIDs and oestrogens.

FINDINGS

Finally, 1318 cases and 6786 controls were selected. CM risk was not associated with statin use (> or = 0.5 years) (adjusted odds ratio (OR)=0.98, 95% confidence interval (CI)=0.78-1.2). However, statin use was associated with a reduced Breslow thickness (-19%, 95% CI=-33, -2.3, p=0.03).

CONCLUSION

Our study suggests protective effects of statins on melanoma progression.

Cyclopentenyl cytosine (CPEC): an overview of its in vitro and in vivo activity

The experimental cytotoxic drug cyclopentenyl cytosine (CPEC) is an analogue of cytidine. Besides its antiviral effect, its potential use in the treatment of cancer has become an important area of research. CPEC is activated by intracellular phosphorylation ultimately forming its metabolite CPEC-TP. CPEC-TP is a non competitive inhibitor of cytidine-5'-triphosphate synthetase (CTP-synthetase), an important enzyme in the formation of CTP. Studies have shown that cancer cells have a high CTP synthetase activity, thus making them interesting targets for chemotherapy. CPEC has been preclinically studied in different malignancy models. In vitro results on leukemia show activity in the nanomolar range on several cell lines. However in vivo results are conflicting and the findings vary from increase in life span over 100% to only limited effectiveness. Interesting results have been obtained in colorectal and neuroblastoma cells. In several neuroblastoma cell lines incubation with CPEC in combination with cytarabine or gemcitabine has resulted in increased cell death compared to incubation with with only one of the agents. CPEC has been studied in a phase I trial in patients with solid tumors. In five of 26 patients unexplained cardiotoxicity (extreme hypotension) occurred. The cardiotoxic effects could not be reproduced in animal models. However, precautions should be taken when using this drug in future clinical trials. Low dosage of CPEC seems necessary and intensive cardiac monitoring is advisable. In this manuscript, it is demonstrated that CPEC has an anti-cancer effect in several tumor models: CPEC might be a potentially useful drug in anticancer treatment.

Insights into the role of heritable genetic variation in the pharmacokinetics and pharmacodynamics of anticancer drugs

Pharmacogenetics in oncology will ideally allow oncologists to individualise therapy based on a genetic test result. Severe toxicity and clinically significant underdosing may be avoided, whereas predicted non-responders can be offered alternative therapy. This manuscript gives an overview of heritable variants in the genes of nine enzymes or pathways that have been studied most extensively in anticancer chemotherapy. Even though many pharmacogenetic association studies have been published, there is a need for more research. In particular, there is a need for replication of data and development of predictive models. Prospective trials are required to establish clinical value and cost-effectiveness of pharmacogenetic testing in oncology.

Association between CYP1A2 activity and riluzole clearance in patients with amyotrophic lateral sclerosis

AIMS

Riluzole is used in a fixed dosing schedule of 50 mg twice daily to treat patients with amyotropic lateral sclerosis (ALS), one form of motor neurone disease. The large variability in the pharmacokinetics of riluzole may be a factor contributing to its limited therapeutic benefit. Riluzole is assumed to be mainly metabolized by the cytochrome P450 enzyme 1A2 (CYP1A2). The aim of the study was to investigate the relationship between CYP1A2 activity and riluzole clearance with a view to optimize drug treatment.

METHODS

A group of 30 ALS patients participated in the study. In each patient the CYP1A2 activity was determined using caffeine as a metabolic probe. Riluzole clearance was estimated from serum drug concentration measurements followed by Bayesian fitting.

RESULTS

Riluzole clearance and the serum paraxanthine : caffeine (P/C) ratio showed a positive correlation (r = 0.693; P = 0.0002). Linear regression analysis identified the P/C ratio (beta: 1.16) and height (beta: 0.027) as independent predictors of riluzole clearance (adjusted r2 = 0.369).

CONCLUSIONS

The P/C ratio, used as measure of CYP1A2 activity, significantly correlated with the riluzole clearance, although only 37% of the observed variability could be explained.

A validated HPLC assay to monitor riluzole plasma or serum concentrations in patients with amyotrophic lateral sclerosis

A specific, accurate and precise high-performance liquid chromatographic assay was developed for the determination of riluzole, a drug used to treat patients with amyotrophic lateral sclerosis. Samples were treated by extraction with dichloromethane followed by reversed-phase chromatography with ultraviolet detection at 260 nm. Preset validation criteria were met from 20 to 2000 ng/mL with a linear response curve. Extraction recovery of riluzole was 65-76%. The accuracy of the method was 102-103%. Intra- and inter-day coefficients of variation were in the ranges 2.8-4.9% and 1.8-9.7%. A detection limit of 5 ng/mL was found. Determination of concentrations in serum and plasma resulted in similar results below 500 ng/mL. At higher values a matrix effect cannot be excluded. This presented method can be used to monitor plasma or serum levels in ALS patients treated with riluzole.

Pharmacokinetic-pharmacodynamic modeling of the inhibitory effect of erythromycin on tumour necrosis factor-alpha and interleukin-6 production

Erythromycin inhibits the production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL6) induced by heat-killed Streptococcus pneumoniae in human whole blood ex-vivo. The objective of the present study was to determine and characterize the concentration-effect relationship of this phenomenon in order to predict its possible clinical relevance. Six healthy volunteers received a single intravenous dose of 1000 mg erythromycin. Blood samples were obtained up to 4 h after drug administration. Samples were assayed for erythromycin concentrations and (after heat-killed Streptococcus pneumoniae stimulation) for TNF-alpha and IL6 concentrations. Effect vs. time data from individual subjects were fitted to the indirect response model with an Emax concentration-effect relationship. Simulations of these effects were performed for therapeutic intravenous and oral erythromycin dosage regimens. The geometric means of the values of Kin, Kout and EC50 were 15.4 microg/h, 0.82/h, 9.4 mg/L for TNF-alpha and 321 microg/h, 2.02/h, 18.3 mg/L for IL6. Simulations revealed a maximal inhibition of TNF-alpha concentrations of 35%, 50%, 16% and 27% at erythromycin dosages of 500 mg i.v., 1000 mg i.v., 500 mg p.o and 1000 mg p.o. q 6 h, respectively, whereas a maximal inhibition of IL6 of 29%, 44%, 13% and 22% are predicted for the respective regimens. The inhibitory effect of erythromycin on TNF-alpha and IL6 production can be adequately described by the indirect response model with an Emax concentration-effect relationship. Simulations predicted a substantial decrease of production of these cytokines at intravenous and to a much lesser extent at oral erythromycin dosage regimens.

Inter- and intraindividual variability of riluzole serum concentrations in patients with ALS

All patients with amyotrophic lateral sclerosis (ALS) are treated with the same dose of riluzole: 50 mg twice daily. Reasonably large interindividual differences in clearance of the drug have been reported. The relatively small group of patients with high blood concentrations of riluzole has probably primarily influenced the efficacy and the incidence of side-effects in the previously conducted clinical trials with riluzole. Individual dosing of the drug may, in the case of large interindividual differences in serum concentrations of the drug, be necessary in the future. Exact data concerning the plasma and serum concentrations of riluzole in patients with ALS, after standardized intake of the drug, diet and blood sampling are unknown so far. In this study, inter- and intraindividual variability of serum and plasma levels of riluzole in 21 patients with "probable" or "definite" ALS were determined. The interindividual variability of peak serum levels (coefficient of variation=74%) was significantly larger than intraindividual variability (p<0.001). Serum levels were not correlated with age or smoking status. The determination of a correlation between riluzole serum concentrations and survival of patients with ALS will be the aim of further studies.