The high prevalence of the poor and ultrarapid metabolite alleles of CYP2D6, CYP2C9, CYP2C19, CYP3A4, and CYP3A5 in Taiwanese population

Polymorphism of CYP3A4*18 is associated with anti-tuberculosis drug-induced hepatotoxicity

Aim: The association between cytochrome P450 (CYP) gene polymorphisms and anti-tuberculosis drug-induced hepatotoxicity (ATDH) was investigated in patients with or without pre-existing liver diseases (PLD). Materials & methods: We followed 164 tuberculosis subjects, 58 with PLD and 106 without PLD. Polymorphisms in CYP2D6, CYP2C9, CYP2C19, CYP3A4 and CYP3A5 were analyzed using the TaqMan® SNP genotyping assay.Results: The CYP3A4*18 heterozygous genotype was associated with ATDH (OR: 3.24, 95% CI: 1.06-9.86) regardless of PLD presence. Among subjects without PLD, CYP3A4*18 heterozygotes had significantly higher ATDH risk (OR: 9.10, 95% CI: 1.56-53.16). Conversely, in the PLD group, CYP3A4*18 heterozygotes had lower ATDH risk (OR: 0.21, 95% CI: 0.05-0.98).Conclusion: CYP3A4*18 genotype is linked to ATDH in tuberculosis patients, with differential effects based on PLD presence.

Post-therapy plasma concentrations of quetiapine in Taiwanese patients

AIMS

Quetiapine is widely used to treat psychiatric disorders such as major depression, generalized anxiety disorder, dysthymic disorder, and insomnia other than schizophrenia and bipolar disorder. This study investigated the diagnostic distribution of quetiapine use in patients in a psychiatric hospital, the doses of quetiapine prescribed, and the plasma concentrations (Cps) of quetiapine and active metabolites.

METHODS

We enrolled 107 patients who had been prescribed quetiapine for at least 4 weeks. Diagnoses, demographics, and concomitant medications were recorded. Blood sampling was performed in the morning, approximately 12 h after the before-bed dose of quetiapine.

RESULTS

Diagnoses comprised schizophrenia (n = 25), bipolar disorder (n = 51), major depression (n = 15), dysthymic disorder (n = 9), and others (n = 7). The daily dose (DD) of quetiapine ranged from 25 to 800 (175.9 ± 184.4) mg, with the mean Cp being 105.6 ± 215.3 ng/ml, with a mean Cps/DD ratio of 0.58 ± 0.55 ng/ml/mg. There was a moderate positive linear correlation between the dose and Cps of quetiapine (r = 0.60), and the interpatient variation in Cps/DD ratio was up to 26-fold.

CONCLUSION

Quetiapine is used in various doses to treat many psychiatric disorders other than psychosis, and it is usually prescribed as a secondary antipsychotic for symptoms such as insomnia or agitation. A wide interpatient variation of the Cps/DD ratio was noticed. Patients of East Asian descent may exhibit a 50% to 100% increase in the Cps/DD ratio for quetiapine compared with patients of Western descent.

CYP2C19 loss-of-function alleles predicts clinical outcomes in East Asian patients with acute myocardial infarction undergoing percutaneous coronary intervention and stenting receiving clopidogrel

Background

CYP2C19 loss-of-function (LOF) alleles reduce the effectiveness of clopidogrel and are associated with high rates of clinical events in patients undergoing percutaneous coronary intervention (PCI) and stenting in Northeast Asians. However, the prevalence and influence of CYP2C19 LOF alleles in Southeast Asians remain unclear.

Objectives

This study aims to retrospectively investigate the prevalence of CYP2C19 LOF alleles and clinical outcomes in East Asian patients taking clopidogrel and undergoing PCI.

Methods

Between June 2019 and June 2020, volunteer participants in a single medical center were consecutively selected. The genetic data of CYP2C19 were derived from the Taiwan Precision Medicine Initiative (TPMI). Patients receiving clopidogrel while undergoing PCI with stenting were retrospectively analyzed.

Results

A total of 999 patients (62.4 ± 11.1 years old, 83.7% men) were enrolled; 39.3% without the CYP2C19 LOF allele (normal metabolizers + rapid metabolizers, NM + RM); 44.9% with one LOF allele (intermediate metabolizers, IM); 15.7% with two LOF alleles (poor metabolizers, PM). The incidence of stroke was higher in the PM subgroup compared to the NM + RM subgroup or IM subgroup in patients presenting with acute myocardial infarction (AMI). The 1-year major adverse cardiac and cerebrovascular events (MACCE)-free survival rates in all participants were similar among the three groups. However, in the AMI group, the 1-year MACCE-free survival rates were significantly lower in the PM subgroup compared to the NM + RM subgroup or IM subgroup.

Conclusion

In East Asians presenting with AMI, CYP2C19 PM was associated with deleterious cardiovascular outcomes and stroke. Our results reinforce the crucial role of preemptive CYP2C19 genotyping in East Asian AMI patients receiving clopidogrel treatment.

Clopidogrel Use and CYP2C19 Genotypes in Patients Undergoing Vascular Intervention Procedure: A Hospital-Based Study

Purpose

Clopidogrel is widely used in coronary artery, peripheral arterial, and cerebrovascular disease. We aimed to study the association of the CYP2C19 phenotype with cardiovascular outcomes and interventional procedures in a hospital-based population.

Patients and Methods

This cross-sectional, retrospective study enrolled patients with prior exposure to clopidogrel at the Taichung Veterans General Hospital (TCVGH) using data extracted from the Taiwan Precision Medicine Initiative (TPMI). Data on the CYP2C19 phenotype, drug-prescription profile, comorbidities, vascular intervention procedures, and hospitalization due to acute myocardial infarction (AMI) or stroke of clopidogrel users were analyzed.

Results

From the 32,728 patients in the TCVGH-TPMI cohort, we selected 2687 clopidogrel users. A total of 400 (14.9%) clopidogrel poor metabolizers (PMs), 1235 (46.0%) intermediate metabolizers (IMs), and 1052 (39.2%) extensive metabolizers (EMs) were identified. The predominant loss-of-function allele is *2. In 2687 patients with clopidogrel exposure, the CYP2C19 PM phenotype was unassociated with hospitalization due to AMI or stroke after adjusting for comorbidities and carotid angiographies. Among the 1554 clopidogrel users who underwent cardiovascular intervention, 193 (12.4%) received two or more types of interventional procedures. Compared with non-PMs, patients with the PM phenotype had a higher risk of multiple carotid interventions (OR: 3.13, 95% CI: 1.19–8.22).

Conclusion

In this hospital-wide cohort, 8.2% were clopidogrel users, of which 14.9% were CYP2C19 PMs. The result of this study does not support universal genotyping of CYP2C19 in all clopidogrel users to identify risks for stroke and AMI. CYP2C19 PMs are more likely to undergo multiple carotid interventions than non-PMs. Prospective studies to investigate the association of the CYP2C19 genotype and carotid interventions and outcomes are needed to validate our results.

Clinical pharmacogenomics in action: design, assessment and implementation of a novel pharmacogenetic panel supporting drug selection for diseases of the central nervous system (CNS)

Background

Pharmacogenomics describes the link between gene variations (polymorphisms) and drug responses. In view of the implementation of precision medicine in personalized healthcare, pharmacogenetic tests have recently been introduced in the clinical practice. However, the translational aspects of such tests have been limited due to the lack of robust population-based evidence.

Materials

In this paper we present a novel pharmacogenetic panel (iDNA Genomics-PGx–CNS or PGx–CNS), consisting of 24 single nucleotide polymorphisms (SNPs) on 13 genes involved in the signaling or/and the metabolism of 28 approved drugs currently administered to treat diseases of the Central Nervous System (CNS). We have tested the PGx–CNS panel on 501 patient-derived DNA samples from a southeastern European population and applied biostatistical analyses on the pharmacogenetic associations involving drug selection, dosing and the risk of adverse drug events (ADEs).

Results

Results reveal the occurrences of each SNP in the sample and a strong correlation with the European population. Nonlinear principal component analysis strongly indicates co-occurrences of certain variants. The metabolization efficiency (poor, intermediate, extensive, ultra-rapid) and the frequency of clinical useful pharmacogenetic, associations in the population (drug relevance), are also described, along with four exemplar clinical cases illustrating the strong potential of the PGx–CNS panel, as a companion diagnostic assay. It is noted that pharmacogenetic associations involving copy number variations (CNVs) or the HLA gene were not included in this analysis.

Conclusions

Overall, results illustrate that the PGx–CNS panel is a valuable tool supporting therapeutic medical decisions, urging its broad clinical implementation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02816-3.

Relationship between CYP2D6 genotype, activity score and phenotype in a pediatric Thai population treated with risperidone

Recently, the Clinical Pharmacogenetics Implementation Consortium (CPIC) have revised recommendations for the translation of CYP2D6 genotype to phenotype. Changes affect phenotype grouping, as well as the value used to calculate activity score for the CYP2D6*10 allele to better reflect the substantially decreased activity of this allele which is the most frequent allele found in Asian populations. This study aimed to evaluate whether the lower value for CYP2D6*10 as recommended, and the revised phenotype groupings improve the relationship between CYP2D6 genotype and risperidone measures. One hundred and ninety-nine children and adolescents with autism treated with a risperidone-based regimen for at least four weeks were included. CYP2D6 genotype was determined using the Luminex xTAG CYP2D6 Kit assay and translated into phenotype using different translation methods. Plasma concentrations of risperidone and 9-hydroxyrisperidone were measured using LC/MS/MS. Plasma levels of risperidone, risperidone concentration/dose ratio, and risperidone/9-hydroxyrisperidone ratio in patients with an activity score < 1 were significantly higher than those ≥ 1 (P value < 0.001 for all three parameters). Plasma risperidone levels and risperidone concentration/dose ratios were significantly higher in intermediate metabolizers (defined as AS = 0.25–0.75) than normal metabolizer (defined as AS = 1–2) patients (1.44 vs. 0.23 ng/ml, P < 0.001 and 1.63 vs. 0.29 ng/ml/ng, P < 0.001, respectively) as well as risperidone/9-hydroxyrisperidone ratio (0.20 vs. 0.04, P < 0.001). This is the first study in an Asian population utilizing the revised CPIC-recommended method for translating the CYP2D6 genotype to phenotype. In addition to validating that CYP2D6 genetic variation significantly impacts risperidone metabolism, we demonstrated that revised value for the CYP2D6*10 was superior for genotype to phenotype translation. However, at least for risperidone, subjects with an activity score of 1 presented as phenotypic normal, and not intermediate metabolizers, suggesting that phenotype classification is substrate dependent.

Pharmacogenetics of tamoxifen therapy in Asian populations: from genetic polymorphism to clinical outcomes

BACKGROUND

Compared with western countries, Asian breast cancer patients have unique pathological and biological characteristics. Most of them are premenopausal women with HR positive. Tamoxifen as the first-line drug for premenopausal women with HR+ is involved in multiple enzymes and transporters during metabolizing and transporting process. Variants that cause decreased or inactive gene products leading to abnormal responses in tamoxifen therapy have well been studied in western countries, whereas such information is much less reported in Asian populations.

OBJECTIVE

In order to elucidate the relationship between genetic variants and tamoxifen-induced individual drug reactions in different Asian populations and further identify genotypes/phenotypes with potential therapeutic significance.

METHODS

We reviewed the frequencies of genetic variants in major enzymes and transporter genes involved in the metabolism and transport of tamoxifen across Asian populations as well as significant correlations between genotypes/metabolic phenotypes and metabolites concentrations or BC clinical outcomes.

RESULTS

Significant inter-ethnic differences in allele frequencies was found among Asian populations, such as CYP2D6*4, *10, *41, CYP2C9*2, ABCB1 C3435T and SLCO1B1*5, and CYP2D6*10/*10 is the most common genotype correlated with adverse clinical outcomes. Moreover, we summarized the barriers and controversies of implementing pharmacogenetics in tamoxifen therapy and concluded that more population-specific pharmacogenetic studies are needed in the future.

CONCLUSION

This review revealed more systematic pharmacogenomics of genes involved in the metabolism and transport besides CYP2D6, are required to optimize the genotyping strategies and guide the personalized tamoxifen therapy in Asian populations.

Comparison Between Aspirin and Clopidogrel in Secondary Stroke Prevention Based on Real-World Data

Background

Clopidogrel was thought to be superior to aspirin for secondary prevention of vascular diseases in clinical trials. In this study we assessed the safety and efficacy of clopidogrel versus aspirin in real‐world practice by using the Taiwan Stroke Registry.

Methods and Results

Patients with ischemic stroke (2006–2016) on aspirin or clopidogrel for secondary stroke prevention were identified in the Taiwan Stroke Registry. Stroke recurrence and mortality rates in patients receiving aspirin (N=34 679) were compared with those receiving clopidogrel (N=7611) during a 12‐month follow‐up period. Propensity score matching and conditional Cox proportional hazards regression model were applied to control confounding factors with 6443 patients in each group. After propensity score matching, stroke recurrence rates were comparable between groups, with 223 patients in the aspirin (3.46%) and 244 in the clopidogrel group (3.79%) (hazard ratio=1.13, 95% confidence interval=0.89–1.43, P=0.311). However, the mortality rate was significantly higher in the clopidogrel group (362 patients, 5.62%) than in the aspirin group (302 patients, 4.69%) (hazard ratio=1.30, 95% confidence interval=1.07–1.58, P=0.008). Results were consistent before and after propensity score matching.

Conclusions

Clopidogrel was as effective as aspirin for prevention of recurrent stroke in real‐world practice. However, the mortality rate was significantly higher in the clopidogrel than in the aspirin group.

Effect of CYP3A4 genetic polymorphisms on the genotoxicity of 4,4'-methylene-bis(2-chloroaniline)-exposed workers

OBJECTIVES

We investigated the relationship between 4,4'-methylene-bis(2-chloroaniline) (MBOCA) exposure and micronucleus (MN) frequency, and how this association was affected by genetic polymorphism of the cytochrome P450 enzyme (CYP3A4).

METHODS

We divided the study population into an exposed group (n=44 with total urine MBOCA ≥20 μg/g creatinine) and a control group (n=47 with total urine MBOCA <20 μg/g creatinine). Lymphocyte MN frequency (MNF) and micronucleated cell (MNC) frequency were measured by the cytokinesis-block MN assay method. MNF reported as the number of micronuclei in binucleated cells per 1000 cells, and MNC reported as the number of binucleated cells with the presence of MN per 1000 cells. CYP3A4 alleles were measured by PCR-based restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The mean MNF (6.11 vs 4.46 MN/1000 cells, p<0.001) and MNC (5.75 vs 4.15 MN/1000 cells, p<0.001) in the exposed workers was significantly higher than that in the controls. The CYP3A4 polymorphism A/A+A/G influenced the difference in the mean MNF (5.97 vs 4.38 MN/1000 cells, p<0.001) and MNC (5.60 vs 4.15 MN/1000 cells, p<0.001) between the MBOCA-exposed and control groups. After adjusting risk factors, the MNF level in the MBOCA-exposed workers was 0.520 MN cells/1000 cells (p<0.001) higher than the control group among the CYP3A4 A/A+A/G genotype. Similarly, the MNC level in the MBOCA-exposed workers was 0.593 MN/1000 cells (p<0.001) higher than the control group among the CYP3A4 A/A+A/G genotype. However, the difference in adjusted MNF and MNC between the exposed and control groups was not significant for the CYP3A4 polymorphism with the G/G genotype.

CONCLUSIONS

We recommend that lymphocytes MNF and MNC are good indicators to evaluate MBOCA genotoxicity. Individuals with the CYP3A4 polymorphism A/A and A/G genotypes appear to be more susceptible to MBOCA genotoxicity.

Developing and Evaluating the HRM Technique for Identifying Cytochrome P450 2D6 Polymorphisms

BACKGROUND

Cytochrome P450 2D6 is one of the important enzymes involved in the metabolism of many widely used drugs. Genetic polymorphisms of CYP2D6 can affect its activity. Therefore, an efficient method for identifying CYP2D6 polymorphisms is clinically important.

METHODS

We developed a high-resolution melting (HRM) analysis to investigate CYP2D6 polymorphisms. Genomic DNA was extracted from peripheral blood samples from 71 healthy individuals. All nine exons of the CYP2D6 gene were sequenced before screening by HRM analysis. This method can detect the most genotypes (*1, *2, *4, *10, *14, *21 *39, and *41) of CYP2D6 in Chinese.

RESULTS

All samples were successfully genotyped. The four most common mutant CYP2D6 alleles (*1, *2, *10, and *41) can be genotyped. The single nucleotides polymorphism (SNP) frequencies of 100C > T (rs1065852), 1039C > T (rs1081003), 1661G > C (rs1058164), 2663G > A (rs28371722), 2850C > T (rs16947), 2988G > A (rs28371725), 3181A > G, and 4180G > C (rs1135840) were 58%, 61%, 73%, 1%, 13%, 3%, 1%, 73%, respectively. We identified 100% of all heterozygotes without any errors. The two homozygous genotypes (1661G > C and 4180G > C) can be distinguished by mixing with a known genotype sample to generate an artificial heterozygote for HRM analysis. Therefore, all samples could be identified using our HRM method, and the results of HRM analysis are identical to those obtained by sequencing. Our method achieved 100% sensitivity, specificity, positive prediction value and negative prediction value.

CONCLUSION

HRM analysis is a nongel resolution method that is faster and less expensive than direct sequencing. Our study shows that it is an efficient tool for typing CYP2D6 polymorphisms.

High prevalence of CYP2C19*2 allele in Roma samples: study on Roma and Hungarian population samples with review of the literature

The purpose of our study was to characterise the CYP2C19*2 and CYP2C19*3 alleles in healthy Roma and Hungarian populations. DNA of 500 Roma and 370 Hungarian subjects were genotyped for CYP2C19*2 (G681A, rs4244285) and CYP2C19*3 (G636A, rs4986893) by PCR-RFLP assay and direct sequencing. Significant differences were found comparing the Roma and Hungarian populations in CYP2C19 681 GG (63.6 vs. 75.9%), GA (31.8 vs. 23.0%), AA (4.6 vs. 1.1%), GA+AA (36.4 vs. 24.1%) and A allele frequencies (0.205 vs. 0.125) (p<0.004). Striking differences were found between Roma and Hungarian samples in CYP2C19*1 (79.5 vs. 87.4%) and CYP2C19*2 (20.5 vs. 12.6%) alleles, respectively (p<0.001). None of the subjects was found to carry the CYP2C19*3 allele. Frequencies of the intermedier metabolizer phenotype defined by the *1/*2 genotype (0.318 vs. 0.230, p<0.005) and poor metabolizer predicted by the *2/*2 genotype (0.046 vs. 0.011, p<0.005) was significantly higher in Roma than in Hungarians, respectively. Genotype distribution of the Roma population was similar to those of the population of North India, however, a major difference was found in the frequency of the CYP2C19*2 allele, which is likely a result of admixture with European lineages. In conclusion, the frequencies of the CYP2C19 alleles, genotypes and corresponding extensive, intermediate and poor metabolizer phenotypes studied here in the Hungarian population are similar to those of other European Caucasian populations, but display clear differences when compared to the Roma population.

Genetic polymorphisms of cytochrome P450 enzymes 2C9 and 2C19 in a healthy Mongolian population in China

We examined the distribution of major allelic variants of CYP2C9 and CYP2C19 in the Mongolian population of China and compared it with that of other populations. The polymorphisms of CYP2C9 (including the CYP2C9*1, CYP2C9*2 and CYP2C9*3 alleles) and CYP2C19 (including the CYP2C19*1, CYP2C19*2 and CYP2C19*3 alleles) were analyzed in 280 healthy unrelated Chinese Mongolian subjects, using a PCR-RFLP assay. The frequencies of CYP2C9*1, *2 and *3 alleles were 0.97, 0.00 and 0.03, respectively. The frequencies of CYP2C19*1, *2 and *3 alleles were 0.72, 0.24 and 0.04, respectively. We did not find any differences in the allelic distribution of these two genes between age groups. However, the genotype frequency of CYP2C9 *1/*3 was significantly higher in males than in females. Compared with other populations, we found that the allele frequencies of the CYP2C9*2 and CYP2C9*3 allelic variants in this Mongolian population of China were similar to those reported for other Asian populations, with significant differences compared to Caucasians and African-Americans.

Effect of CYP2D6, CYP3A5, and MDR1 genetic polymorphisms on the pharmacokinetics of risperidone and its active moiety

Clinical studies suggest that plasma levels of risperidone and its active moiety (risperidone + 9-hydroxyrisperidone) correlate with adverse drug effects. The aim of this study is to evaluate the pharmacogenetic variability in the disposition of risperidone and the active moiety in healthy Chinese subjects. A 2-mg single dose of risperidone is orally administered to 23 healthy Chinese subjects. The risperidone and 9-hydroxyrisperidone serum concentrations are measured. The polymorphic alleles of CYP2D6*10, CYP3A5*3, MDR1 C1236T, G2677T/A, and C3435T are determined in each subject. The mean maximum plasma concentration and area under the time-concentration curve extrapolated to infinity for risperidone are significantly higher in subjects possessing the CYP2D6*10 allele than in those with the CYP2D6*1/*1 and *1/*10 genotype. For active moiety, the subjects who carry both homozygous CYP2D6*10 and homozygous CYP3A5*3 have 98% higher area under the time-concentration curve extrapolated to infinity and 59% higher maximum plasma concentration compared with other CYP2D6 EM subjects. The MDR1 2677GA genotype may also play a role in risperidone pharmacokinetics. Further studies are needed to explore the impact of MDR1 2677GA and CYP3A5 polymorphisms on risperidone therapy.

Effect of cytochrome P450 polymorphism on arachidonic acid metabolism and their impact on cardiovascular diseases

Cardiovascular diseases (CVDs) remain the leading cause of death in the developed countries. Taking into account the mounting evidence about the role of cytochrome P450 (CYP) enzymes in cardiovascular physiology, CYP polymorphisms can be considered one of the major determinants of individual susceptibility to CVDs. One of the important physiological roles of CYP enzymes is the metabolism of arachidonic acid. CYP epoxygenases such as CYP1A2, CYP2C, and CYP2J2 metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which generally possess vasodilating, anti-inflammatory, anti-apoptotic, anti-thrombotic, natriuretic, and cardioprotective effects. Therefore, genetic polymorphisms causing lower activity of these enzymes are generally associated with an increased risk of several CVDs such as hypertension and coronary artery disease. EETs are further metabolized by soluble epoxide hydrolase (sEH) to the less biologically active dihydroxyeicosatrienoic acids (DHETs). Therefore, sEH polymorphism has also been shown to affect arachidonic acid metabolism and to be associated with CVDs. On the other hand, CYP omega-hydroxylases such as CYP4A11 and CYP4F2 metabolize arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) which has both vasoconstricting and natriuretic effects. Genetic polymorphisms causing lower activity of these enzymes are generally associated with higher risk of hypertension. Nevertheless, some studies have denied the association between polymorphisms in the arachidonic acid pathway and CVDs. Therefore, more research is needed to confirm this association and to better understand the pathophysiologic mechanisms behind it.

Novel DNA sequence variations of cytochrome P450 genes in the Han Chinese population

Aim: Cytochrome P450 is an important monooxygenase responsible for the metabolism of a large variety of structurally diverse compounds. The aim of this study was to systematically investigate the DNA sequence variations in 14 cytochrome P450 genes relevant to drug metabolism in the Han Chinese population. Materials & methods: We sequenced these 14 genes in 23 subjects and determined the allele frequencies. Results: We identified a total of 312 genetic variants, which included 80 (25.6%) novel variants. These novel variants included 67 noncoding variants, four synonymous and nine nonsynonymous variants. Among these variants, an 11-nucleotide insertion in the 3´-flanking site of intron 6 in CYP2E1 (c.968-77_-76insGATGGGTGGAT) had the highest allele frequency of 0.565. A total of 16 of these novel variants were predicted to have potential functional consequences; however, among them only c.-1299T>A in CYP2C18 and c.-498C>A in CYP2D6 reached a frequency of 4.9%. Conclusions: This study establishes a genetic database of cytochrome P450 genes in the Han Chinese population and suggests further genetic diversity throughout this important gene family.

Tamoxifen, soy, and lifestyle factors in Asian American women with breast cancer

PURPOSE

Soy foods have been a staple in Asia for centuries but the consumption of this food in the West is recent. Intake of soy among women at high risk for or with breast cancer has become a public health concern because genistein, a major component of soy, has weak estrogenic effects on breast epithelium, and has been found to negate the benefit of tamoxifen in some animal and in vitro studies.

PATIENTS AND METHODS

We conducted a cross-sectional study in Asian Americans with breast cancer who were tamoxifen users (n = 380) to investigate the association between soy intake and circulating levels of tamoxifen and its metabolites (N-desmethyl tamoxifen [N-DMT], 4-hydroxytamoxifen [4-OHT], and 4-hydroxy-N-desmethyl-tamoxifen [endoxifen]).

RESULTS

Serum levels of tamoxifen or its metabolites were unrelated to self-reported intake of soy or serum levels of isoflavones. Blood levels of tamoxifen were 81% higher in postmenopausal women age 65 or older compared with premenopausal women age 45 or younger (P = .005); similar patterns of results were observed for the tamoxifen metabolites. Levels of N-DMT were 27% (P = .03) lower among women in the highest tertile of body mass index (BMI, > 24.4 kg/m2) compared with those in the lowest category (BMI 21.5). Women who used hypertensive medications had higher levels of tamoxifen (P = .02) and N-DMT (P = .04) compared with nonusers.

CONCLUSION

We found no evidence that soy intake adversely affected levels of tamoxifen or its metabolites. However, age, menopausal status, BMI, and use of hypertensive medications significantly influenced circulating levels of tamoxifen and its metabolites in this population.