Cytochrome P450 2D6 and outcomes of adjuvant tamoxifen therapy: results of a meta-analysis

Pharmacological evidence shows that cytochrome P450 2D6 (CYP2D6) function is important in the conversion of tamoxifen to its active metabolites. Many retrospective analyses have assessed the role of both CYP2D6 genotype and concurrent administration of drug inhibitors of CYP2D6 on outcome of tamoxifen therapy. These studies have frequently been of small size and their data highly variable. A published data meta-analysis of trials evaluating outcomes of tamoxifen therapy in early breast cancer was undertaken. Hazard ratios (HRs) were extracted for disease-free survival (DFS) and overall survival (OS). Pooled estimates were computed using inverse-variance and random-effect modeling. Data from 10 studies assessing CYP2D6 genotype were included in a meta-analysis. There was significant heterogeneity in the definition of comparison groups between studies. When compared to reduced CYP2D6 function, normal function was associated with a trend toward improved DFS (HR 2.07, 95% CI 0.96–4.49, P = 0.06) but not OS (HR 1.36, 95% CI 0.73–2.52, P = 0.34). Pooling of data from two studies evaluating CYP2D6 drug inhibitors showed that concomitant administration of these with tamoxifen was associated with a non-significant association with DFS (HR 1.37, 95% CI 0.69–2.73, P = 0.37). Analysis of the effect of CYP2D6 drug inhibitors on OS was not possible. The effect of CYP2D6 genotype on breast cancer seems to be relatively small and may not warrant testing of CYP2D6 genotype in all women with hormone receptor positive breast cancer. The effect of CYP2D6 genotype on outcome in low-risk patients may not be clinically relevant, while the upfront use of aromatase inhibitors is a reasonable alternative to tamoxifen in high-risk post-menopausal women, irrespective of CYP2D6 genotype. There are limited data supporting the association of potent inhibitors of CYP2D6 and detrimental outcome, but avoidance of such drugs seems reasonable.     

Lack of any association between functionally significant <Emphasis Type="Italic">CYP2D6</Emphasis> polymorphisms and clinical outcomes in early breast cancer patients receiving adjuvant tamoxifen treatment

Active metabolites of tamoxifen are formed mainly by the action of cytochrome P450 2D6 (CYP2D6). Since there are controversies regarding associations between CYP2D6 polymorphisms and outcomes among women with early breast cancer (EBC) treated with tamoxifen, the present evaluation of links with clinical outcomes was conducted. We analyzed a total of 716 patients treated with tamoxifen for hormone receptor positive EBC between 2001 and 2005 at the National Cancer Center, Korea. All patients received tamoxifen 20 mg/day for more than 6 months. DNA obtained from whole blood samples was genotyped for CYP2D6 variants associated with reduced (*10, *41) and absent (*5) activity. Of the total of 716 patients, 558 (77.9%) received adjuvant or neoadjuvant chemotherapy prior to the tamoxifen therapy. From the genotyping of CYP2D6, 152 (21.2%) patients were classified as having the wild type (W/W), 376 (52.7%) one variant allele (W/V), and 188 (26.1%) two variant alleles (V/V). Seventy (9.8%) patients experienced disease recurrence with a median follow-up of 5.6 (range, 0.6–10.3) years. Although known prognostic factors, including tumor size, nodal status, Ki67, PgR negativity, and HER2 positivity showed strong associations with the recurrence free survival (RFS) in this population, no significant association with any of the CYP2D6 genetic variants was evident (P = 0.61; hazard ratio [HR] = 1.14; 95% CI 0.68–1.92). This remained the case after subgroup analysis according to different adjuvant treatments. Polymorphisms of CYP2D6 were not associated with clinical outcomes in EBC patients receiving adjuvant tamoxifen treatment.     

The CYP2D6*4 polymorphism affects breast cancer survival in tamoxifen users

Cytochrome P450 2D6 (CYP2D6) plays an important role in the formation of endoxifen, the active metabolite of tamoxifen. In this study the association between the most prevalent CYP2D6 null-allele in Caucasians (CYP2D6*4) and breast cancer mortality was examined among all incident users of tamoxifen in a population-based cohort study. Breast cancer mortality was significantly increased in patients with the * 4/*4 genotype (HR = 4.1, CI 95% 1.1–15.9, P = 0.041) compared to wild type patients. The breast cancer mortality increased with a hazard ratio of 2.0 (CI 95% 1.1–3.4, P = 0.015) with each additional variant allele. No increased risk of all-cause mortality or all-cancer mortality was found in tamoxifen users carrying a CYP2D6*4 allele. The risk of breast cancer mortality is increased in tamoxifen users with decreased CYP2D6 activity, consistent with the model in which endoxifen formation is dependent on CYP2D6 activity.     

Breast cancer in young women

The aim of this study is to evaluate the impact of CYP2D6 genotyping in predicting disease-free survival and toxicity in breast cancer patients treated with adjuvant tamoxifen. DNA from 91 patients was genotyped using the AmpliChip CYP450 GeneChip^®, Roche that facilitates the classification of individuals by testing 27 alleles. When patients were grouped into group 1 (*4/*4, *4/*41, *1/*5 and *2/*5) and group 2 (the remaining genotypes), a significant difference in disease-free survival (DFS) was observed between groups (P = 0.016). The mean DFS in group 1 was 95 months in contrast with 119 months in group 2. No significant relationship was found between the CYP2D6 genotype classification and severe, mild or no toxicity (P = 0.2). Nevertheless, severe, and mild toxicity was more frequent among poor metabolizer patients than in patients with a normal metabolizer pattern (18.8 and 43.8% vs. 10.7 and 36%, respectively). In breast cancer, patients treated with adjuvant tamoxifen, non-functional and severely impaired CYP2D6 variants are associated with a worse DFS and with a higher frequency of severe and mild toxicities. Larger studies of the CYP2D6 genotype-clinical outcomes association are needed to complement initial results.     

Utility of CYP2D6 copy number variants as prognostic biomarker in localized anal squamous cell carcinoma

Background

Anal squamous cell carcinoma (ASCC) is an infrequent tumor whose treatment has not changed since the 1970s. The aim of this study is the identification of biomarkers allowing personalized treatments and improvement of therapeutic outcomes.

Methods

Forty-six paraffin tumor samples from ASCC patients were analyzed by whole-exome sequencing. Copy number variants (CNVs) were identified and their relation to disease-free survival (DFS) was studied and validated in an independent retrospective cohort of 101 ASCC patients from the Multidisciplinary Spanish Digestive Cancer Group (GEMCAD). GEMCAD cohort proteomics allowed assessing the biological features of these tumors.

Results

On the discovery cohort, the median age was 61 years old, 50% were males, stages I/II/III: 3 (7%)/16 (35%)/27 (58%), respectively, median DFS was 33 months, and overall survival was 45 months. Twenty-nine genes whose duplication was related to DFS were identified. The most representative was duplications of the CYP2D locus, including CYP2D6, CYP2D7P, and CYP2D8P genes. Patients with CYP2D6 CNV had worse DFS at 5 years than those with two CYP2D6 copies (21% vs. 84%; p < .0002, hazard ratio [HR], 5.8; 95% confidence interval [CI], 2.7–24.9). In the GEMCAD validation cohort, patients with CYP2D6 CNV also had worse DFS at 5 years (56% vs. 87%; p = .02, HR = 3.6; 95% CI, 1.1–5.7). Mitochondria and mitochondrial cell-cycle proteins were overexpressed in patients with CYP2D6 CNV.

Conclusions

Tumor CYP2D6 CNV identified patients with a significantly worse DFS at 5 years among localized ASCC patients treated with 5-fluorouracil, mitomycin C, and radiotherapy. Proteomics pointed out mitochondria and mitochondrial cell-cycle genes as possible therapeutic targets for these high-risk patients.

Plain Language Summary

• Anal squamous cell carcinoma is an infrequent tumor whose treatment has not been changed since the 1970s.
• However, disease-free survival in late staged tumors is between 40% and 70%.
• The presence of an alteration in the number of copies of CYP2D6 gene is a biomarker of worse disease-free survival.
• The analysis of the proteins in these high-risk patients pointed out mitochondria and mitochondrial cell-cycle genes as possible therapeutic targets.
• Therefore, the determination of the number of copies of CYP2D6 allows the identification of anal squamous carcinoma patients with a high-risk of relapse that could be redirected to a clinical trial.
• Additionally, this study may be useful to suggest new treatment strategies to increase current therapy efficacy.

     

The relationship between the CYP2D6 polymorphisms and tamoxifen efficacy in adjuvant endocrine therapy of breast cancer patients in Chinese Han population

Variants of the CYP2D6 gene may lead to a poor prognosis of tamoxifen (TAM)‐treated patients. Our study validated the association between the CYP2D6 genotype and outcomes of patients receiving TAM in adjuvant endocrine therapy. A total of 778 breast cancer patients who received adjuvant TAM (n = 325) or aromatase inhibitors (AIs) (n = 453) at the National Cancer Center were analyzed. Nine single nucleotide polymorphisms (SNPs) in the CYP2D6 gene were selected from online databases. The associations of each SNP genotype with disease‐free survival (DFS) and clinicopathological characteristics were analyzed. A total of 167 (21.5%) patients carried the CYP2D6*10 (c.100C>T) T/T genotype. Among the 325 patients who received TAM, the 5‐year DFS rate was considerably lower in CYP2D6*10 T/T genotype patients than C/C or C/T patients (54.9% vs. 70.9%, p = 0.007). The T/T genotype for CYP2D6*10 was a significant prognostic marker for DFS in multivariate analysis (hazard ratio = 1.87; p = 0.006). The CYP2D6*10 genotype in women who received AIs was not significantly associated with DFS (p = 0.332). Other SNPs were not related to the survival of patients who received TAM. Our finding showed patients with CYP2D6*10 T/T received less benefit from TAM adjuvant treatment. This conclusion may optimize the individualized treatments for this subgroup of patients.     

Effect of CYP2D6 polymorphisms on breast cancer recurrence

BACKGROUND:

Previous studies evaluating the effect of cytochrome P450 2D6 (CYP2D6) polymorphisms on outcomes of adjuvant tamoxifen therapy have been conflicting due to differences in study design, concomitant medications that alter CYP2D6 metabolism, and tamoxifen adherence.

METHODS:

The authors performed CYP2D6 genotyping from whole blood and fresh frozen tumor samples (n 106) in patients at The University of Texas MD Anderson Cancer Center who were receiving, or had received, tamoxifen as adjuvant therapy for early breast cancer (EBC), using the AmpliChip CYP450 Test. Each patient's medical history was assessed for drugs that affected CYP2D6. Fifty‐five patients who had experienced breast cancer recurrence were matched (by date of diagnosis, menopausal status, clinical stage [TNM Staging System], and race) to patients without recurrence.

RESULTS:

Unadjusted for other patient characteristics, the odds ratio for disease recurrence associated with CYP2D6 functional status was 1.0 (95% confidence interval, 0.35‐2.85). After adjustment for stage, CYP2D6 inhibitors (moderate or strong vs none), and follow‐up time, no significant association was found between CYP2D6 genotype and breast cancer recurrence in patients who were treated with adjuvant tamoxifen for EBC.

CONCLUSIONS:

This case‐control study demonstrated no significant effect of CYP2D6 genotype on risk of recurrence in breast cancer patients who received adjuvant tamoxifen therapy. Cancer 2012;. © 2011 American Cancer Society.     

Prognosis of uterine corpus cancer after tamoxifen treatment for breast cancer

Tamoxifen increases the risk of uterine corpus cancer. Since only few, mostly small, studies have examined prognosis of uterine corpus cancer following tamoxifen, we conducted a large retrospective cohort study to further investigate this. We examined histopathologic and immunohistochemical characteristics of 332 patients with uterine corpus cancer following breast cancer, according to tamoxifen use. Survival was examined in the same patients combined with 309 patients from a previous study with updated follow-up. Histological review of all cancers was performed. Long-term tamoxifen users showed a higher proportion of non-endometrioid tumors than non-users (32.7% vs. 17.4%, P = 0.004), especially serous adenocarcinomas and carcinosarcomas. An increased proportion of FIGO stage III and IV tumors was also observed (20.0% vs. 11.3%, P = 0.049). Within FIGO stage I, both short-term and long-term tamoxifen users showed a higher proportion of tumors limited to the endometrium than non-users (35.7% vs. 22.9%, P = 0.049 and 0.004 respectively). Uterine corpus cancers in long-term tamoxifen users were more often steroid receptor-negative (ERα, PRA and PRB, P < 0.05) and P53-positive (P = 0.015). Three-year uterine corpus cancer-specific survival was worse for long-term tamoxifen users than for non-users (82% vs. 93% P = 0.0001). The survival difference remained after adjustment for histopathologic and immunohistochemical characteristics (hazard ratio (HR) for ≥2 years tamoxifen = 2.4; 95% CI = 1.2–4.6). In conclusion, this large study clearly shows that tamoxifen-associated tumors have less favorable histological features and a worse survival. Our results can be applied when weighing risks and benefits of tamoxifen versus other hormonal agents used in the prevention and treatment of breast cancer. TAMARISK (Tamoxifen Associated Malignancies: Aspects of Risk)-group of the Comprehensive Cancer Centers (CCC): O. Visser (CCC Amsterdam), R. A. M. Damhuis (CCC Rotterdam), W. J. Louwman (CCC South Netherlands), J. A. A. M. van Dijck (CCC East Netherlands), Y. Westerman (CCC Middle Netherlands), M. J. M. Dirx (CCC Limburg), M. L. E. A. Jansen-Landheer (CCC West), L. de Munck (CCC Northern Netherlands), S. Siesling (CCC Stedendriehoek Twente).     

Impact of CYP2D6 Polymorphisms on Tamoxifen Responses of Women with Breast Cancer: A Microarray-based Study in Thailand

This study was designed to investigate the frequency of CYP2D6 polymorphisms and evaluate the associationbetween genetic polymorphisms of CYP2D6 and tamoxifen therapeutic outcome in Thai breast cancer patients.We recruited 48 breast cancer patients who received adjuvant tamoxifen for evaluating CYP2D6 geneticpolymorphisms using microarray-based technology. Associations between genotypes-phenotypes and diseasefree survival were analyzed. Median follow up time was 5.6 years. The mean age of the subjects was 50 years.The 3 common allelic frequencies were 43.8% (*10), 36.5 (*1) and 10.4% (*2) which are related to extensivemetabolizer (EM) and intermediate metabolizer (IM) with 70.8% and 29.2 %, respectively. No associationbetween CYP2D6 genotypes and DFS was demonstrated. Nevertheless, exploratory analysis showed statisticallysignificant shorter DFS in the IM group of post-menopause patients (HR, 6.85; 95% CI, 1.48 –31.69; P = 0.005).Furthermore, we observed statistically significant shorter DFS of homozygous CYP2D6*10 when comparedwith heterozygous CYP2D6*10 and other genotypes (P=0.005). CYP2D6*10 was the most common genotype inour subjects. Post-menopause patients with homozygous CYP2D6*10 and IM have shorter DFS. To confirm thisrelationship, larger samples and comprehensively designed trials in Thailand are required.     

Association between CYP2D6 *10 genotype and survival of breast cancer patients receiving tamoxifen treatment

BackgroundHuman cytochrome P450 2D6 (CYP2D6) genotype may affect the efficacy of tamoxifen treatment in Caucasian women with breast cancer. The most common polymorphism of CYP2D6 in Chinese women is variant 10 (188 C to T).Patients and methodsTamoxifen and 4-hydroxytamoxifen (4OHtam) were measured in the serum of 37 women with breast cancer who were receiving tamoxifen treatment. The association between CYP2D6 *10 genotype and survival was determined in a cohort of 293 women with breast cancer who received tamoxifen (n = 152) or who did not (n = 141).ResultsThe serum 4OHtam concentrations were significantly lower in women with the CYP2D6 *10 homozygous variant T/T genotype than in those with the homozygous wild-type C/C genotype (P = 0.04). Among tamoxifen-treated women, women with the T/T genotype had a significantly worse disease-free survival (DFS) than those with the C/C or C/T genotype, and the T/T genotype remained an independent prognostic factor of DFS in multivariate analysis (hazard ratio = 4.7; 95% confidence interval = 1.1–20.0; P = 0.04). Among women who did not receive tamoxifen, there was no significant association between CYP2D6 *10 genotype and survival.ConclusionIn tamoxifen-treated patients, women with the CYP2D6 *10 T/T genotype have a lower 4OHtam level in the serum and a worse clinical outcome.     

Impaired tamoxifen metabolism reduces survival in familial breast cancer patients

PURPOSE: Tamoxifen has been the mainstay adjuvant hormonal treatment for breast cancer for many years. Conversion of tamoxifen to its active metabolite, endoxifen, is reduced by low activity of the cytochrome P450 enzyme, CYP2D6. We examined the effect of reduced CYP2D6 activity on the response to tamoxifen in patients with familial early-onset breast cancer. EXPERIMENTAL DESIGN: We conducted a case note review and genotyping for the CYP2D6*3, CYP2D6*4, CYP2D6*5, and CYP2D6*41 alleles in 115 patients (47 BRCA1, 68 BRCA2) with familial breast cancer who had been treated with 20-mg tamoxifen following surgery. RESULTS: Eight (7%) individuals had genotypes consistent with poor metabolizer status, and 4 (3.5%) individuals took CYP2D6 inhibitor drugs concomitant with their tamoxifen and were also considered poor metabolizer. Time to tumor recurrence, disease-free survival, and overall survival were reduced in the patient group with poor metabolizer CYP2D6 activity. However, a significant effect was confined to patients with BRCA2 mutations with a worse overall survival (median survival, 7 versus 28 years; P = 0.008; adjusted hazard ratio, 9.7). CONCLUSIONS: Poor metabolizer status for CYP2D6 predicts worse overall survival in patients with familial breast cancer. Therefore, CYP2D6 inhibitor drugs should not be prescribed concomitantly with tamoxifen. Prospective studies should be undertaken to establish the effect of CYP2D6 status on outcome in familial breast cancer patients treated with tamoxifen.     

Dose-adjustment study of tamoxifen based on <Emphasis Type="Italic">CYP2D6</Emphasis> genotypes in Japanese breast cancer patients

CYP2D6 is a key enzyme responsible for the metabolism of tamoxifen to active metabolites, endoxifen, and 4-hydroxytamoxifen. The breast cancer patients who are heterozygous and homozygous for decreased-function and null alleles of CYP2D6 showed lower plasma concentrations of endoxifen and 4-hydroxytamoxifen compared to patients with homozygous-wild-type allele, resulting in worse clinical outcome in tamoxifen therapy. We recruited 98 Japanese breast cancer patients, who had been taking 20 mg of tamoxifen daily as adjuvant setting. For the patients who have one or no normal allele of CYP2D6, dosages of tamoxifen were increased to 30 and 40 mg/day, respectively. The plasma concentrations of tamoxifen and its metabolites were measured at 8 weeks after dose-adjustment using liquid chromatography–tandem mass spectrometry. Association between tamoxifen dose and the incidence of adverse events during the tamoxifen treatment was investigated. In the patients with CYP2D6*1/*10 and CYP2D6*10/*10, the mean plasma endoxifen levels after dose increase were 1.4- and 1.7-fold higher, respectively, than those before the increase (P < 0.001). These plasma concentrations of endoxifen achieved similar level of those in the CYP2D6*1/*1 patients receiving 20 mg/day of tamoxifen. Plasma 4-hydroxytamoxifen concentrations in the patients with CYP2D6*1/*10 and CYP2D6*10/*10 were also significantly increased to the similar levels of the CYP2D6*1/*1 patients according to the increasing tamoxifen dosages (P < 0.001). The incidence of adverse events was not significantly different between before and after dose adjustment. This study provides the evidence that dose adjustment is useful for the patients carrying CYP2D6*10 allele to maintain the effective endoxifen level.     

CYP2D6 phenotype indicative for optimized antiestrogen efficacy associates with outcome in early breast cancer patients

Background

Endoxifen serum concentrations seem to correlate with outcome in breast cancer (BC) patients. Concurrently, cytochrome P450 2D6 (CYP2D6) enzyme activity and dextromethorphan (DM) metabolism are deemed a surrogate marker for the formation of endoxifen. Here, we conducted a matched cohort study to determine the impact of an extensive CYP2D6 phenotype on relapse in patients with early-stage estrogen receptor (ER)-positive BC and adjuvant tamoxifen intake.

Methods

CYP2D6 extensive metabolism was determined upon appropriate dextromethorphan/dextrorphan (DM/DX) urinary excretion ratios (≤0.30). Fifty-nine BC patients were identified as extensive phenotype metabolizers, while for 148 matched controls, CYP2D6 was not determined. Patients and controls did not differ with respect to age, stage, hormone receptor status, HER2, grade, menopausal status, chemotherapy and antihormonal therapy. Survival analysis was performed according to clinical follow-up.

Results

Disease-free survival (DFS) of patients identified as extensive CYP2D6 metabolizers did not differ significantly from controls (p = 0.10). However, when patients with ER expression of ≤20 % were excluded from the analysis, DFS was associated with a more favorable outcome (p = 0.06).

Conclusions

This study suggests a positive association between extensive CYP2D6 metabolism and outcome in early-stage ER-positive BC patients using tamoxifen and in particular, when a sufficient number ERs are represented on the primary tumor.     

Pharmacogenomics of Tamoxifen: Ready for Prime Time?

Tamoxifen is the most common hormonal therapy prescribed to women with hormone receptor-positive breast cancer. Tamoxifen requires metabolic activation by the CYP2D6 enzyme to form its active metabolite endoxifen. However, the activity of CYP2D6 is highly variable. Women who are poor metabolizers due to genetic polymorphisms in the gene encoding for a null or low activity enzyme or due to concomitant use of a potent inhibitor have a significantly lower concentration of endoxifen compared with those with one or two wild-type genes (intermediate or extensive metabolizers, respectively). The past few years have seen a spurt in studies evaluating the role of CYP2D6 genotype as a predictor of tamoxifen-associated outcomes. Although the majority of studies have reported a positive association between poor metabolizers of CYP2D6 and worse breast cancer outcomes among women taking adjuvant tamoxifen, other studies have reported opposite results. Due to the retrospective nature and other limitations associated with the majority of studies published to date, the standard incorporation of CYP2D6 genotype testing of all women who are candidates for tamoxifen cannot be recommended. Nevertheless, there are certain circumstances where CYP2D6 testing might be helpful, and the decision should be individualized. Importantly, tamoxifen users should avoid the concomitant use of potent CYP2D6 inhibitors, such as paroxetine, and consider non-inhibitors, such as venlafaxine, for hot flashes or psychiatric conditions. A deeper understanding of interaction between host polymorphisms, tumor biology, and environmental factors will optimize the therapeutic potential of tamoxifen and successfully transform the promise of personalized medicine into reality.     

The impact of CYP2D6-predicted phenotype on tamoxifen treatment outcome in patients with metastatic breast cancer

Background:

Cytochrome P450 2D6 (CYP2D6) has a crucial role in the metabolic conversion of tamoxifen into the active metabolite endoxifen. In this cohort study, the effect of CYP2D6-predicted phenotype, defined as the combined effect of CYP2D6 genetic variation and concomitant use of CYP2D6-inhibiting medication, on time to breast cancer progression (TTP) and overall survival (OS) in women who use tamoxifen for metastatic breast cancer (MBC) was examined.

Methods:

We selected patients treated with tamoxifen (40 mg per day) for hormone receptor-positive MBC from whom a blood sample for pharmacogenetic analysis (CYP2D6*3, *4, *5, *6, *10 and *41) was available. Patient charts (n=102) were reviewed to assess TTP and OS, and to determine whether CYP2D6 inhibitors were prescribed during tamoxifen treatment.

Results:

OS was significantly shorter in patients with a poor CYP2D6 metaboliser phenotype, compared with extensive metabolisers (HR=2.09; P=0.034; 95% CI: 1.06–4.12). Co-administration of CYP2D6 inhibitors alone was also associated with a worse OS (HR=3.55; P=0.002; 95% CI: 1.59–7.96) and TTP (HR=2.97; P=0.008; 95% CI: 1.33–6.67) compared with patients without CYP2D6 inhibitors.

Conclusion:

CYP2D6 phenotype is an important predictor of treatment outcome in women who are receiving tamoxifen for MBC. Co-administration of CYP2D6 inhibitors worsens treatment outcome of tamoxifen and should therefore be handled with care.     

Impact of CYP2D6*10 on recurrence-free survival in breast cancer patients receiving adjuvant tamoxifen therapy

The clinical outcomes of breast cancer patients treated with tamoxifen may be influenced by the activity of cytochrome P450 2D6 (CYP2D6) enzyme because tamixifen is metabolized by CYP2D6 to its active forms of antiestrogenic metabolite, 4-hydroxytamoxifen and endoxifen. We investigated the predictive value of the CYP2D6 * 10 allele, which decreased CYP2D6 activity, for clinical outcomes of patients that received adjuvant tamoxifen monotherapy after surgical operation on breast cancer. Among 67 patients examined, those homozygous for the CYP2D6 * 10 alleles revealed a significantly higher incidence of recurrence within 10 years after the operation ( P =  0.0057; odds ratio, 16.63; 95% confidence interval, 1.75–158.12), compared with those homozygous for the wild-type CYP2D6 * 1 alleles. The elevated risk of recurrence seemed to be dependent on the number of CYP2D6 * 10 alleles ( P =  0.0031 for trend). Cox proportional hazard analysis demonstrated that the CYP2D6 genotype and tumor size were independent factors affecting recurrence-free survival. Patients with the CYP2D6 * 10/ * 10 genotype showed a significantly shorter recurrence-free survival period ( P =  0.036; adjusted hazard ratio, 10.04; 95% confidence interval, 1.17–86.27) compared to patients with CYP2D6 * 1/ * 1 after adjustment of other prognosis factors. The present study suggests that the CYP2D6 genotype should be considered when selecting adjuvant hormonal therapy for breast cancer patients. ( Cancer Sci 2008; 99: 995–999)     

CYP2D6 genotype in relation to tamoxifen efficacy in a Dutch cohort of the tamoxifen exemestane adjuvant multinational (TEAM) trial

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. Postmenopausal early breast cancer patients who were randomized to receive tamoxifen, followed by exemestane in a large randomized controlled trial were genotyped for five CYP2D6 alleles. CYP2D6 genotypes and phenotypes were related to disease-free survival during tamoxifen use (DFS-t) in 731 patients. By analyzing microsatellites flanking the CYP2D6 gene, patients whose genotyping results were potentially affected by LOH were excluded. In addition, exploratory analyses on 24 genetic variants of other metabolic enzymes and the estrogen receptor were performed. For the CYP2D6 analysis, only 2.3 % of the samples were excluded, because influence of LOH could not be ruled out. No association was found between the CYP2D6 genotype or predicted phenotype and DFS-t (poor vs. extensive metabolizers: unadjusted hazard ratio 1.33, 95 % CI 0.52–3.43; P = 0.55). DFS-t was associated with UGT2B15*2 (Vt/Vt + Wt/Vt vs. Wt/Wt: adjusted hazard ratio 0.47, 95 % CI 0.25–0.89; P = 0.019) and the estrogen receptor-1 polymorphism ESR1 PvuII (gene–dose effect: adjusted hazard ratio 1.63, 95 % CI 1.04–2.54; P = 0.033). In postmenopausal early breast cancer patients treated with adjuvant tamoxifen followed by exemestane neither CYP2D6 genotype nor phenotype did affect 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. Polymorphisms in the estrogen receptor-1 and UGT2B15 may be associated with tamoxifen efficacy, but these findings need replication.     

The impact of cytochrome P450 2D6 metabolism in women receiving adjuvant tamoxifen

BACKGROUND: Tamoxifen is biotransformed to the potent anti-estrogen, endoxifen, by the cytochrome P450 (CYP) 2D6 enzyme. CYP2D6 genetic variation and inhibitors of the enzyme markedly reduce endoxifen plasma concentrations in tamoxifen-treated patients. Using a North Central Cancer Treatment Group adjuvant tamoxifen trial, we performed a comprehensive evaluation of CYP2D6 metabolism by assessing the combined effect of genetic variation and inhibition of the enzyme system on breast cancer recurrence and death. METHODS: Medical records were reviewed at each randomizing site to determine whether CYP2D6 inhibitors were co-prescribed with tamoxifen. Extensive metabolizers were defined as patients without a *4 allele (i.e., wt/wt) who were not co-prescribed a CYP2D6 inhibitor. Patients with decreased CYP2D6 metabolism were classified as intermediate or poor metabolizers (PM) based on the presence of one or two CYP2D6*4 alleles or the co-administration of a moderate or potent CYP2D6 inhibitor. The association between CYP2D6 metabolism and clinical outcome was assessed using Cox modeling. RESULTS: Medication history was available in 225/256 eligible patients and CYP2D6*4 genotype in 190 patients. Thirteen patients (6%) were co-prescribed a CYP2D6 inhibitor [potent (n = 3), moderate (n = 10)], resulting in the following CYP2D6 metabolism: extensive (n = 115) and decreased (n = 65). In the multivariate analysis, patients with decreased metabolism had significantly shorter time to recurrence (p = 0.034; adj HR = 1.91; 95% CI 1.05-3.45) and worse relapse-free survival (RFS) (p = 0.017; adj HR = 1.74; 1.10-2.74); relative to patients with extensive metabolism. Cox' modeling demonstrated that compared to extensive metabolizers, PM had the most significant risk of breast cancer relapse (HR 3.12, p = 0.007). CONCLUSION: CYP2D6 metabolism, as measured by genetic variation and enzyme inhibition, is an independent predictor of breast cancer outcome in post-menopausal women receiving tamoxifen for early breast cancer. Determination of CYP2D6 genotype may be of value in selecting adjuvant hormonal therapy and it appears CYP2D6 inhibitors should be avoided in tamoxifen-treated women.     

Concurrent use of tamoxifen with CYP2D6 inhibitors and the risk of breast cancer recurrence

Concurrent use of tamoxifen and cytochrome P450 2D6 (CYP2D6) inhibitors, such as selective serotonin reuptake inhibitors, has been shown to decrease plasma concentrations of tamoxifen metabolites. However, it is still unclear whether such concurrent use affects tamoxifen’s effectiveness. Thus, the objective of this study is to determine whether concurrent use of tamoxifen with CYP2D6 inhibitors increases the risk of recurrence in patients newly diagnosed with breast cancer. We conducted a nested case–control analysis within a population-based cohort from the UK General Practice Research Database. The cohort included women with a first-ever diagnosis of breast cancer who were prescribed tamoxifen between January 1, 1998 and June 30, 2008. Cases consisted of all patients with a breast cancer recurrence occurring during follow-up. Up to ten controls were matched to each case on year of birth, date of cohort entry, and duration of follow-up. Conditional logistic regression was used to estimate rate ratios (RR) of breast cancer recurrence in patients who concurrently used tamoxifen with CYP2D6 inhibitors, compared to patients who only used tamoxifen. The cohort included 9,209 incident users of tamoxifen, of whom 807 were diagnosed with a breast cancer recurrence. Concurrent use was not associated with an increased incidence of breast cancer recurrence (adjusted RR 1.07, 95% 0.88, 1.30). Type and strength of CYP2D6 inhibitors, as well as duration of concurrent use did not affect breast cancer recurrence. These results remained consistent after performing sensitivity analyses. The results of this large population-based study indicate that concurrent use of tamoxifen with CYP2D6 inhibitors does not increase the risk of recurrence.     

Optimal timing of adjuvant treatment in patients with early breast cancer

It is well established that adjuvant treatment reduces mortality after early breast cancer. However, the optimal timing of adjuvant treatment is not well described. To determine the optimal timing of adjuvant treatment, 402 breast cancer patients who received adjuvant treatment at Ankara Oncology Research and Training Hospital between January 1995 and August 2002 were evaluated retrospectively. Three hundred and fifty-seven (88.8%) patients received adjuvant chemotherapy, 204 (50.7%) of these patients received only adjuvant chemotherapy and 153 (38%) patients received tamoxifen following chemotherapy. Remaining 45 (11.2%) patients received only adjuvant tamoxifen. The median time to start adjuvant treatment after surgery was day 21 (range, days 4 to days 258), and the median follow-up was 50 months (range, 6–105 months). The patients were divided into 5 groups according to starting time of chemotherapy (shorter than 14 days, between days 15–29, between days 30–44, between days 45.?59 and more than 59 days). Overall survival (OS) and disease-free survival (DFS) were not shown significantly different between for 5 groups (P > 0.05). Secondly, patients were divided into two groups as starting adjuvant treatment equal to or shorter than 44 days and longer than 44 days (n = 344, 85.6% and vs. n = 58, 14.4%, respectively). OS was significantly better in patients who started to receive adjuvant treatment within 44 days after surgery compared to patients who received adjuvant treatment after 44 days (92 vs. 83.3%, P = 0.03) for 5 years, but DFS was not significantly different between two groups (83.4 vs. 82.2%, P > 0.05). According to our study, adjuvant treatment of breast cancer should be initiated earlier after surgery.