Standard Tamoxifen Research Articles

Artonin E and Structural Analogs from Artocarpus Species Abrogates Estrogen Receptor Signaling in Breast Cancer.

The increasing rate of mortality ensued from breast cancer has encouraged research into safer and efficient therapy. The human Estrogen receptor α has been implicated in the majority of reported breast cancer cases. Molecular docking employing Glide, Schrodinger suite 2015, was used to study the binding affinities of small molecules from the Artocarpus species after their drug-like properties were ascertained. The structure of the ligand-binding domain of human Estrogen receptor α was retrieved from Protein Data Bank while the structures of compounds were collected from PubChem database. The binding interactions of the studied compounds were reported as well as their glide scores. The best glide scored ligand, was Artonin E with a score of −12.72 Kcal when compared to other studied phytomolecules and it evoked growth inhibition of an estrogen receptor positive breast cancer cells in submicromolar concentration (3.8–6.9 µM) in comparison to a reference standard Tamoxifen (18.9–24.1 µM) within the tested time point (24–72 h). The studied ligands, which had good interactions with the target receptor, were also drug-like when compared with 95% of orally available drugs with the exception of Artoelastin, whose predicted physicochemical properties rendered it less drug-like. The in silico physicochemical properties, docking interactions and growth inhibition of the best glide scorer are indications of the anti-breast cancer relevance of the studied molecules.

Are SOFT and TEXT results practice changing and how?

Optimal adjuvant endocrine therapy for premenopausal women with hormone-receptor positive breast cancer has long been debated. In particular, the role of ovarian function suppression in addition to standard tamoxifen divided oncologists worldwide, and more recently, the role of aromatase inhibitors as an alternative to tamoxifen in the setting of ovarian suppression became a key question.In 2014, the long awaited results of the International Breast Cancer Study Group (IBCSG) led randomized, phase 3 trials, Suppression of Ovarian Function Trial (SOFT) and Tamoxifen and Exemestane Trial (TEXT), provided additional evidence to inform the discussion.The interpretation of the SOFT and TEXT trial data can facilitate better selection of appropriate endocrine therapy according to individual disease characteristics, recognizing the complexity of the puzzle, which is still not complete.

Abstract P5-15-04: Zoledronic acid combined with adjuvant tamoxifen with or without ovarian function suppression in premenopausal early breast cancer patients

Abstract Background: Bisphosphonates can delay the onset and reduce the risk of skeletal related events in patients with bone metastatic breast cancer; it can prevent and controlcancer treatment-induced bone loss. Zoledronic acid (ZOL) plus adjuvant endocrine therapy significantly improved disease free survival. The aim of the study is to evaluate the benefits of ZOL combined with adjuvant therapy in premenopausal early breast cancer patients. Patients and methods: Patients were premenopausal females who had undergone primary surgery for stage I, II ER +ve and/or PR +ve breast cancer with < 10 positive lymph nodes. All 300 patients were scheduled for standard tamoxifen 20mg/day for five years plus goserelin 3.6 mg every 28 days and were randomized to ZOL 4mg every 6 months for 3 years (group A) and without ZOL (group B). The primary end points were toxicity and disease-free survival (DFS), while overall survival (OS) was the secondary end point. Results: Between April 2005 and March 2012, 300 patients were enrolled, the median follow up duration was 98.4 months (range 14-120 months), adding ZOL to endocrine therapy strongly suggests improved DFS versus endocrine therapy alone (90% versus 85% for an absolute increase of 5%). There were fewer disease recurrences in the ZOL group versus no ZOL group (12% vs. 16%) with the greatest reductions in the loco-regional recurrence (3% vs. 5%), distant metastasis (6% vs. 7%) and bone metastasis (3% vs. 5%). Conclusion: ZOL with adjuvant endocrine therapy were generally well tolerated with no reports of renal failure or osteonecrosis of the jaw. So, a twice yearly ZOL enhanced the efficacy of adjuvant endocrine treatment, and this benefit is maintained for long time. Citation Format: El-Ibrashi MM, El-Sadda WM, Abdel-Halim II, Elashri MS. Zoledronic acid combined with adjuvant tamoxifen with or without ovarian function suppression in premenopausal early breast cancer patients. [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 P5-15-04.

Merkel Cell Polyomavirus Small T Antigen Induces Cancer and Embryonic Merkel Cell Proliferation in a Transgenic Mouse Model.

Merkel cell polyomavirus (MCV) causes the majority of human Merkel cell carcinomas (MCC) and encodes a small T (sT) antigen that transforms immortalized rodent fibroblasts in vitro. To develop a mouse model for MCV sT-induced carcinogenesis, we generated transgenic mice with a flox-stop-flox MCV sT sequence homologously recombined at the ROSA locus (ROSA sT), allowing Cre-mediated, conditional MCV sT expression. Standard tamoxifen (TMX) administration to adult Ubc CreERT2; ROSA sT mice, in which Cre is ubiquitously expressed, resulted in MCV sT expression in multiple organs that was uniformly lethal within 5 days. Conversely, most adult Ubc CreERT2; ROSA sT mice survived low-dose tamoxifen administration but developed ear lobe dermal hyperkeratosis and hypergranulosis. Simultaneous MCV sT expression and conditional homozygous p53 deletion generated multi-focal, poorly-differentiated, highly anaplastic tumors in the spleens and livers of mice after 60 days of TMX treatment. Mouse embryonic fibroblasts from these mice induced to express MCV sT exhibited anchorage-independent cell growth. To examine Merkel cell pathology, MCV sT expression was also induced during mid-embryogenesis in Merkel cells of Atoh1 CreERT2/+; ROSA sT mice, which lead to significantly increased Merkel cell numbers in touch domes at late embryonic ages that normalized postnatally. Tamoxifen administration to adult Atoh1 CreERT2/+; ROSA sT and Atoh1 CreERT2/+; ROSA sT; p53f lox/flox mice had no effects on Merkel cell numbers and did not induce tumor formation. Taken together, these results show that MCV sT stimulates progenitor Merkel cell proliferation in embryonic mice and is a bona fide viral oncoprotein that induces full cancer cell transformation in the p53-null setting.

Boronic prodrug of 4-hydroxytamoxifen is more efficacious than tamoxifen with enhanced bioavailability independent of CYP2D6 status.

BackgroundPoor initial response to tamoxifen due to CYP2D6 polymorphism and adverse side effects are two clinical challenges in tamoxifen therapy. We report the development and preclinical testing of a boronic prodrug to orally deliver 4-OHT at therapeutically effective concentrations but at a fraction of the standard tamoxifen dose.MethodsA mouse xenograft tumor model was used to investigate the efficacy of ZB497 in comparison with tamoxifen. Pharmacokinetic studies were conducted to evaluate the metabolism and bioavailability of the drug in mice. Drug and metabolites distribution in xenograft tumor tissues was determined by high performance liquid chromatography-tandem mass spectrometry.ResultsThe boronic prodrug, ZB497, can not only be efficiently converted to 4-OHT in mice, but also afforded over 30 fold higher plasma concentrations of 4-OHT than in mice given either the same dose of 4-OHT or tamoxifen. Further, ZB497 was more effective than tamoxifen at lowered dosage in inhibiting the growth of xenograft tumors in mice. Consistent with these observations, ZB497 treated mice accumulated over 6 times higher total drug concentrations than tamoxifen treated mice.ConclusionsOur study demonstrates that ZB497 effectively delivers a markedly increased plasma concentration of 4-OHT in mice. The boronic prodrug was shown to have far superior bioavailability of 4-OHT compared to tamoxifen or 4-OHT administration as measured by the area under the plasma concentration time curve (AUC), plasma peak concentrations, and drug accumulation in tumor tissues. Further, ZB497 proves to be a more efficacious hormone therapy than tamoxifen administered at a reduced dose in mice.

Anticancer activity and apoptosis inducing effect of methanolic extract of <i>Cordia dichotoma</i> against human cancer cell line

MTT assay and DAPI staining test were performed to evaluate anticancer potential and to assess apoptosis inducing effect of methanolic extract of Cordia dichotoma leaves (MECD) against human cervical cancer cell line (HeLa). Changes in MMP and intracellular ROS level were also assessed by JC-1 and DCFH-DA staining. Total phenolic contents were determined by colorimetric principle. Levels of statistical significance were determined by one-way analysis of variance followed by Dunnett’s posttest. Results showed that MECD with obtained IC 50 of 202 µg/mL inhibited in vitro proliferation of human cervical cancer cells and induced apoptosis indicating its promising anticancer activity as compared to the standard tamoxifen with obtained IC 50 of 48 µg/mL. Total phenolic contents was found to be 176.5 mg GAE/g dried extract. It was concluded that MECD possess promising anticancer activity and induce apoptosis.

Abstract 4631: Pharmacokinetics and in vivo metabolism of Z-endoxifen: Results from two phase I studies in women with ER+ breast cancer, gynecologic malignancies and desmoids

Abstract Background: Breast cancer recurrence has been shown to differ based upon CYP2D6 genotype and endoxifen (Endx) exposure following treatment with tamoxifen (TAM) in the adjuvant setting. The average Endx Css is 29 nM (range, 2-80 nM) in TAM treated patients at a dose of 20 mg/day. Administration of Endx itself to patients is predicted to provide adequate, consistent, active drug levels in all treated patients, resulting in clinical benefit. As part of two phase 1 trials of oral Endx to determine the safety, tolerability, and MTD, we characterized the pharmacokinetics and in vivo metabolism of Endx. Methods: Patients were given escalating daily oral doses of Endx (28 day cycle) over the dose range of 20 - 160 mg/day in Phase I trials at the Mayo Clinic and NCI. Pharmacokinetics sampling was performed on days 1, 7, 14 and 28, and prior to subsequent cycles. Endx plasma concentrations and metabolite profiles were determined by HPLC and LC/MS/MS. Results: 44 patients with ECOG PS 0-1 have been enrolled to date encompassing 8 dose levels in the Mayo (25 women with AI refractory MBC; median age 58 yrs, range 41-83 yrs) and NCI (19 women with ovary (9), breast (4), desmoid (2), fallopian tube (2), endometrial cancer (2); median age 64 yrs, range 43-75 yrs) studies. Day 1 Endx peak concentrations (Cmax) were reached 4h after the Endx oral dose and mean values of Cmax, C24h, and AUC0-24h increased in proportion to dose. Css was achieved on day 7 and 3.5-fold accumulation (t1/2= 50.5 h) was observed on day 28. At the starting dose ( 20 mg/day) and highest dose level (160 mg/day), Endx Css values of 146 ng/ml (390 nM) and 1950 ng/ml (5200 nM), respectively, were achieved and maintained throughout the 28-day treatment. Endx Css values remained unchanged following continuous dosing for 8-10 months. The mean apparent steady-state clearance was 6.2 L/h. We also characterized the Endx metabolite profile in patient plasma and urine. Metabolites detected in plasma include nor-Endx, N-hydroxy-Endx, Endx-catechol, methoxy-Endx catechol, and Endx-glucuronide, and appear in amounts much lower compared to Endx. Like the parent drug, metabolites accumulated in plasma over the 28-day cycle. Characterization of the pharmacokinetics of Nor-Endx, a putative aromatase inhibitor, is ongoing and will be presented. Conclusion: In these ongoing Phase I studies, daily administration of Endx is well tolerated with Css consistently above those obtained following administration of standard dose tamoxifen. In the Mayo study, expansion at 20 and 100 mg/day has commenced to perform translational studies and further characterize Endx PK. In the NCI study, dose escalation continues to establish the maximum tolerated dose. Supported in part by R01CA 133049, U01 CA69912, P30CA 15083, P50CA 116201 and NCI Contracts CM52206 and HHSN261201100014C. Citation Format: Joel M. Reid, Matthew P. Goetz, Shivaani Kumar, Renee M. McGovern, Sarah A. Buhrow, Stephanie L. Safgren, Vera J. Suman, Travis J. Docktor, Charles Erlichman, Howard Streicher, James H. Doroshow, Jerry Collins, Matthew M. Ames. Pharmacokinetics and in vivo metabolism of Z-endoxifen: Results from two phase I studies in women with ER+ breast cancer, gynecologic malignancies and desmoids. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4631. doi:10.1158/1538-7445.AM2014-4631

Synthesis, in-vitro screening, and docking analysis of novel pyrrolidine and piperidine-substituted ethoxy chalcone as anticancer agents

A series of novel-substituted chalcone analogs were synthesized and evaluated for antiproliferative activity against estrogen receptor-positive MCF-7 breast cancer cell lines. Among the synthesized derivatives 4a, 5a, 5b, 5c, 5e, 5′a, and 5′d show good antiproliferative activity as compared to standard tamoxifen. The study highlighted the advantage of introducing the amine side chain pharmacophore in substituted chalcone enhances the anticancer potential. The study also suggests that these analogs can serve as better therapeutic agents against breast cancer and can provide starting point for building more potent analogs in future. The binding mechanism and ADME properties of target compounds were analysed using Schrodinger software.

Adjusting the dose of tamoxifen in patients with early breast cancer and CYP2D6 poor metabolizer phenotype

BackgroundCYP2D6 is a key enzyme in tamoxifen metabolism, transforming it into its main active metabolite, endoxifen. Poor CYP2D6 metabolizers (PM) have lower endoxifen plasma concentrations and possibly benefit less from treatment with tamoxifen. We evaluated tamoxifen dose adjustment in CYP2D6 PM patients in order to obtain plasma concentrations of endoxifen comparable to patients with extensive CYP2D6 metabolism (EM). Patients and methodsComprehensive CYP2D6 genotyping and plasma tamoxifen metabolite concentrations were performed among 249 breast cancer patients in adjuvant treatment with tamoxifen. Tamoxifen dose was increased in PM patients to 40 mg and to 60 mg daily for a 4-month period each, repeating tamoxifen metabolite measurements on completion of each dose increase. We compared the endoxifen levels between EM and PM patients, and among the PM patients at each dose level of tamoxifen (20, 40 and 60 mg). ResultsEleven PM patients (4.7%) were identified. The mean baseline endoxifen concentration in EM patients (11.30 ng/ml) was higher compared to the PM patients (2.33 ng/ml; p < 0.001). In relation to the 20 mg dose, increasing the tamoxifen dose to 40 and 60 mg in PM patients significantly raised the endoxifen concentration to 8.38 ng/ml (OR 3.59; p = 0.013) and to 9.30 ng/ml (OR 3.99; p = 0.007), respectively. These concentrations were comparable to those observed in EM patients receiving 20 mg of tamoxifen (p = 0.13 and p = 0.64, respectively). ConclusionIn CYP2D6 PM patients, increasing the standard tamoxifen dose two-fold or three-fold raises endoxifen concentrations to levels similar to those of patients with EM phenotype.

Expression profiling of breast cancer patients treated with tamoxifen: prognostic or predictive significance

Approximately 70% of breast cancers are estrogen receptor (ER) positive, and interfering with estrogen action with tamoxifen has been the treatment of choice for ER-positive breast cancer patients. However, about a third of patients treated with tamoxifen will experience a recurrence of cancer. The expression analysis of selected genes involved in tamoxifen/estrogen and receptor tyrosine kinase signaling pathways can help to further decipher mechanisms of recurrence in ER+ tumors and contribute to the development of prognostic and possibly predictive biomarkers. We selected seven genes (ESR1, CCND1, MYC, HER2, AKT1, AIB1 and NCOR1), which are components of these pathways. A case-control study was designed. All patients in the control group had received standard adjuvant tamoxifen treatment for 5 years without any evidence of recurrence. Patients in the case group had experienced an early recurrence of cancer while receiving tamoxifen treatment. Expression levels of selected genes in both groups were compared. Expression levels of CCND1 (p < 0.001), HER2 (p < 0.001), AKT1 (p = 0.038) and AIB1 (p = 0.004) were significantly higher in recurrent tumors compared to non-recurrent tumors, while expression levels of NCOR1 (p < 0.001) were significantly lower in recurrent tumors. In multivariable analysis, CCND1 (p < 0.001), HER2 (p = 0.003), AIB1 (p = 0.036) and NCOR1 (p = 0.002) remained significant predictors of recurrence. Expression levels of CCND1, HER2, AIB1 and NCOR1 were detected as independent predictors of recurrence in this cohort of tamoxifen-treated patients. Further work should be done to validate the predictive value of this gene profile for tamoxifen response.

Therapeutic effect of Ananus comosus peel on breast cancer induced by 7, 12- dimethylbenz(α)anthracene

Ananus comosus , has demonstrated a wide variety of biological activities which make it a good plant source for the treatment of many oxidative stress mediated diseases. The present study was aimed to evaluate therapeutic potential by assaying the activities of liver marker and lysosomal enzymes in 7, 12 dimethylbenz(α)anthracene induced mammary cancer bearing rats. Animals were divided into five groups of six numbers each. Group 1 served as control, group 2 induced mammary carcinogenesis, group 3 and 4 were treated with plant extract and tamoxifen and group 5 served as animals treated with plant extract alone. All the animals were sacrificed after 30 days treatment, serum and mammary tissue are used for the analysis of liver marker and lysosomal marker enzymes using standard protocols. The rats were induced with mammary cancer by DMBA showed altered the levels of liver markers and lysosomal marker enzymes in serum and mammary tissue. On the other hand, oral administrations of ethanolic extract of Ananus comosus peel and standard drug tamoxifen to mammary cancer bearing rats for 30 days, those levels were brought back to near normal. The histology of mammary tissues inevitably supports the biochemical alterations and this was attributed due to the interaction of Ananus comosus peel through the induction or inhibition of metabolism and also the modulating property in the marker and lysosomal enzymes.

Abstract P1-13-10: Long-term pathologic findings in the female genital tract after completion of tamoxifen therapy for premenopausal breast cancer

Abstract Introduction: Tamoxifen (TMX) remains the main compound for adjuvant hormone therapy in premenopausal breast cancer patients. Potential uterine carcinogenicity and other effects on the female genital tract are recognized risks for TMX, but further studies with longer follow-up are needed for the subpopulation of young premenopausal patients, with prolonged life span. Material and Methods: Retrospective analysis of the female genital tract pathologic findings found in a population of premenopausal breast cancer patients who completed at least five years of adjuvant TMX (20 mg/d) in a single center with a minimum follow-up of 10 years since the start of TMX (1985-June 2003). Periodic gynecologic exams were offered to all the patients and biopsies were performed at the discretion of the reference gynecologists. Pathologic reports from biopsies and surgical specimens were retrieved from the pathology databases of our health system. Menopausal status was defined at diagnosis according to National Comprehensive Cancer Network´s standard criteria. This retrospective study was approved by our local ethics committee. Results: 386 patients (p.) fulfilled inclusion criteria and were searched for data analysis. Median age at the start of TMX: 45 years (23-57). Median follow-up: 14.1 years (10.0-27.5). Further adjuvant hormone therapies were used in 94/386 p. (79 sequential aromatase inhibitors, 15 luteinizing hormone-releasing analogues).11 p. received further adjuvant TMX, mainly within the ATLAS trial, up to 10 years. Hysterectomies during the period of TMX therapy were performed in 24/386 p. Events in the population (all completed the programmed TMX adjuvant therapy) were as follows: 17 locoregional relapses, 37 systemic relapses, 18 contralateral breast cancer, 24 second neoplasms (3 pancreas, 1 endocrine pancreas, 4 melanoma, 4 colon, 3 sarcoma, 2 uterine, 1 ovary, 1 kidney, 1 tongue, 1 thyroid, 1 bladder, 1 lymphoma, 1 leukemia, 1 thyroid). Pathologic findings in the female genital tract after the end of tamoxifen were reported as follows: endometrial and cervical polyps (56), endometrial atrophy (16), endometrial hyperplasia (9), uterine leiomyoma (9), superficial and/or insufficient uterine samples (30), ovarian cysts (9), endometriosis (3), endometritis (1), chronic cervicitis (3), metaplasia (10), adenomyosis (3) vaginal leiomyoma (1), vulvar folliculitis (1), vaginal infiltration from metastatic breast cancer (1), ovarian fibroma (1), ovarian teratoma (1), ovarian metastases from breast cancer (1), vaginal papilloma (1), vaginal polyp (2), vulvar cyst (2),. Endometrial cancer was found in 2/386 p. One of these two patients had a deleterious BRCA2 mutation. Conclusions: The burden of pathologic complications in the female genital tract and endometrial cancer is regarded as low in initially premenopausal breast cancer patients who completed standard adjuvant tamoxifen, even after long follow-up. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-10.

Adjuvant hormonal therapy in young breast cancer patients

1 ISSN 1758-1923 10.2217/BMT.13.67 © 2014 Future Medicine Ltd Breast Cancer Manage. (2014) 3(1), 1–4 Breast cancer arising at a young age is a complex condition, requiring multidisciplinary and personalized approaches to manage the specific issues related not only to optimal adjuvant treatments, but also to other important quality-of-life issues, such as bone health, premature menopause, fertility preservation and long-term cognitive function [1]. Approximately 5% of women with breast cancer are diagnosed before the age of 40 years, but the incidence appears to be on the rise [101]. In the adjuvant setting, 5 years of tamoxifen treatment is considered the current standard of care in managing young women with an endocrine-sensitive disease. Based on the meta-analysis of the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), 5 years of tamoxifen significantly reduced breast cancer mortality throughout the first 15 years, with a greater effect when tamoxifen was given for 5 years compared with 2 years [2]. Nevertheless, in the past decade several questions were raised and remain unanswered in the field of adjuvant endocrine treatment of young breast cancer patients, including the optimal duration of adjuvant endocrine therapy, the addition of luteinizing hormone-releasing hormone analogs (LHRHa) to standard tamoxifen and its duration, and the use of aromatase inhibitors. The first evidence regarding the possible benefit of extending adjuvant endocrine therapy beyond 5 years of tamoxifen was based on the results of the MA.17 trial, where patients were randomized to receive or not receive letrozole following the completion of tamoxifen treatment. The main analysis indicated that women originally assigned to receive letrozole had a 32% reduction in the risk of relapse [3]. A subgroup analysis suggested that the benefit in terms of disease-free survival was greater in premenopausal women at the time of initial diagnosis than in postmenopausal patients [3]. More recently, the results of two important clinical trials that assessed the possible benefit of extending adjuvant tamoxifen up to 10 years instead of stopping it after 5 years became available [4,5]. The ATLAS trial included a total of 12,894 patients: 2482 (19%) were younger than 45 years at diagnosis and 1058 (8%) were known to be premenopausal at the

Cardiac fibrosis in mice expressing an inducible myocardial-specific Cre driver

SUMMARYTamoxifen-inducible Cre-mediated manipulation of animal genomes has achieved wide acceptance over the last decade, with numerous important studies heavily relying on this technique. Recently, a number of groups have reported transient complications of using this protocol in the heart. In the present study we observed a previously unreported focal fibrosis and depressed left-ventricular function in tamoxifen-treated αMHC-MerCreMer-positive animals in a Tβ4shRNAflox × αMHC-MerCreMer cross at 6–7 weeks following standard tamoxifen treatment, regardless of the presence of the floxed transgene. The phenotype was reproduced by treating mice from the original αMHC-MerCreMer strain with tamoxifen. In the acute phase after tamoxifen treatment, cell infiltration into the myocardium was accompanied by increased expression of pro-inflammatory cytokines (IL-1β, IL-6, TNFα, IFNγ, Ccl2) and markers of hypertrophy (ANF, BNP, Col3a1). These observations highlight the requirement for including tamoxifen-treated MerCreMer littermate controls to avert misinterpretation of conditional mutant phenotypes. A survey of the field as well as the protocols presented here suggests that controlling the parameters of tamoxifen delivery is important in avoiding the chronic MerCreMer-mediated cardiac phenotype reported here.

CYP2D6 genotype and adverse effects as indicators of plasma endoxifen in breast cancer patients taking tamoxifen.

550 Background: Tamoxifen is a prodrug. Its principal active metabolite endoxifen is a product of cytochrome P450 2D6 (CYP2D6) metabolism. The CYP2D6 gene is highly polymorphic with a number of relatively common reduced function alleles. The aim of this study was to determine whether plasma endoxifen levels were reflected by CYP2D6 genotype or adverse effects in individuals taking tamoxifen. Methods: Plasma endoxifen was measured by High Performance Liquid Chromatography / Mass Spectroscopy in 90 breast cancer patients taking 20mg tamoxifen per day. Ten CYP2D6 single nucleotide polymorphisms were assessed to designate four putative CYP2D6 functional categories: ultra-rapid (UM), extensive (EM), intermediate (IM) and poor (PM) metabolizers. CYP2D6 inhibitor use and adverse effects were documented. The study was part of an ongoing Australian trial of tamoxifen dose escalation. Results: There was marked variation in plasma endoxifen levels across the cohort (mean 27.6 nM, SD 14.3). Endoxifen levels were significantly associated with metabolizer categories (p&lt;0.001, r= -0.44), but were not distinctive between categories. For example, in the EM category (n=46) endoxifen levels ranged from 3.8-72.2 nM (mean 32.6 nM) with levels in the lowest quartile (3.8-19.7 nM) substantially overlapping the PM category (n=11); 6.1-24.7 nM. Consistent with an impact of non-CYP2D6 genotype related factors on endoxifen levels, endoxifen was significantly lower in 18 patients taking CYP2D6 inhibitor medications (p=0.005). There was no association between endoxifen levels and vasomotor symptoms or other adverse effects of tamoxifen. Conclusions: Endoxifen levels were highly variable in patients taking standard dose tamoxifen, and not predicted by CYP2D6 genotype or adverse effects. Therapeutic monitoring of endoxifen levels may be a useful approach to assess tamoxifen activity.

A multicenter phase II trial of the LH-RH analogue and an aromatase inhibitor combination in premenopausal patients with advanced or recurrent breast cancer refractory to an LH-RH analogue with tamoxifen: JMTO BC08-01.

588 Background: The aim was to provide an endocrine therapy option against advanced (ABC) or recurrent breast cancer (RBC) in premenopausal women. We conducted an exploratory phase II trial in combination with an LH-RH analogue (LH-RHa) and an aromatase inhibitor (AI) to assess the efficacy and tolerability after failure of standard LH-RHa plus tamoxifen (TAM). Methods: Premenopausal patients (pts) with ER+ and/or PgR+ ABC or RBC refractory to LH-RHa + TAM were treated with LH-RHa (goserelin: GOS) and AI (anastrozole: ANA). The primary endpoint was an objective response rate (ORR). Secondary endpoints included progression-free survival (PFS), overall survival (OS), clinical benefit rate (CBR) based on RECIST, and safety assessed using CTCAE ver. 3.0. Pts with only bone legions were assessed using the criteria by Japanese Breast Cancer Society (14th Ed.). Local assessment (CR, PR or long SD of 24 weeks or longer) was confirmed independently by two radiologists. Results: Between September 2008 and November 2010, 37 pts were enrolled at 10 clinical institutions in Japan. Eleven had recurrence either during, or within one year after the end of adjuvant GOS + TAM (including GOS + TAM followed by only TAM). The disease progressed in 26 women during GOS + TAM. Mean age and BMI were 43.5 years and 22.2 kg/m2, respectively. Thirty-five pts (94.6%) were ER+, and 36 pts (97.3%) were HER2- (one with unknown HER2 status). Non-endocrine treatment included chemotherapy (20 pts; 54%) and radiation therapy (13 pts; 35%). The viscera, soft tissue, and bones were treated in 17, 15 and 14 pts, respectively. Pts with both measurable lesions and bone metastasis, measurable lesions only, and only bone metastasis were 21 (57%), 15 (41%) and 1 (2%), respectively. ORR was 18.9% (95%CI: 8.0-35.2%, 1 CR and 6 PR cases), CBR 62.2% (23 pts, 95%CI: 44.8-77.5%), and median PFS was 7.2 months. Eight pts (21.6%) had adverse events, but none resulted in treatment discontinuation. GOS + ANA was well tolerated. Conclusions: LH-RHa (GOS) + ANA can be a subsequent endocrine treatment for premenopausal pts with ABC or RBC after failure of GOS + TAM.

Initialization of adjuvant hormonal treatment for breast cancer

The introduction of aromatase inhibitors (AI) has resulted in practice change approaches in the treatment of early breast cancer. In this paper, we analyze the most relevant studies including the ATAC, BIG 1-98, TEAM, MA-17, NSABP B-33, and ABSCG-6 studies. Postmenopausal patients with hormone receptor-positive early breast cancer should be treated with AI for 5 years. For patients who have been initiated with tamoxifen (TAM), switching to an AI to complete 5 years of treatment is also recommended. The results of the extended adjuvant therapy studies recommend the use of an AI (anastrozole, letrozole, or exemestane) after the completion of standard TAM treatment. With regards to premenopausal women, TAM is the recommended adjuvant hormonal treatment for pre- and perimenopausal women. There is no indication for the use of AI in these subgroups of patients. Finally, determination of CYP 2D6 polymorphisms could be considered when choosing the best adjuvant hormonal treatment option.

Clinical Practice Decisions in Endocrine Therapy

ABSTRACTThe primary goal of systemic adjuvant therapy for breast cancer is to control the risk of local and distant tumor recurrence and thus improve long-term survival. Tamoxifen has been the standard adjuvant endocrine therapy for pre- and postmenopausal women with hormone receptor-positive breast cancer. In estrogen receptor-positive disease, 5 years of tamoxifen reduces the annual breast cancer death rate by 34% irrespective of the use of chemotherapy, age, or other tumor characteristics. Aromatase inhibitors (AIs) can further improve disease-free survival, reducing distant metastases and, in some cases, extending overall survival. Anastrozole and letrozole are approved as upfront adjuvant treatment, anastrozole and exemestane are approved for use in switching strategies after 2–3 years of tamoxifen, and letrozole is approved as extended therapy following the completion of 5 years of standard adjuvant tamoxifen. Choosing the most appropriate adjuvant AI treatment strategy can be a challenge. Original publications and treatment guidelines can help physicians select the optimal adjuvant treatment for individual patients, according to their risk profile.

Comparative review of anastrozole, letrozole and exemestane in the management of early breast cancer

The hormonal therapy of patients with endocrine-sensitive early breast cancer has mainly consisted, for several decades, of the gold standard tamoxifen. The efficacy and favorable toxicity profiles of third-generation aromatase inhibitors (AIs), anastrozole, letrozole and exemestane, in advanced disease led to their development in early breast cancer. Recent results consistently show the superiority of these agents over tamoxifen. Adjuvant trials evaluated AIs using four different therapeutic approaches: (1) Upfront strategy: randomization of newly diagnosed patients: tamoxifen for 5 years versus AI for 5 years. (2) Sequencial strategy: randomization of newly diagnosed patients: tamoxifen (2 – 3 years) followed by AI or the inverse for a total of 5 years versus upfront AI for 5 years. (3) Switch strategy: delayed randomization (or analysis) after 2 – 3 years of tamoxifen (patients free of disease): 2 – 3 years of tamoxifen versus 2 – 3 years of AI (total treatment 5 years). (4) Extended strategy: delayed randomization after 5 years of tamoxifen (patients free of disease): 2 – 5 years of AI versus placebo. Overall, AIs show evidence of superiority over tamoxifen in the adjuvant setting with proven improved efficacy and better toxicity profile. Despite some common characteristics, a body of evidence on AIs indicates some specific differences between the three agents in mechanism of action, pharmacokinetics, efficacy as well as toxicity profiles. Consequently, these hormonal agents may not be considered interchangeable in clinical practice. This review explores available results from AI trials and tries to define their present role in the adjuvant management of postmenopausal patients with breast cancer.

Cytochrome P450 2D6 variants and their association with breast cancer survival.

Abstract Abstract #3089 Background: Cytochrome P450 2D6 (CYP2D6), a phase I drug metabolising enzyme, is involved in the metabolism of up to 25% of all drugs. The CYP2D6 gene is highly polymorphic with over 60 reported variant forms. Many of these have been classified by their effect on drug metaboliser status (poor, intermediate, extensive and ultra). Many variants have low minor allele frequencies (MAF) and metaboliser classification is not always certain. There is conflicting evidence for the potential predictive value of CYP2D6 genotype in patients treated with tamoxifen. In this study we investigate the association of the CYP2D6 gene variants with breast cancer survival in patients treated with tamoxifen.&amp;#x2028; Methods: Invasive breast cancer cases (n=6510), came from SEARCH (East Anglian, UK population-based study), 3155 of these cases had received Tamoxifen therapy. CYP2D6 single nucleotide polymorphisms (SNPs) for genotyping were selected using 2 approaches: (i) Known CYP2D6 functional variants (n=13; MAF&amp;gt;0.01), (ii) tag SNPs , that efficiently tagged all known CYP2D6 common variants on the HapMap database (n=5; MAF&amp;gt;0.05), such that known common SNPs had an rp2 of &amp;gt;0.8 with at least one tagSNP. (Pairwise correlation coefficient (rp2) is a measure of how well one SNP tags another.) The combination of these two approaches aims to capture all known functional variants as well as any, as yet undiscovered variants that may be tagged by the common tagSNPs. Genotyping was carried out using Taqman Assays by Design.&amp;#x2028; Results: Preliminary results, from this ongoing study, indicate that in patients treated with tamoxifen, one rare functional variant (carrier frequency = 0.02), CYP2D6*6, is associated with decreased breast cancer survival (P=0.007; HR=2.03; 95%CI=1.21-3.40), in comparison to patients who have not received hormone therapy (P=0.359; HR=0.52; 95%CI=0.13-2.10). None of the common tagSNPs (MAF&amp;gt;0.05) were associated with differences in survival (at P&amp;lt;/=0.05 level).&amp;#x2028; Conclusion: We conclude that at least one variant of the CYP2D6 gene may affect breast cancer survival in patients treated with tamoxifen. CYP2D6*6 is associated with poor metaboliser status, resulting in impaired tamoxifen metabolism. Consequently genotyping for this CYP2D6 variant may help to determine which patients are unlikely to benefit from standard tamoxifen treatment. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3089.