Clinical perspectives on the utility of aromatase inhibitors for the adjuvant treatment of breast cancer

Adapting and implementing breast cancer follow-up in primary care: protocol for a mixed methods hybrid type 1 effectiveness-implementation cluster randomized study

BACKGROUND

Advances in detection and treatment for breast cancer have led to an increase in the number of individuals managing significant late and long-term treatment effects. Primary care has a role in caring for patients with a history of cancer, yet there is little guidance on how to effectively implement survivorship care evidence into primary care delivery.

METHODS

This protocol describes a multi-phase, mixed methods, stakeholder-driven research process that prioritizes actionable, evidence-based primary care improvements to enhance breast cancer survivorship care by integrating implementation and primary care transformation frameworks: the Exploration, Preparation, Implementation, and Sustainment (EPIS) framework and the Practice Change Model (PCM). Informed by depth interviews and a four round Delphi panel with diverse stakeholders from primary care and oncology, we will implement and evaluate an iterative clinical intervention in a hybrid type 1 effectiveness-implementation cluster randomized design in twenty-six primary care practices. Multi-component implementation strategies will include facilitation, audit and feedback, and learning collaboratives. Ongoing data collection and analysis will be performed to optimize adoption of the intervention. The primary clinical outcome to test effectiveness is comprehensive breast cancer follow-up care. Implementation will be assessed using mixed methods to explore how organizational and contextual variables affect adoption, implementation, and early sustainability for provision of follow-up care, symptom, and risk management activities at six- and 12-months post implementation.

DISCUSSION

Study findings are poised to inform development of scalable, high impact intervention processes to enhance long-term follow-up care for patients with a history of breast cancer in primary care. If successful, next steps would include working with a national primary care practice-based research network to implement a national dissemination study. Actionable activities and processes identified could also be applied to development of organizational and care delivery interventions for follow-up care for other cancer sites.

TRIAL REGISTRATION

Registered with ClinicalTrials.gov on June 2, 2022: NCT05400941.

Influence of Estrogen Treatment on ESR1+ and ESR1- Cells in ER+ Breast Cancer: Insights from Single-Cell Analysis of Patient-Derived Xenograft Models

Simple Summary

The benefit of endocrine therapy is normally observed for cancers with 10% or more of cells positive for ER expression. We compared the gene expression profiles in both ESR1⁺ and ESR1^– cells in ER⁺ tumors following estrogen treatment. Our single-cell RNA sequencing analysis of estrogen-stimulated (SC31) and estrogen-suppressed (GS3) patient-derived xenograft models offered an unprecedented opportunity to address the molecular and functional differences between ESR1⁺ and ESR1^– cells. While estrogen should activate ERα and stimulate ESR1⁺ cells, our findings regarding ESR1^– cells were important, indicating that the proliferation of ESR1^– cells in ER⁺ cancer is also influenced by estrogen. Another valuable finding from our studies was that estrogen also upregulated a tumor-suppressor gene, IL-24, only in GS3. Estrogen increased the percentage of cells expressing IL-24, associated with the estrogen-dependent inhibition of GS3 tumor growth.

Abstract

A 100% ER positivity is not required for an endocrine therapy response. Furthermore, while estrogen typically promotes the progression of hormone-dependent breast cancer via the activation of estrogen receptor (ER)-α, estrogen-induced tumor suppression in ER⁺ breast cancer has been clinically observed. With the success in establishing estrogen-stimulated (SC31) and estrogen-suppressed (GS3) patient-derived xenograft (PDX) models, single-cell RNA sequencing analysis was performed to determine the impact of estrogen on ESR1⁺ and ESR1^– tumor cells. We found that 17β-estradiol (E2)-induced suppression of GS3 transpired through wild-type and unamplified ERα. E2 upregulated the expression of estrogen-dependent genes in both SC31 and GS3; however, E2 induced cell cycle advance in SC31, while it resulted in cell cycle arrest in GS3. Importantly, these gene expression changes occurred in both ESR1⁺ and ESR1^– cells within the same breast tumors, demonstrating for the first time a differential effect of estrogen on ESR1^– cells. E2 also upregulated a tumor-suppressor gene, IL-24, in GS3. The apoptosis gene set was upregulated and the G2M checkpoint gene set was downregulated in most IL-24⁺ cells after E2 treatment. In summary, estrogen affected pathologically defined ER⁺ tumors differently, influencing both ESR1⁺ and ESR1^– cells. Our results also suggest IL-24 to be a potential marker of estrogen-suppressed tumors.

Breast cancer survivorship care beyond local and systemic therapy

Despite persistent inequities in access to care and treatments, advances in combined modality care have led to a steady improvement in outcomes for breast cancer patients across the globe. When estimating the magnitude of clinical benefit of therapies, providers and patients must contend with a multitude of factors that impact treatment decisions and can have long-term effects on quality of life and survival. These include commonly described early toxicities, like aromatase inhibitor-associated musculoskeletal syndrome and neuropathy. But longer-term comorbidities often observed among cancer survivors including weight gain, obesity, infertility, psychological distress, sexual dysfunction, second cancers, bone loss, and body image issues can have lasting effects on quality of life. Equally important, system-level factors such as access to care and resource allocation can have a systemic impact on survival and on the quality of survivorship. Financial toxicity including underemployment can have a lasting impact on patients and caregivers. The resulting disparities in access to treatment can help explain much of the observed variability in outcomes, even within high-income countries like the US. This article revisits some of secondary effects from therapies discussed in a prior 2015 review article, along with other impediments to the optimal delivery of breast cancer care that can affect patients anywhere.

Assessment of the Aromatase Inhibitory Activity of Ma-Huang-Tang (MHT) and Its Active Compounds

Aromatase, a cytochrome P450 enzyme that converts androgens into estrogens, is an important drug target for hormone-dependent diseases. The purpose of this study was to elucidate the aromatase inhibitory effects of Ma-Huang-Tang (MHT), a traditional Korean herbal medicine prescription, and to identify its active ingredients. In this study, the inhibitory effect of MHT on aromatase activity was observed using dibenzylfluorescein (DBF) and KGN cells, and the dose-dependent effect of MHT was verified (IC₅₀ values of 251 μg/mL and 246 μg/mL as determined by the two methods, respectively). Furthermore, among the six herbal medicines that constitute MHT, Ephedrae Herba, Cinnamomi Ramulus, and Glycyrrhizae Radix et Rhizoma showed the most potent inhibition of aromatase activity. Furthermore, upon identification of the active MHT compounds, three markers from Glycyrrhizae Radix et Rhizoma, liquiritin (5), liquiritin apioside (6), and liquiritigenin (7), were verified (IC₅₀ values of 530 μM, 508 μM, and 1.611 mM and 499 μM, 522 μM, and 1.41 mM as determined by the two methods, respectively). In addition, their contents were confirmed to be 15.58, 19.80, and 2.22 mg/g, respectively, by HPLC/DAD analysis. These results indicate that the aromatase inhibitory effect of MHT results from the synergistic action of its active components and that MHT has potential as a preventive agent against aromatase activity.

Zinc Transporters and the Progression of Breast Cancers

Zinc (Zn) is an essential heavy metal utilized in numerous biological processes in mammals, including its recently described role as a signaling mediator. The movement of Zn in and out of cells, across membranes, is regulated by two protein families: the zinc-regulated transporter (ZRT), iron-regulated transporter (IRT)-like protein (ZIP) and the Zn transporter (ZnT) families. ZIPs and ZnTs maintain intracellular Zn homeostasis and control important cellular functions through Zn signaling. Recent studies have highlighted the role of Zn transporters and Zn in disease. ZIP6, 7, and 10 contribute to human breast cancer progression. ZIP6 is associated with breast tumor grade, size, and stage, suggesting that it is a potent driving force toward malignancy; ZIP7 plays an important role in tamoxifen-resistant breast cancer cells, and ZIP10 is involved in invasion and metastasis of breast cancer cells. These Zn transporters are key molecules in the malignant process; thus, understanding Zn transporters will lead to novel diagnostic and therapeutic strategies for breast cancer. This review discusses the emerging functional roles of Zn and Zn transporters in breast cancer.

Breast cancer survivorship: state of the science

PURPOSE

Only recently has breast cancer survivorship earned formal recognition as a research discipline. Complicating survivorship research is the frequent overlap between aging and treatment sequelae. The ACS/ASCO 2016 Breast Cancer Survivorship Care Guideline (Guideline) reflects comprehensive literature review through April 2015, while the jointly sponsored, inaugural Cancer Survivorship Symposium in 2016 (Symposium) reflects ongoing research activity in the area. Together, these platforms provide an opportunity to examine the use of randomized trials and controlled studies in survivorship care research.

METHODS

All 236 citations from the Guideline and all 250 abstracts from the Symposium were reviewed independently by two authors and assigned to prospectively determined categories.

RESULTS

Guideline citations were most frequently reviews (n = 88, 37.3%) and non-randomized, non-controlled studies (n = 51, 21.6%). Thirty-seven (15.7%) randomized trials were cited. Only 9% of Guideline recommendations were based on randomized clinical trial evidence, while 64% were based on evidence level "0" (expert opinion, clinical practice, etc.). Symposium abstracts consisted largely of non-randomized, non-controlled studies (n = 113, 45.2%), with ten completed randomized trials (4%). Few Guideline citations or Symposium abstracts incorporated matched, cancer-free controls.

CONCLUSIONS

Based on the literature underlying the ASCO Guideline as well as a survey of the Cancer Survivorship Symposium abstracts, a significant proportion of the survivorship literature at least through 2015 consisted of non-randomized, non-controlled studies. To optimally address survivorship issues, cancer therapy sequelae need to be distinguished from normal aging in studies incorporating cancer-free controls, and randomized clinical trials are needed to inform intervention strategies.

Stapled BIG3 helical peptide ERAP potentiates anti-tumour activity for breast cancer therapeutics

Estradiol (E2) and the oestrogen receptor-alpha (ERα) signalling pathway play pivotal roles in the proliferative activity of breast cancer cells. Recent findings show that the brefeldin A-inhibited guanine nucleotide-exchange protein 3-prohibitin 2 (BIG3-PHB2) complex plays a crucial role in E2/ERα signalling modulation in breast cancer cells. Moreover, specific inhibition of the BIG3-PHB2 interaction using the ERα activity-regulator synthetic peptide (ERAP: 165–177 amino acids), derived from α-helical BIG3 sequence, resulted in a significant anti-tumour effect. However, the duration of this effect was very short for viable clinical application. We developed the chemically modified ERAP using stapling methods (stapledERAP) to improve the duration of its antitumour effects. The stapledERAP specifically inhibited the BIG3-PHB2 interaction and exhibited long-lasting suppressive activity. Its intracellular localization without the membrane-permeable polyarginine sequence was possible via the formation of a stable α-helix structure by stapling. Tumour bearing-mice treated daily or weekly with stapledERAP effectively prevented the BIG3-PHB2 interaction, leading to complete regression of E2-dependent tumours in vivo. Most importantly, combination of stapledERAP with tamoxifen, fulvestrant, and everolimus caused synergistic inhibitory effects on growth of breast cancer cells. Our findings suggested that the stapled ERAP may be a promising anti-tumour drug to suppress luminal-type breast cancer growth.

Overcoming aromatase inhibitor resistance in breast cancer: possible mechanisms and clinical applications

Estrogen plays crucial roles in the progression of hormone-dependent breast cancers through activation of nuclear estrogen receptor α (ER). Estrogen is produced locally from circulating inactive steroids and adrenal androgens in postmenopausal women. However, conversion by aromatase is a rate-limiting step in intratumoral estrogen production in breast cancer. Aromatase inhibitors (AIs) inhibit the growth of hormone-dependent breast cancers by blocking the conversion of adrenal androgens to estrogen and by unmasking the inhibitory effect of androgens, acting via the androgen receptor (AR). AIs are thus a standard treatment option for postmenopausal hormone-dependent breast cancer. However, although initial use of AIs provides substantial clinical benefit, some breast cancer patients relapse because of the acquisition of AI resistance. A better understanding of the mechanisms of AI resistance may contribute to the development of new therapeutic strategies and aid in the search for new therapeutic targets and agents. We have investigated AI-resistance mechanisms and established six AI-resistant cell lines. Some of them exhibit estrogen depletion-resistance properties via constitutive ER-activation or ER-independent growth signaling. We examined how breast cancer cells can adapt to estrogen depletion and androgen superabundance. Estrogen and estrogenic androgen produced independently from aromatase contributed to cell proliferation in some of these cell lines, while another showed AR-dependent cell proliferation. Based on these findings, currently proposed AI-resistance mechanisms include an aromatase-independent estrogen-producing pathway, estrogen-independent ER function, and ER-independent growth signaling. This review summarizes several hypotheses of AI-resistance mechanisms and discusses how existing or novel therapeutic agents may be applied to treat AI-resistant breast cancers.

Age-related differences in persistence in women with breast cancer treated with tamoxifen or aromatase inhibitors in Germany

AIMS

To study age-related persistence in postmenopausal women with endocrine-responsive breast cancer treated with tamoxifen (TAM) and aromatase inhibitors (AI).

METHODS

Data on 29,245 patients diagnosed with metastatic or non-metastatic breast cancer (BC) and initially treated with TAM or AI between 2004 and 2013 were included. The primary outcome measure was the age-dependent rate of discontinuation of endocrine treatment within 5years after initiation. Discontinuation of therapy was defined as a period of at least 90days without treatment. A multivariate Cox regression model was created to determine the influence of age on the risk of discontinuation. Health insurance type (private/statutory), type of care (gynecological/general), region (West/East Germany), concomitant diagnoses (depression, osteoporosis, and diabetes), and Charlson Comorbidity Score were included as covariates.

RESULTS

The mean ages of the women in the <70 and ≥70 groups were 55.9 (SD: 9.7) and 77.4 (SD: 5.4) years, respectively. Within 5years after treatment initiation, 88.8% of women <70 of age and 82% of women ≥70 years of age had terminated treatment (p-value<0.001). Patients aged ≥70 exhibited a lower risk of treatment discontinuation than patients aged <70 (HR=0.75, 95% CI: 0.66-0.85). Furthermore, gynecological practices, disease management programs, and high Charlson scores increased persistence.

CONCLUSIONS

Overall, the present study indicates that persistence rates are low in both women with BC aged <70 and those aged ≥70 years. We also found that younger women with BC are at a higher risk of treatment discontinuation than older women.

Medication use trajectories of postmenopausal breast cancer survivors and matched cancer-free controls

While adverse medical sequelae are associated with breast cancer therapies, information on breast cancer impact on medication use is limited. Therefore, we compared medication use before and after diagnosis of early stage breast cancer to medication use in matched, cancer-free controls. Of 68,132 Women's Health Initiative participants, 3726 were diagnosed with breast cancer and, after exclusions, in 1731 breast cancer cases, medication use before and >3 years after diagnosis (mean 5.3 ± 2.1 SD) was compared to use in 1731 cancer-free matched controls on similar inventory dates. The medication category number at follow-up inventory was the primary study outcome. Medication category use (n, mean, SD) was comparable at baseline and significantly increased at follow-up in both cases (2.48 ± 1.66 vs. 4.15 ± 2.13, baseline vs follow-up, respectively, P < .0001) and controls (2.44 ± 1.67 vs. 3.95 ± 2.13, respectively, P < .0001), with clinically marginal but statistically significant additional medication category use by cases (0.20 ± 2.40, P < .0001). Tamoxifen users used somewhat more selected medication categories at follow-up assessment (mean 3.40 ± 1.89 vs. 3.21 ± 1.99, respectively, P = 0.05), while aromatase inhibitor users used more medication categories (mean 4.85 ± 2.10 vs. 4.44 ± 1.94, respectively, P = 0.02). No increase in medication category was seen in cases who were not current endocrine therapy users. Breast cancer survivors having only a clinically marginal increase in medication use compared to cancer-free controls. These findings highlight the importance of incorporation of control populations in studies of cancer survivorship.

Xanthohumol suppresses oestrogen-signalling in breast cancer through the inhibition of BIG3-PHB2 interactions

Xanthohumol (XN) is a natural anticancer compound that inhibits the proliferation of oestrogen receptor-α (ERα)-positive breast cancer cells. However, the precise mechanism of the antitumour effects of XN on oestrogen (E2)-dependent cell growth, and especially its direct target molecule(s), remain(s) largely unknown. Here, we focus on whether XN directly binds to the tumour suppressor protein prohibitin 2 (PHB2), forming a novel natural antitumour compound targeting the BIG3-PHB2 complex and acting as a pivotal modulator of E2/ERα signalling in breast cancer cells. XN treatment effectively prevented the BIG3-PHB2 interaction, thereby releasing PHB2 to directly bind to both nuclear- and cytoplasmic ERα. This event led to the complete suppression of the E2-signalling pathways and ERα-positive breast cancer cell growth both in vitro and in vivo, but did not suppress the growth of normal mammary epithelial cells. Our findings suggest that XN may be a promising natural compound to suppress the growth of luminal-type breast cancer.

Discovery of novel aromatase inhibitors using a homogeneous time-resolved fluorescence assay

AIM

Aromatase is an important target for drugs to treat hormone-dependent diseases, including breast cancer. The aim of this study was to develop a homogeneous time-resolved fluorescence (HTRF) aromatase assay suitable for high-throughput screening (HTS).

METHODS

A 384-well aromatase HTRF assay was established, and used to screen about 7000 compounds from a compound library. Anti-proliferation activity of the hit was evaluated using alamarBlue(R) assay in a hormone-dependent breast cancer cell line T47D. Molecular docking was conducted to elucidate the binding mode of the hit using the Discovery Studio program.

RESULTS

The Z' value and signal to background (S/B) ratio were 0.74 and 5.4, respectively. Among the 7000 compounds, 4 hits (XHN22, XHN26, XHN27 and triptoquinone A) were found to inhibit aromatase with IC50 values of 1.60±0.07, 2.76±0.24, 0.81±0.08 and 45.8±11.3 μmol /L, respectively. The hits XHN22, XHN26 and XHN27 shared the same chemical scaffold of 4-imidazolyl quinoline. Moreover, the most potent hit XHN27 at 10 and 50 μmol/L inhibited the proliferation of T47D cells by 45.3% and 35.2%, respectively. The docking study revealed that XHN27 docked within the active site of aromatase and might form a hydrogen bond and had a π-cation interaction with amino acid residues of the protein.

CONCLUSION

XHN27, an imidazolyl quinoline derivative of flavonoid, is a potent aromatase inhibitor with anti-proliferation activity against breast cancer in vitro. The established assay can be used in HTS for discovering novel aromatase inhibitor.

Quality of life in MAP.3 (Mammary Prevention 3): a randomized, placebo-controlled trial evaluating exemestane for prevention of breast cancer

PURPOSE

Exemestane, a steroidal aromatase inhibitor, reduced invasive breast cancer incidence by 65% among 4,560 postmenopausal women randomly assigned to exemestane (25 mg per day) compared with placebo in the National Cancer Institute of Canada (NCIC) Clinical Trials Group MAP.3 (Mammary Prevention 3) trial, but effects on quality of life (QOL) were not fully described.

PATIENTS AND METHODS

Menopause-specific and health-related QOL were assessed by using the four Menopause-Specific Quality of Life Questionnaire (MENQOL) domains and the eight Medical Outcomes Study Short Form Health Survey (SF-36) scales at baseline, 6 months, and yearly thereafter. MENQOL questionnaire completion was high (88% to 98%) in both groups at each follow-up visit. Change scores for each MENQOL and SF-36 scale, calculated at each assessment time relative to baseline, were compared by using the Wilcoxon rank-sum test. Clinically important worsened QOL was defined as a MENQOL change score increase of more than 0.5 (of 8) points and an SF-36 change score decrease of more than 5 (of 100) points from baseline.

RESULTS

Exemestane had small negative effects on women's self-reported vasomotor symptoms, sexual symptoms, and pain, which occurred mainly in the first 6 months to 2 years after random assignment. However, these changes represented only a small excess number of women being given exemestane with clinically important worsening of QOL at one time or another; specifically, 8% more in the vasomotor domain and 4% more each in the sexual domain and for pain. No other between-group differences were observed. Overall, slightly more women in the exemestane arm (32%) than in the placebo arm (28%) discontinued assigned treatment.

CONCLUSION

Exemestane given for prevention has limited negative impact on menopause-specific and health-related QOL in healthy postmenopausal women at risk for breast cancer.

Adherence to endocrine therapy in breast cancer adjuvant and prevention settings

Adherence to oral endocrine therapy in adjuvant breast cancer settings is a substantial clinical problem. To provide current perspective on adherence to oral endocrine therapies, a comprehensive literature review was conducted. In adjuvant trials, endocrine therapy adherence is relatively high with greater adherence for aromatase inhibitors compared with tamoxifen. In contrast, adherence to adjuvant therapy in clinical practice is relatively poor, with only about 50% of women successfully completing 5-year therapy. Importantly, good adherence (>80% use) has been associated with lower recurrence risk. Endocrine therapy adherence in primary breast cancer prevention trials parallels that seen in adjuvant trials. Factors associated with nonadherence include low recurrence risk perception, side effects, age extremes, medication cost, suboptimal patient-physician communication, and lack of social support. Few prospective studies have evaluated interventions designed to improve adherence. Interventions currently proposed reflect inferences from clinical trial procedures in which clinical contacts are commonly greater than in usual practice settings. In conclusion, for optimal breast cancer outcome, adherence to endocrine therapy must improve. Although general recommendations likely to improve adherence can be made based on clinical trial results and preliminary prospective trial findings, research specifically targeting this issue is needed to establish effective intervention strategies.

Possible role of the aromatase-independent steroid metabolism pathways in hormone responsive primary breast cancers

Aromatase inhibitors (AIs) exert antiproliferative effects by reducing local estrogen production from androgens in postmenopausal women with hormone-responsive breast cancer. Previous reports have shown that androgen metabolites generated by the aromatase-independent enzymes, 5α-androstane-3β, 17β-diol (3β-diol), androst-5-ene-3β, and 17β-diol (A-diol), also activate estrogen receptor (ER) α. Estradiol (E2) can also reportedly be generated from estrone sulfate (E1S) pooled in the plasma. Estrogenic steroid-producing aromatase-independent pathways have thus been proposed as a mechanism of AI resistance. However, it is unclear whether these pathways are functional in clinical breast cancer. To investigate this issue, we assessed the transcriptional activities of ER in 45 ER-positive human breast cancers using the adenovirus estrogen-response element-green fluorescent protein assay and mRNA expression levels of the ER target gene, progesterone receptor, as indicators of ex vivo and in vivo ER activity, respectively. We also determined mRNA expression levels of 5α-reductase type 1 (SRD5A1) and 3β-hydroxysteroid dehydrogenase type 1 (3β-HSD type 1; HSD3B1), which produce 3β-diol from androgens, and of steroid sulfatase (STS) and 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD type 1; HSD17B1), which produce E2 or A-diol from E1S or dehydroepiandrosterone sulfate. SRD5A1 and HSD3B1 expression levels were positively correlated with ex vivo and in vivo ER activities. STS and HSD17B1 expression levels were positively correlated with in vivo ER activity alone. Elevated expression levels of these steroid-metabolizing enzymes in association with high in vivo ER activity were particularly notable in postmenopausal patients. Analysis of the expression levels of steroid-metabolizing enzymes revealed positive correlations between SRD5A1 and HSD3B1, and STS and HSD17B1. These findings suggest that the SRD5A1-HSD3B1 as well as the STS-HSD17B pathways, could contributes to ER activation, especially postmenopause. These pathways might function as an alternative estrogenic steroid-producing, aromatase-independent pathways.

Targeted therapy for breast cancer prevention

With a better understanding of the etiology of breast cancer, molecularly targeted drugs have been developed and are being testing for the treatment and prevention of breast cancer. Targeted drugs that inhibit the estrogen receptor (ER) or estrogen-activated pathways include the selective ER modulators (tamoxifen, raloxifene, and lasofoxifene) and aromatase inhibitors (AIs) (anastrozole, letrozole, and exemestane) have been tested in preclinical and clinical studies. Tamoxifen and raloxifene have been shown to reduce the risk of breast cancer and promising results of AIs in breast cancer trials, suggest that AIs might be even more effective in the prevention of ER-positive breast cancer. However, these agents only prevent ER-positive breast cancer. Therefore, current research is focused on identifying preventive therapies for other forms of breast cancer such as human epidermal growth factor receptor 2 (HER2)-positive and triple-negative breast cancer (TNBC, breast cancer that does express ER, progesterone receptor, or HER2). HER2-positive breast cancers are currently treated with anti-HER2 therapies including trastuzumab and lapatinib, and preclinical and clinical studies are now being conducted to test these drugs for the prevention of HER2-positive breast cancers. Several promising agents currently being tested in cancer prevention trials for the prevention of TNBC include poly(ADP-ribose) polymerase inhibitors, vitamin D, and rexinoids, both of which activate nuclear hormone receptors (the vitamin D and retinoid X receptors). This review discusses currently used breast cancer preventive drugs, and describes the progress of research striving to identify and develop more effective preventive agents for all forms of breast cancer.

The Patient's Anastrozole Compliance to Therapy (PACT) Program: a randomized, in-practice study on the impact of a standardized information program on persistence and compliance to adjuvant endocrine therapy in postmenopausal women with early breast cancer

BACKGROUND

Compliance and persistence are often overlooked in adjuvant breast cancer treatment.

PATIENTS AND METHODS

PACT was a prospective, multicenter, randomized, open, parallel-group study assessing whether educational materials (EMs) enhanced compliance with aromatase inhibitor (AI) therapy in postmenopausal women with early, hormone-receptor-positive (HR+) breast cancer. The primary end points were compliance (proportion taking ≥ 80% anastrozole) at 12 months and persistence (proportion reporting anastrozole intake during the study period).

RESULTS

Four thousand eight hundred and forty-four patients were randomly assigned 1:1 to receive standard therapy or standard therapy with EMs. There was no difference between arms in compliance (N = 2740; 88.5%/88.8%, respectively, P = 0.81) or persistence rates (N = 2740; 40.5%/43.0%, respectively, P = 0.18). Modified end point analyses found no differences in compliance between arms based on the classification of: (i) patients with missing documentation or follow-up visit <9 months as non-compliant (N = 4397, P = 0.15); (ii) patients with early (≤ 292 days) 12-month follow-up documentation excluded (N = 4091, P = 0.19); (iii) patients reaching ≥ 80% compliance during individual follow-up as compliant (N = 4397, P = 0.26). Modified persistence analyses found no difference between arms (N = 4397, P = 0.37).

CONCLUSIONS

Addition of EMs to standard therapy did not significantly affect compliance and persistence with adjuvant anastrozole. CLINICALTRIALS ID: NCT00555867.

Persistence in patients with breast cancer treated with tamoxifen or aromatase inhibitors: a retrospective database analysis

Compliance and persistence are often underestimated in breast cancer (BC) treatment. The aim of our study was to analyze the persistence with tamoxifen (TAM) and aromatase inhibitors (AI) in postmenopausal women with hormone-receptor-positive BC and to identify determinants of non-persistence. We used data of the Disease Analyzer database (IMS HEALTH, Germany) including 2,067 general practices and 397 gynecological practices. Out of a dataset of 15 million patients, we identified BC patients with a first-time TAM or AI prescriptions from October 2001 to December 2010. For persistence analyses, 12,412 women on tamoxifen, 2,796 on anastrozole, 647 on exemestane, and 1,657 on letrozole met the inclusion/exclusion criteria. Within 3 years of follow-up, the discontinuation rates increased to 52.2 % for tamoxifen, 47 % for anastrozole, 55.1 % for exemestane, and 44.3 % for letrozole treated women. A minor proportion of patients switched to a different endocrine treatment; 33 % tamoxifen, 20 % anastrozole, 22.9 % exemestane, and 23 % letrozole. The multivariate hazard ratios of the cox regression models showed that patients younger than 50 were most likely to discontinue initial therapy when compared with the reference group of women over 70 (p < 0.001). In contrast, patients treated in gynecologist practice had significantly longer persistence than patients who obtained their prescriptions in general practitioner practice (p < 0.001). In addition, the presence of the co morbidities like diabetes (p < 0.001) or depression (p < 0.002) was also associated with decreased risk of treatment discontinuation. Persistence with all endocrine treatments in women with hormone-receptor-positive BC is low and needs to be significantly increased to improved outcome in clinical practice. Further research is required to understand this complex issue.

Aromatase inhibitor-associated bone loss and its management with bisphosphonates in patients with breast cancer

Postmenopausal women have an increased risk of osteopenia and osteoporosis due to loss of the bone-protective effects of estrogen. Disease-related processes may also contribute to the risk of bone loss in postmenopausal women with breast cancer. One of the most common and severe safety issues associated with cancer therapy for patients with breast cancer is bone loss and the associated increase in risk of fractures. This paper reviews the recent literature pertaining to aromatase inhibitor (AI)-associated bone loss, and discusses suggested management and preventative approaches that may help patients remain on therapy to derive maximum clinical benefit. A case study is presented to illustrate the discussion. We observed that AIs are in widespread use for women with hormone receptor-positive breast cancer and are now recommended as adjuvant therapy, either as primary therapy or sequential to tamoxifen, for postmenopausal women. AIs target the estrogen biosynthetic pathway and deprive tumor cells of the growth-promoting effects of estrogen, and AI therapies provide benefits to patients in terms of improved disease-free survival. However, there is a concern regarding the increased risk of bone loss with prolonged AI therapy, which can be managed in many cases with the use of bisphosphonates and other interventions (eg, calcium, vitamin D supplementation, exercise).

Effects of exemestane and tamoxifen on hormone levels within the Tamoxifen Exemestane Adjuvant Multicentre (TEAM) trial: results of a German substudy

AIM

The aim of this study was to compare the effects of exemestane and tamoxifen on hormone levels in postmenopausal patients with hormone receptor-positive breast cancer within a Germany substudy of the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial.

METHODS

Within the TEAM trial, patients were randomized to receive adjuvant treatment with exemestane for 5 years or tamoxifen for 2.5-3 years followed by exemestane for 2-2.5 years. Serum levels of testosterone, dehydroepiandrosterone sulfate (DHEAS), sex hormone binding globulin (SHBG), follicle stimulating hormone (FSH) and parathyroid hormone (PTH)-intact were measured at screening and after 3, 6 and 12 months of treatment.

RESULTS

Data on hormone levels were available from 63 patients in the tamoxifen arm and 68 patients in the exemestane arm. Treatment with exemestane resulted in decreases from baseline in SHBG and PTH-intact levels, and increases from baseline in testosterone, DHEAS and FSH levels. Tamoxifen treatment resulted in increases from baseline in SHBG and PTH-intact, whereas levels of testosterone and FSH decreased and DHEAS levels did not change. At all time points assessed, the absolute change from baseline was significantly different between tamoxifen and exemestane for testosterone, SHBG, FSH and PTH-intact (all p < 0.0001).

CONCLUSIONS

Exemestane and tamoxifen had statistically significantly different effects on hormone levels, including testosterone, SHBG, FSH and PTH-intact.

Patient and physician perceptions on continuing aromatase inhibitors beyond the 5-year mark

Aromatase inhibitors (AIs) have been shown to improve disease-free survival and in certain cases, overall survival in the treatment of postmenopausal women with hormone receptor positive early breast cancer. Trials are ongoing to determine if AI therapy should be continued for patients who have already completed 5 years of AI treatment. The objective of this study was to assess the minimum disease-free and overall survival benefit acceptable to physicians and to women undergoing AI therapy to continue treatment beyond 5 years. A self-administered survey was completed by women with stage I-III breast cancer, who were undergoing adjuvant AI therapy for at least 1 year. The survey assessed relevant cancer-related, treatment, social and comorbid factors, and FACT-ES (V4). Minimum acceptable treatment benefit was denoted as a percentage decrease in cancer recurrence risk, and percentage increase in survival at 5 years. Medical oncologists (MOs) treating breast cancer across Canada were also surveyed. A total of 153 patients were surveyed; median age was 60, 51% had node-negative disease, 89% had prior radiation therapy, 61% had prior chemotherapy, and 59% had prior tamoxifen therapy. Mean duration of AI therapy was 31 months. Approximately 30% of women required a 5-year survival benefit of less than 1%, and 27.5% needed a decrease in risk of recurrence of less than 1% to continue an AI beyond the initial 5 years. In contrast, 45% of the 40 surveyed MOs required a 5-year survival benefit of at least 1-2%, and 37.5% preferred a decrease in recurrence risk of 2-5% to prescribe an AI for an additional 5 years. There was a significant correlation between severity of endocrine symptoms experienced on AIs and an increased minimum survival benefit required for women to continue therapy (r = 0.18, p = 0.036). Patients were willing to continue on AIs for smaller treatment benefits than physicians would prefer to prescribe them beyond 5 years. Patient preference to continue on AIs correlated somewhat to the severity of AI-related side effects.

Early breast cancer in the older woman

BACKGROUND

Women aged ≥65 are generally underrepresented in early breast cancer studies. Therefore, the optimal management of this group of women remains less certain.

METHODS

A literature review of recently published trials, reviews, and practice guidelines outlining the surgical and adjuvant management of early breast cancer in older women was performed.

RESULTS

Surgery remains as the cornerstone treatment for early breast cancer in the elderly. Adjuvant radiation is generally considered if the projected lifespan is >5 years. Hormone receptor-positive disease is best treated with adjuvant endocrine treatment; aromatase inhibitors and tamoxifen are both options. Evidence for the use of adjuvant chemotherapy and trastuzumab for high-risk disease in the elderly is more limited. Polychemotherapy is still preferred in fit older women. Certain toxicities from systemic treatments can be more pronounced and should be carefully managed. Treatment with systemic agents should be individualized, with consideration of patient preference, performance status, comorbidities, and projected lifespan. Molecular tumor signatures may help better select patients for treatment in the future.

CONCLUSIONS

Age in itself should not be an absolute contraindication to any breast cancer therapy. Comprehensive, multidisciplinary assessment of elderly patients is imperative in evaluating eligibility for beneficial therapies.

Chemoprevention of hormone receptor-negative breast cancer: new approaches needed

Results from clinical trials have demonstrated that it is possible to prevent estrogen-responsive breast cancers by targeting the estrogen receptor with selective estrogen receptor modulators (SERMs) (tamoxifen, raloxifene, or lasofoxifene) or with aromatase inhibitors (AIs) (anastrozole, letrozole, or exemestene). Results from breast cancer treatment trials suggest that aromatase inhibitors may be even more effective in preventing breast cancer than SERMs. However, while SERMs and aromatase inhibitors do prevent the development of many ER-positive breast cancers, these drugs do not prevent ER-negative breast cancer. These results show that new approaches are needed for the prevention of this aggressive form of breast cancer. Our laboratory and clinical efforts have been focused on identifying critical molecular pathways in breast cells that can be targeted for the prevention of ER-negative breast cancer. Our preclinical studies have demonstrated that other nuclear receptors, such as RXR receptors, vitamin D receptors, as well as others are critical for the growth of ER-negative breast cells and for the transformation of these cells into ER-negative cancers. Other studies show that growth factor pathways including those activated by EGFR, Her2, and IGFR, which are activated in many ER-negative breast cancers, can be targeted for the prevention of ER-negative breast cancer in mice. Clinical studies have also shown that PARP inhibitors are effective for the treatment of breast cancers arising in BRCA-1 or -2 mutation carriers, suggesting that targeting PARP may also be useful for the prevention of breast cancers arising in these high-risk individuals. Most recently, we have demonstrated that ER-negative breast cancers can be subdivided into four distinct groups based on the kinases that they express. These groups include ER-negative/Her-2-positive groups (the MAPK and immunomodulatory groups) and ER-negative/Her2-negative groups (the S6K and the cell cycle checkpoint groups). These groups of ER-negative breast cancers can be targeted with kinase inhibitors specific for each subgroup. These preclinical studies have supported the development of several clinical trials testing targeted agents for the prevention of breast cancer. The results of a completed Phase II cancer prevention trial using the RXR ligand bexarotene in women at high risk of breast cancer will be reviewed, and the current status of an ongoing Phase II trial using the EGFR and Her2 kinase inhibitor lapatinib for the treatment of women with DCIS breast cancer will be presented. It is anticipated that in the future these molecularly targeted drugs will be combined with hormonal agents such as SERMs or aromatase inhibitors to prevent all forms of breast cancer.

Phase I/II study of sorafenib with anastrozole in patients with hormone receptor positive aromatase inhibitor resistant metastatic breast cancer

We evaluated the use of sorafenib to overcome resistance to aromatase inhibitors (AIs) in patients with metastatic breast cancer who had disease recurrence or progression while on AIs. We performed a multi-institution phase I/II study of sorafenib and anastrozole 1 mg daily in 35 postmenopausal females with hormone receptor positive metastatic breast cancer resistant to AIs. Primary objectives were to determine the dose of sorafenib in conjunction with anastrozole and the clinical benefit rate (CBR) (complete response [CR], partial response [PR], or stable disease [SD] ≥ 24 weeks). Secondary objectives were to determine toxicity and to evaluate if response was associated with change in number of circulating endothelial cells or circulating endothelial progenitor cells. Based on the phase I portion, sorafenib 400 mg twice daily was selected as the phase II dose. Among 35 patients, 7 had SD ≥ 24 weeks, 1 had PR ≥ 24 weeks, and 14 had progressive disease (PD) ≤ 24 weeks, corresponding to a CBR of 23%. The most common adverse events (all; Grade 3/4) were fatigue (66%; 17%), diarrhea (63%; 6%), nausea (60%; 9%), and hand-foot syndrome (57%; 34%). Dose reduction occurred in 77% of the patients and 31% came off study due to toxicity. The combination of sorafenib and anastrozole demonstrated a 23% CBR in patients with hormone receptor positive, AI-resistant metastatic breast cancer, which may be attributable to the restoration of sensitivity to AIs. Toxicities occurred frequently resulting in a high rate of discontinuation.

Guidelines for Osteoprotection in Breast Cancer Patients on an Aromatase Inhibitor

Postmenopausal women are at an increased risk of osteopenia and osteoporosis due to the physiologic loss of the bone protective effects of estrogen. Additionally, disease-related risk factors also contribute to the increased fracture risk. To further complicate matters, one of the most common and severe safety issues associated with cancer therapies for breast cancer patients is bone loss and the associated increased risk of fractures. These facts underscore the need to carefully monitor bone mineral density in patients with endocrine-responsive breast cancer, and to consider adjuvant therapy that may help manage and/or prevent bone loss and fracture. Aromatase inhibitors (AIs) are now in widespread clinical use for women with hormone receptor-positive breast cancer and have replaced tamoxifen as the gold standard of care. AIs target the estrogen biosynthetic pathway and deprive tumor cells of the growth-promoting effects of estrogen. These treatments provide significant benefit to patients in terms of improved disease-free and overall survival. Adversely, there is a concern of an increased risk of bone loss with prolonged therapy consequently leading to an increased fracture risk. This manuscript will review the recent literature pertaining to AI-associated bone loss and discuss suggested management and preventative approaches that may help patients remain on therapy to derive the most clinical benefits.