Endocrine prevention of breast cancer

Validation of a clinical breast cancer risk assessment tool combining a polygenic score for all ancestries with traditional risk factors

PURPOSE

We previously described a combined risk score (CRS) that integrates a multiple-ancestry polygenic risk score (MA-PRS) with the Tyrer-Cuzick (TC) model to assess breast cancer (BC) risk. Here, we present a longitudinal validation of CRS in a real-world cohort.

METHODS

This study included 130,058 patients referred for hereditary cancer genetic testing and negative for germline pathogenic variants in BC-associated genes. Data were obtained by linking genetic test results to medical claims (median follow-up 12.1 months). CRS calibration was evaluated by the ratio of observed to expected BCs.

RESULTS

Three hundred forty BCs were observed over 148,349 patient-years. CRS was well-calibrated and demonstrated superior calibration compared with TC in high-risk deciles. MA-PRS alone had greater discriminatory accuracy than TC, and CRS had approximately 2-fold greater discriminatory accuracy than MA-PRS or TC. Among those classified as high risk by TC, 32.6% were low risk by CRS, and of those classified as low risk by TC, 4.3% were high risk by CRS. In cases where CRS and TC classifications disagreed, CRS was more accurate in predicting incident BC.

CONCLUSION

CRS was well-calibrated and significantly improved BC risk stratification. Short-term follow-up suggests that clinical implementation of CRS should improve outcomes for patients of all ancestries through personalized risk-based screening and prevention.

Anastrozole for the prevention of breast cancer in high-risk postmenopausal women: cost-effectiveness analysis in the UK and the USA

PURPOSE

The effectiveness of anastrozole for breast cancer prevention has been demonstrated. The objective of this study was to evaluate the cost-effectiveness of anastrozole for the prevention of breast cancer in women with a high risk of breast cancer and to determine whether anastrozole for the primary prevention of breast cancer can improve the quality of life of women and save health-care resources.

METHODS

A decision-analytic model was used to assess the costs and effects of anastrozole prevention versus no prevention among women with a high risk of breast cancer. The key parameters of probability were derived from the IBIS-II trial, and the cost and health outcome data were derived from published literature. Costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs) were calculated for the two strategies,One-way and probabilistic sensitivity analyses were performed.

RESULTS

In the base case, the incremental cost per QALY of anastrozole prevention was £125,705.38/QALY in the first 5 years compared with no prevention in the UK, above the threshold of WTP (£3,000/QALY),and in the 12-year period, the ICER was £8,313.45/QALY, less than WTP. For the US third-party payer, ICER was $134,232.13/QALY in the first 5 years and $8,843.30/QALY in the 12 years, both less than the WTP threshold ($150,000/QALY).

CONCLUSION

In the UK and US, anastrozole may be a cost-effective strategy for the prevention of breast cancer in high-risk postmenopausal women. Moreover, the longer the cycle of the model, the higher the acceptability. The results of this study may provide a scientific reference for decision-making for clinicians, patients, and national medical and health care government departments.

Factors associated with adherence to medications for lowering breast cancer risk between female Medicare beneficiaries in Alabama and nationwide

PURPOSE

The U.S. Preventive Services Task Force recommends use of selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs) for breast cancer (BC) prevention. We examined factors associated with adherence to SERMs/AI treatments among female Medicare beneficiaries in Alabama and those nationwide.

METHODS

This retrospective new user cohort study analyzed the 2013-2016 Medicare administrative claims data files (100% Alabama and random 5% national samples). Female Medicare beneficiaries without invasive BC and osteoporosis, continuously enrolled in Medicare Parts A, B, and D for at least 18 months (with a 6-month washout and a 12-month follow-up period) in 2013-2016. Among beneficiaries who initiated (6-month washout) any of the SERMs/AIs (tamoxifen, raloxifene, anastrozole, and exemestane), we examined their 1-year treatment adherence using proportion of days covered (PDC) and operationalized as both continuous (0-1) and dichotomized (≥ 80% as adherent and < 80% as non-adherent) outcomes. Multivariable logistic models were used to identify factors associated with adherence (PDC ≥ 80%) among Alabama and national samples, respectively.

RESULTS

A total of 885 women in Alabama and 1,213 women in national sample initiated these SERMs/AI treatments. Among those with ≥ 2 prescriptions (n = 479 in Alabama and n = 870 in national sample), Mean PDC was 0.74 [standard deviation (SD) = 0.30] among Alabamian women, similar to those in the national sample [0.71 (SD = 0.31), p = 0.09]. Use of mammography prior to treatment initiation was associated with higher likelihood of adherence to treatments in both samples.

CONCLUSION

Our findings highlight the importance of access to preventive services such as mammography to better adherence to BC preventive treatments among female Medicare beneficiaries.

Systemic and Local Strategies for Primary Prevention of Breast Cancer

One in eight women will develop breast cancer in the US. For women with moderate (15-20%) to average (12.5%) risk of breast cancer, there are few options available for risk reduction. For high-risk (>20%) women, such as BRCA mutation carriers, primary prevention strategies are limited to evidence-based surgical removal of breasts and/or ovaries and anti-estrogen treatment. Despite their effectiveness in risk reduction, not many high-risk individuals opt for surgical or hormonal interventions due to severe side effects and potentially life-changing outcomes as key deterrents. Thus, better communication about the benefits of existing strategies and the development of new strategies with minimal side effects are needed to offer women adequate risk-reducing interventions. We extensively review and discuss innovative investigational strategies for primary prevention. Most of these investigational strategies are at the pre-clinical stage, but some are already being evaluated in clinical trials and others are expected to lead to first-in-human clinical trials within 5 years. Likely, these strategies would be initially tested in high-risk individuals but may be applicable to lower-risk women, if shown to decrease risk at a similar rate to existing strategies, but with minimal side effects.

Targeting nuclear hormone receptors for the prevention of breast cancer

Advancements in research have led to the steady decline of breast cancer mortality over the past thirty years. However, breast cancer incidence has continued to rise, resulting in an undue burden on healthcare costs and highlighting a great need for more effective breast cancer prevention strategies, including targeted chemo preventative agents. Efforts to understand the etiology of breast cancer have uncovered important roles for nuclear receptors in the development and progression of breast cancer. Targeted therapies to inhibit estrogen receptor (ER) and progesterone receptor (PR) signaling (selective ER modulators, aromatase inhibitors and selective PR modulators) have shown great promise for the treatment and prevention of hormone receptor (HR)-positive breast cancer. However, these drugs do not prevent HR-negative disease. Therefore, recent efforts have focused on novel targeted therapies with the potential to prevent both HR-positive and HR-negative breast cancer. Among these include drugs that target other nuclear receptors, such as retinoic acid receptor (RAR), retinoid X receptor (RXR) and vitamin D receptor (VDR). In this review we provide an overview of recent preclinical and clinical trials targeting members of the nuclear receptor superfamily for the prevention of breast cancer.

Quantifying the effects of risk-stratified breast cancer screening when delivered in real time as routine practice versus usual screening: the BC-Predict non-randomised controlled study (NCT04359420)

BACKGROUND

Risk stratification as a routine part of the NHS Breast Screening Programme (NHSBSP) could provide a better balance of benefits and harms. We developed BC-Predict, to offer women when invited to the NHSBSP, which collects standard risk factor information; mammographic density; and in a sub-sample, a Polygenic Risk Score (PRS).

METHODS

Risk prediction was estimated primarily from self-reported questionnaires and mammographic density using the Tyrer-Cuzick risk model. Women eligible for NHSBSP were recruited. BC-Predict produced risk feedback letters, inviting women at high risk (≥8% 10-year) or moderate risk (≥5-<8% 10-year) to have appointments to discuss prevention and additional screening.

RESULTS

Overall uptake of BC-Predict in screening attendees was 16.9% with 2472 consenting to the study; 76.8% of those received risk feedback within the 8-week timeframe. Recruitment was 63.2% with an onsite recruiter and paper questionnaire compared to <10% with BC-Predict only (P < 0.0001). Risk appointment attendance was highest for those at high risk (40.6%); 77.5% of those opted for preventive medication.

DISCUSSION

We have shown that a real-time offer of breast cancer risk information (including both mammographic density and PRS) is feasible and can be delivered in reasonable time, although uptake requires personal contact. Preventive medication uptake in women newly identified at high risk is high and could improve the cost-effectiveness of risk stratification.

TRIAL REGISTRATION

Retrospectively registered with clinicaltrials.gov (NCT04359420).

Expression and Function of StAR in Cancerous and Non-Cancerous Human and Mouse Breast Tissues: New Insights into Diagnosis and Treatment of Hormone-Sensitive Breast Cancer

Breast cancer (BC) is primarily triggered by estrogens, especially 17β-estradiol (E2), which are synthesized by the aromatase enzyme. While all steroid hormones are derived from cholesterol, the rate-limiting step in steroid biosynthesis is mediated by the steroidogenic acute regulatory (StAR) protein. Herein, we demonstrate that StAR mRNA expression was aberrantly high in human hormone-dependent BC (MCF7, MDA-MB-361, and T-47D), modest in hormone-independent triple negative BC (TNBC; MDA-MB-468, BT-549, and MDA-MB-231), and had little to none in non-cancerous mammary epithelial (HMEC, MCF10A, and MCF12F) cells. In contrast, these cell lines showed abundant expression of aromatase (CYP19A1) mRNA. Immunofluorescence displayed qualitatively similar patterns of both StAR and aromatase expression in various breast cells. Additionally, three different transgenic (Tg) mouse models of spontaneous breast tumors, i.e., MMTV-Neu, MMTV-HRAS, and MMTV-PyMT, demonstrated markedly higher expression of StAR mRNA/protein in breast tumors than in normal mammary tissue. While breast tumors in these mouse models exhibited higher expression of ERα, ERβ, and PR mRNAs, their levels were undetected in TNBC tumors. Accumulation of E2 in plasma and breast tissues, from MMTV-PyMT and non-cancerous Tg mice, correlated with StAR, but not with aromatase, signifying the importance of StAR in governing E2 biosynthesis in mammary tissue. Treatment with a variety of histone deacetylase inhibitors (HDACIs) in primary cultures of enriched breast tumor epithelial cells, from MMTV-PyMT mice, resulted in suppression of StAR and E2 levels. Importantly, inhibition of StAR, concomitant with E2 synthesis, by various HDACIs, at clinical and preclinical doses, in MCF7 cells, indicated therapeutic relevance of StAR in hormone-dependent BCs. These findings provide insights into the molecular events underlying the differential expression of StAR in human and mouse cancerous and non-cancerous breast cells/tissues, highlighting StAR could serve not only as a novel diagnostic maker but also as a therapeutic target for the most prevalent hormone-sensitive BCs.

Hormonal and Genetic Regulatory Events in Breast Cancer and Its Therapeutics: Importance of the Steroidogenic Acute Regulatory Protein

Estrogen promotes the development and survival of the majority of breast cancers (BCs). Aromatase is the rate-limiting enzyme in estrogen biosynthesis, and it is immensely expressed in both cancerous and non-cancerous breast tissues. Endocrine therapy based on estrogen blockade, by aromatase inhibitors, has been the mainstay of BC treatment in post-menopausal women; however, resistance to hormone therapy is the leading cause of cancer death. An improved understanding of the molecular underpinnings is the key to develop therapeutic strategies for countering the most prevalent hormone receptor positive BCs. Of note, cholesterol is the precursor of all steroid hormones that are synthesized in a variety of tissues and play crucial roles in diverse processes, ranging from organogenesis to homeostasis to carcinogenesis. The rate-limiting step in steroid biosynthesis is the transport of cholesterol from the outer to the inner mitochondrial membrane, a process that is primarily mediated by the steroidogenic acute regulatory (StAR) protein. Advances in genomic and proteomic technologies have revealed a dynamic link between histone deacetylases (HDACs) and StAR, aromatase, and estrogen regulation. We were the first to report that StAR is abundantly expressed, along with large amounts of 17β-estradiol (E2), in hormone-dependent, but not hormone-independent, BCs, in which StAR was also identified as a novel acetylated protein. Our in-silico analyses of The Cancer Genome Atlas (TCGA) datasets, for StAR and steroidogenic enzyme genes, revealed an inverse correlation between the amplification of the StAR gene and the poor survival of BC patients. Additionally, we reported that a number of HDAC inhibitors, by altering StAR acetylation patterns, repress E2 synthesis in hormone-sensitive BC cells. This review highlights the current understanding of molecular pathogenesis of BCs, especially for luminal subtypes, and their therapeutics, underlining that StAR could serve not only as a prognostic marker, but also as a therapeutic candidate, in the prevention and treatment of this life-threatening disease.