Breast Cancer Chemoprevention: Use and Views of Australian Women and Their Clinicians

Awareness and Candidacy for Endocrine Prevention and Risk Reducing Mastectomy in Unaffected High-Risk Women Referred for Breast Cancer Risk Assessment

INTRODUCTION

Primary prevention of breast cancer in women at elevated risk includes several strategies such as endocrine prevention and risk-reducing mastectomy (RRM). The objective of this study was to evaluate awareness of different preventive strategies across high-risk subgroups.

PATIENTS AND METHODS

Women referred for high risk evaluation between 2020 and 2023 completed an initial risk-assessment questionnaire that included questions around perceived lifetime risk and consideration of preventive strategies. One-way analysis of variance (ANOVA) and chi-squared tests were used to compare differences across different high-risk subgroups.

RESULTS

482 women with a median age of 43 years (20-79 years) met inclusion criteria; 183 (38.0%) germline pathogenic variant carriers (GPV), 90 (18.7%) with high-risk lesions (HRL) on breast biopsy, and 209 (43.4%) with strong family history (FH) without a known genetic predisposition. Most high-risk women reported that they had considered increased screening and surveillance (83.7%) and lifestyle strategies (80.6%), while fewer patients had considered RRM (39.8%) and endocrine prevention (27.0%). Prior to initial consultation, RRM was more commonly considered in GPV carriers (59.4%) relative to those with HRL (33.3%) or strong FH (26.3%, p < 0.001). Based on current guidelines, 206 (43%) patients were deemed eligible for endocrine prevention, including 80.5% with HRL and 39.0% with strong FH. Prior consideration of endocrine prevention was highest in patients with HRL and significantly lower in those with strong FH (47.2% HRL versus 31.1% GPV versus 18.7% FH, p = 0.001).

CONCLUSIONS

Endocrine prevention is the least considered preventive option for high-risk women, despite eligibility in a significant proportion of those presenting with HRL or strong FH.

Body composition changes during breast cancer preventive treatment with anastrozole: Findings from the IBIS-II trial

Background

Uptake to anastrozole for breast cancer prevention is low, partly due to women's concerns about side effects including gains in weight and specifically gains in body fat. Previous evidence does not link anastrozole with gains in weight, but there is a lack of data on any effects on body composition i.e. changes in fat and fat free mass. Here we assess association of anastrozole with body composition changes in a prospective sub-study from the second international breast intervention trial (IBIS-II).

Methods

Participants had DXA scans at baseline and for five years of anastrozole/placebo and beyond (between March 2004 and September 2017. Primary outcomes were changes in body weight, body fat and fat free mass at 9-18 months. A linear model was used to estimate the size of a differential effect in these outcomes by randomised treatment allocation adjusted for baseline value and time since last scan, age, 10-year breast cancer risk, smoking and HRT status.

Results

203 postmenopausal women were recruited (n = 95 anastrozole, n = 108 placebo), mean age 58 years (SD = 5.4), BMI 28.0 kg/m2 (SD = 5.5). There was no evidence of a strong association between anastrozole or placebo and endpoints at 9-18 months; effect size (95 %CI) for anastrozole minus placebo for body weight (per/kg) -0.11 (-1.29-1.08); body fat 0.11 (-0.75-0.96) and fat free mass -0.30 (-0.79-0.19).

Conclusions

There is unlikely to be a clinically significant change to body composition with anastrozole for breast cancer prevention.

Tamoxifen and the risk of breast cancer in women with a BRCA1 or BRCA2 mutation

PURPOSE

Chemoprevention with a selective estrogen receptor modulator (tamoxifen or raloxifene) is a non-surgical option offered to high-risk women to reduce the risk of breast cancer. The evidence for tamoxifen benefit is based on trials conducted among predominantly postmenopausal women from the general population and on studies of contralateral breast cancer in women with a pathogenic variant (mutation hereafter) in BRCA1 or BRCA2. Tamoxifen has not been assessed as a primary prevention agent in women with an inherited BRCA mutation.

METHODS

We conducted a prospective analysis of tamoxifen chemoprevention and the risk of breast cancer in women with a BRCA1 or BRCA2 mutation. Data on tamoxifen (and raloxifene) use was collected by questionnaire and updated biennially. Information on incident cancers was collected by self-report and was confirmed by medical record review. In a matched analysis, we estimated the hazard ratio (HR) and 95% confidence intervals (CI) for developing a first primary breast cancer associated with tamoxifen or raloxifene use, using Cox proportional hazards analysis.

RESULTS

There were 4578 unaffected women in the cohort, of whom 137 reported tamoxifen use (3%), 83 reported raloxifene use (2%) and 12 used both drugs (0.3%). Women who used tamoxifen or raloxifene were matched 1:3 with women who used neither drug on year of birth, country of residence, year of study entry and gene (BRCA1 or BRCA2). We generated 202 matched pairs. After a mean follow-up of 6.8 years, there were 22 incident breast cancers diagnosed among tamoxifen/raloxifene users (10.9% of users) and 71 cases diagnosed among non-users (14.3% of non-users; HR = 0.64; 95% CI 0.40-1.03; P = 0.07).

CONCLUSION

Chemoprevention may be an effective risk-reduction option for BRCA mutation carriers, but further studies with longer follow-up are necessary.

Underutilisation of breast cancer prevention medication in Australia

Increased implementation of proven prevention strategies is required to combat rising breast cancer incidence. We assessed use of risk reducing medication (RRMed) by Australian women at elevated breast cancer risk. Only 2.4% had ever used RRMed. Higher breast cancer risk was statistically significantly associated with use of RRMed (OR 1.82, 95%CI: 1.08–3.07, p = 0.02 for ≥30% lifetime risk compared with 16%–29% lifetime risk), but parity, education level and family history of breast cancer were not. Breast cancer prevention medications are underutilised. Efforts are needed to incorporate breast cancer risk assessment and risk management discussions into routine health assessments for women.

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Risk-reducing medication is infrequently used by Australian women at increased risk of breast cancer.

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Higher breast cancer risk is associated with greater uptake of risk reducing medication, but not with adherence.

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Routine breast cancer risk assessment may increase risk reducing medication use.

Breast Cancer Risk Assessment and Primary Prevention Advice in Primary Care: A Systematic Review of Provider Attitudes and Routine Behaviours

Implementing risk-stratified breast cancer screening is being considered internationally. It has been suggested that primary care will need to take a role in delivering this service, including risk assessment and provision of primary prevention advice. This systematic review aimed to assess the acceptability of these tasks to primary care providers. Five databases were searched up to July-August 2020, yielding 29 eligible studies, of which 27 were narratively synthesised. The review was pre-registered (PROSPERO: CRD42020197676). Primary care providers report frequently collecting breast cancer family history information, but rarely using quantitative tools integrating additional risk factors. Primary care providers reported high levels of discomfort and low confidence with respect to risk-reducing medications although very few reported doubts about the evidence base underpinning their use. Insufficient education/training and perceived discomfort conducting both tasks were notable barriers. Primary care providers are more likely to accept an increased role in breast cancer risk assessment than advising on risk-reducing medications. To realise the benefits of risk-based screening and prevention at a population level, primary care will need to proactively assess breast cancer risk and advise on risk-reducing medications. To facilitate this, adaptations to infrastructure such as integrated tools are necessary in addition to provision of education.