Breast Cancer Polygenic-Risk Score Influence on Risk-Reducing Endocrine Therapy Use: Genetic Risk Estimate (GENRE) Trial 1-Year and 2-Year Follow-Up

Refinement of breast cancer risk estimates with a polygenic-risk score (PRS) may improve uptake of risk-reducing endocrine therapy (ET). A previous clinical trial assessed the influence of adding a PRS to traditional risk estimates on ET use. We stratified participants according to PRS-refined breast cancer risk and evaluated ET use and ET-related quality of life (QOL) at 1-year (previously reported) and 2-year follow-ups. Of 151 participants, 58 (38.4%) initiated ET, and 22 (14.6%) discontinued ET by 2 years; 42 (27.8%) and 36 (23.8%) participants were using ET at 1- and 2-year follow-ups, respectively. At the 2-year follow-up, 39% of participants with a lifetime breast cancer risk of 40.1% to 100.0%, 18% with a 20.1% to 40.0% risk, and 16% with a 0.0% to 20.0% risk were taking ET (overall P = 0.01). Moreover, 40% of participants whose breast cancer risk increased by 10% or greater with addition of the PRS to a traditional breast cancer-risk model were taking ET versus 0% whose risk decreased by 10% or greater (P = 0.004). QOL was similar for participants taking or not taking ET at 1- and 2-year follow-ups, although most who discontinued ET did so because of adverse effects. However, these QOL results may have been skewed by the long interval between QOL surveys and lack of baseline QOL data. PRS-informed breast cancer prevention counseling has a lasting, but waning, effect over time. Additional follow-up studies are needed to address the effect of PRS on ET adherence, ET-related QOL, supplemental breast cancer screening, and other risk-reducing behaviors.

PREVENTION RELEVANCE

Risk-reducing medications for breast cancer are considerably underused. Informing women at risk with precise and individualized risk assessment tools may substantially affect the incidence of breast cancer. In our study, a risk assessment tool (IBIS-polygenic-risk score) yielded promising results, with 39% of women at highest risk starting preventive medication.

Implementation of Risk-reducing Strategies for Breast Cancer is Long Overdue

Despite strong evidence that it is efficacious, chemoprevention has been underused in eligible women. Reasons offered not to adopt and initiate strategies to reduce the risk of breast cancer include the fear of adverse effects, medication costs, lack of reasonably accurate and feasible methods for assessing an individual's personal risk, and lack of established risk thresholds that maximize benefit and minimize harms. The article by Macdonald and colleagues remind us that the problem of lack of uptake of risk-reducing medications for breast cancer remains a worldwide clinical challenge despite endorsements from national and international organizations that recommend the use of risk-reducing medications for breast cancer with level I evidence. Several strategies are suggested to improve uptake and utilization of safe and effective chemoprevention medications with high therapeutic indices.See related article by Macdonald et al., p. 131.

Breast cancer risk reduction: Notable achievements and remaining challenges

Millions of women in the United States are at increased risk of breast cancer. Multiple prospective, randomized clinical trials have demonstrated both the efficacy and safety of selective estrogen receptor modulators and aromatase inhibitors in reducing substantially the risk of invasive breast cancer in women at increased risk. Published tables are available to aid clinicians in shared decision-making regarding drug interventions with their patients who are at increased risk of breast cancer. Both professional and governmental agencies have advised that these interventions should be offered to women at increased risk of breast cancer. Doing so would reduce breast cancer morbidity substantially.

Role of hormones in cancer prevention

Risk for breast cancer can be easily and rapidly assessed using validated, quantitative models. Multiple randomized studies show that the selective estrogen response modifiers (SERMs) tamoxifen and raloxifene can safely reduce the risk of invasive breast cancer in both pre- and postmenopausal women. Treatment resulted in a 38% reduction in breast cancer incidence, and 42 women would need to be treated to prevent one breast cancer event in the first 10 years of follow-up. Reduction was larger in the first 5 years of follow-up than in years 5 to 10, but no studies treated patients for longer than 5 years. Thromboembolic events were significantly increased with all SERMs, whereas vertebral fractures were reduced. Tamoxifen provides net benefit to all premenopausal women who are at increased risk, whereas raloxifene reduces risk nearly as much in postmenopausal women and offers increased safety. Both tamoxifen and raloxifene reduce the incidence of in situ cancers. Lasofoxifene reduced the risk of breast cancer by 79% in postmenopausal women with osteoporosis. The MAP3 trial showed a 65% reduction in the annual incidence of invasive breast cancer in postmenopausal women who were at moderately increased risk for breast cancer who took the aromatase inhibitor exemestane. The IBIS-II trial showed a 53% reduction in the risk of invasive breast cancer in postmenopausal women aged 40 to 70 who took the aromatase inhibitor anastrozole. Of the 50 million white women in the United States aged 35 to 79, 2.4 million would have a positive benefit/risk index for chemoprevention.

Ongoing data from the breast cancer prevention trials: opportunity for breast cancer risk reduction

Selective estrogen receptor modulators (SERMs) reduce the risk of recurrence of invasive breast cancer and the incidence of first breast cancers in women who are at increased risk. Multiple, randomized clinical trials have shown both the efficacy and safety of SERMs in reducing the risk of breast cancer. Long-term follow-up as long as 20 years in the randomized trials shows persistent efficacy with acceptable safety. Hormone replacement therapy given concurrently with tamoxifen abrogates its preventive effect, but women with atypical hyperplasia derive particular benefit from SERM therapy. Aromatase inhibitors also reduce the risk of developing invasive breast cancer, but the experience with them for risk reduction is limited to few trials. National organizations have made recommendations to use SERMs and aromatase inhibitors to reduce the risk of breast cancer in high-risk women and additional efforts should be made to increase their use in clinical practice, where the number of women needed to treat to prevent one case of breast cancer conforms to accepted standards of preventive medicine.

Women's preferences for selective estrogen reuptake modulators: an investigation using protection motivation theory

OBJECTIVE

Selective estrogen receptor modulators (SERMs) reduce breast cancer risk by 38%. However, uptake is low and the reasons are not well understood. This study applied protection motivation theory (PMT) to determine factors associated with intention to take SERMs.

METHODS

Women at increased risk of breast cancer (N=107), recruited from two familial cancer clinics in Australia, completed a questionnaire containing measures of PMT constructs. Hierarchical multiple linear regression analysis was used to analyze the data.

RESULTS

Forty-five percent of women said they would be likely or very likely to take SERMs in the future. PMT components accounted for 40% of variance in intention to take SERMs. Perceived vulnerability, severity and response efficacy appeared the most influential in women's decisions to take or not take SERMs.

CONCLUSION

Many women are interested in SERMs as a risk management option. Accurate risk estimation and an understanding of the benefits of SERMs are critical to women's decision making.

PRACTICE IMPLICATIONS

Health professionals need to explore women's perceptions of their risk and its consequences, as well as providing clear evidence-based information about the efficacy of SERMs. Exploring the source and strength of beliefs about SERMs may allow more effective, tailored counseling.

Women's preferences for selective estrogen reuptake modulators: an investigation using the time trade-off technique

Purpose

Selective Estrogen Receptor Modulators (SERMs) reduce the risk of breast cancer for women at increased risk by 38%. However, uptake is extremely low and the reasons for this are not completely understood. The aims of this study were to utilize time trade-off methods to determine the degree of risk reduction required to make taking SERMs worthwhile to women, and the factors associated with requiring greater risk reduction to take SERMs.

Methods

Women at increased risk of breast cancer (N = 107) were recruited from two familial cancer clinics in Australia. Participants completed a questionnaire either online or in pen and paper format. Hierarchical multiple linear regression analysis was used to analyze the data.

Results

Overall, there was considerable heterogeneity in the degree of risk reduction required to make taking SERMs worthwhile. Women with higher perceived breast cancer risk and those with stronger intentions to undergo (or who had undergone) an oophorectomy required a smaller degree of risk reduction to consider taking SERMs worthwhile.

Conclusion

Women at increased familial risk appear motivated to consider SERMs for prevention. A tailored approach to communicating about medical prevention is essential. Health professionals could usefully highlight the absolute (rather than relative) probability of side effects and take into account an individual’s perceived (rather than objective) risk of breast cancer.

Exemestane for primary prevention of breast cancer in postmenopausal women

PURPOSE

The benefits and risks of exemestane for the primary prevention of breast cancer are discussed and compared with other breast cancer chemoprevention therapies.

SUMMARY

Selective estrogen-receptor modulators (SERMs) are the current mainstay for primary prevention of breast cancer. As an alternative, exemestane, an aromatase inhibitor, has been evaluated for breast cancer prevention in postmenopausal women. A study of 4560 high-risk postmenopausal women taking exemestane 25 mg daily for a median of three years found a 65% relative reduction in the annual occurrence of invasive breast cancer compared with placebo (0.19% versus 0.55%; hazard ratio, 0.35; 95% confidence interval [CI], 0.18-0.70; p = 0.002) and a 53% reduction in invasive plus noninvasive breast cancer (0.35% versus 0.77%; hazard ratio, 0.47; 95% CI, 0.27-0.79; p = 0.04). Adverse effects from exemestane are generally mild, with the most common being diarrhea, joint pain, and menopausal-related symptoms. Importantly, exemestane did not increase the risks of endometrial cancers, thromboembolism, cardiovascular events, or cataracts. However, joint stiffness and arthralgia were more common when compared with tamoxifen or raloxifene. Ongoing clinical trials with other aromatase inhibitors are underway to evaluate the benefits and long-term skeletal risks.

CONCLUSION

Exemestane 25 mg daily taken for at least three years is a new option for the prevention of breast cancer in high-risk postmenopausal women. Indirectly compared with SERMs, exemestane has a similar frequency of bothersome adverse effects without the risk of thromboembolic events or endometrial cancer, though an increased risk of osteoporosis is of concern.

Back to the future: mechanism-based, mutation-specific combination chemoprevention with a synthetic lethality approach

There is an increasing recognition that the mutations accompanying carcinogenesis may provide a window of therapeutic advantage designated synthetic lethality, an example of which is reported in this issue of the journal by Huang and colleagues (beginning on page 666). First discovered and studied in yeast, synthetic lethality has basic principles that have encouraged its development for treatment and now prevention in animal models of human cancer, especially malignancies refractory to standard approaches. The pros and cons of this approach and challenges in implementing it clinically are discussed.

Selective estrogen modulators for the primary prevention of breast cancer

Selective estrogen modulators can be used in the primary prevention of breast cancer in postmenopausal women.