Chapter 5: Breast Cancer

INTRODUCTION

Breast cancer is the most commonly diagnosed cancer among American women, with nearly 276,500 invasive diagnoses expected in 2020 in the United States alone.¹ Over the past three decades, treatment for breast cancer has improved dramatically, including new systemic treatments, surgical and radiation techniques, molecular profiling, and imaging modalities. Despite these advances, breast cancer remains the second-leading cause of female cancer deaths in the United States, with over 42,000 deaths estimated to occur in 2020.¹

If breast cancer morbidity and mortality rates are to improve, more must be done to increase early detection and prevention rates by identifying the women at highest risk for breast cancer. Effective breast cancer screening and prevention strategies have been developed, such as genetic testing, use of breast magnetic resonance imaging (MRI), preventive medications, and risk-reducing surgeries. However, broad implementation of these measures has been limited to date, in part due to lack of available training for providers who directly care for patients at increased risk.

As such, the aim of this chapter is to provide a practical, clinical approach to breast cancer risk assessment, genetic testing, and risk management for patients deemed to be at increased risk of breast cancer. Specific topics include breast cancer risk factors, family history risk modeling, referral criteria for genetic testing and interpretation of testing results, clinical management of high-risk patients with either a specific hereditary breast cancer syndrome or increased risk based on family history, and discussion on how these syndromes might specifically affect breast cancer treatment.

BREAST CANCER RISK ASSESSMENT

The purpose of formal breast cancer risk assessment should be to identify those women at highest risk based on personal or family history and, in particular, those who require referral for genetic counseling and testing. Identifying high-risk patients allows an opportunity for providers to counsel their patients on potential breast cancer risk reduction options, such as enhanced screening, surgical interventions, and/or risk-reducing medications. Moreover, breast cancer risk assessments can be used to counsel both genetic mutation carriers and noncarriers on how best to lower their risk of breast cancer, as well as other cancers, through appropriate screening and healthy lifestyle modifications.

Breast Cancer Risk Factors

Risk factors for breast cancer have traditionally been grouped into six major categories, namely demographic, familial/genetic, reproductive/hormonal, lifestyle, personal history, and other causes of risk. Each of these groups are discussed in detail here and are summarized in Table 5.1.