Introduction

Breast cancer is the most common cancer diagnosed among people assigned female at birth (AFAB) in the majority of countries and therefore represents a significant global health challenge. Worldwide, an estimated 2.3 million women were diagnosed with breast cancer in 2022, leading to 670,000 deaths. The number of new cases of breast cancer is on the rise in the developing world due to increased life expectancy, growing urbanisation and the adoption of Western lifestyles.¹ 

Key risk factors for breast cancer include being assigned female at birth (AFAB) and having a family history of breast cancer. Although these are factors that we cannot influence (i.e. they are non-modifiable), there are several risk factors – including diet and nutrition, physical activity and alcohol consumption – that we can influence through lifestyle modifications. This article will discuss the role that various risk factors play in the development of breast cancer and help you understand the factors that you can change in your lifestyle so to reduce your risk of developing breast cancer. 

What is breast cancer?

Breast cancer is a disease that occurs when abnormal breast cells multiply uncontrollably, forming tumours. These tumours can spread (metastasize) to other organs of the body via the bloodstream and lymphatic system, potentially becoming fatal. Breast cancer typically starts in the cells of the milk ducts or milk-producing tissues of the breast. The earliest form, in situ, is not life-threatening and can be detected early. However, cancer cells can invade nearby breast tissue, forming tumours that cause lumps or thickening.²

Being assigned female at birth (AFAB) is the strongest risk factor for developing breast cancer. According to the World Health Organization, about 99% of breast cancers occur in people AFAB and only 0.5-1.0% occur in people assigned male at birth (AMAB).

Overview of key prevention strategies

Lifestyle modification

Diet and nutrition

An emerging epidemic of obesity-related cancers, including breast cancer, is being observed in both developed and developing regions. Obesity is a high-risk factor for premenopausal subtypes of breast cancer called oestrogen receptor-negative breast cancer and triple-negative breast cancer (TNBC). Two meta-analyses (a statistical analysis that combines the results of multiple studies) of patients with TNBC found an 80% and 43% higher risk, respectively, of developing TNBC in obese premenopausal people AFAB.³ Maintaining a healthy body weight, will lower the risk of developing breast cancer, especially among people who are middle-aged and older.

A diet rich in fruits and vegetables – particularly non-starchy vegetables (e.g. broccoli, tomatoes and courgette) and foods high in carotenoids (e.g. carrots, dark leafy greens and red bell peppers) – can help lower the risk of breast cancer. Adequate dietary calcium from dairy or non-dairy sources, such as soy, and limiting consumption of processed meats (e.g. bacon) and red meat can also reduce breast cancer risk. The Mediterranean diet is an example of a healthy eating pattern that can help reduce breast cancer risk.⁴

Physical activity

Physical activity can help maintain a healthy weight, which in turn helps to prevent breast cancer. We should all aim to reduce our sedentary time and be more active. According to the UK’s NHS, adults should target at least 150 minutes of moderate aerobic exercise per week or at least 75 minutes of vigorous aerobic exercise weekly. Aerobic exercise increases your heart rate and can include activities like walking, cycling, running and swimming. Additionally, aim to incorporate strength training exercises at least twice a week.

Alcohol consumption

Reducing alcohol consumption could significantly impact the burden of breast cancer. At a global level, alcohol consumption is responsible for an estimated 144,000 new cases of breast cancer each year and 38,000 breast cancer deaths annually, which is 8.6% of all incidence (i.e. the number of new cases per year) and 7.3% of mortality.⁵ 

The impact of alcohol consumption on breast cancer risk has been found to vary by region. For instance, in Australia, regular alcohol consumption is estimated to account for 12.6% of premenopausal breast cancer cases and 6.6% of postmenopausal breast cancer cases.⁶ In the United Kingdom, alcohol consumption is responsible for 12% of breast cancer cases.

Regular consumption of each additional drink per day results in 11 extra breast cancer cases per 1,000 women over their lifetime, up to the age of 75.⁷ The increased cancer risk from drinking one bottle of wine per week is roughly equivalent to smoking ten cigarettes per week, with breast cancer contributing to most of that risk.⁸

UK government guidance for people who drink alcohol regularly is to:

• Limit alcohol intake to no more than 14 units per week – the equivalent of six pints of beer or 10 small glasses of lower-strength wine
• Spread drinking over at least three days if they consume up to 14 units per week

Smoking cessation

Smoking has higher all-cause mortality rates, including deaths related to breast cancer. Additionally, it negatively impacts long-term survival following successful breast cancer treatment. Research indicates that smoking cessation among patients diagnosed with breast cancer can lead to prolonged survival when started as early as the time of diagnosis.⁹

Regular screening and early detection

Cancer screening is the process of testing healthy individuals for early signs of cancer. Breast screening employs an imaging technique called mammography, which involves capturing X-ray images of the breasts. Screening aids detection of breast cancer at an early stage when it is too small to be identified by touch or sight. These early-stage cancers are typically easier to treat than those diagnosed later. The NHS Breast Screening Programme invites all people AFAB registered with a GP aged 50 to 70 for screening every three years.

People AFAB of all ages should conduct breast self-exams at least once per month. Those who menstruate should perform breast self-exams a few days after the end of their period. Postmenopausal individuals should schedule their breast self-exams for the same day each month (e.g., the 1st or 15th day).

Breast cancers detected at the localised stage (stage I and certain stage II tumours) have an overall 5-year relative survival rate of 99%. In contrast, breast cancers identified at the regional stage (stage II or III) yield a 5-year relative survival rate of 85%. However, diagnosing breast cancer at the advanced stage (some stage III and all stage IV) results in an overall 5-year relative survival rate of 27%.¹⁰

Genetic considerations

Some people face an elevated risk of developing breast cancer due to their family history. For instance, having a first-degree relative (parent, sibling, or child) diagnosed with breast cancer roughly doubles the risk. This risk escalates further if additional close relatives have had breast cancer or had cancer before the age of 50. Moreover, specific genetic mutations can heighten breast cancer susceptibility, with BRCA1 and BRCA2 being notable examples.

While these genes typically act as safeguards against cancer, inheriting a pathogenic variant (mutation) in either increases the risk of developing breast cancer.¹¹ Individuals carrying a BRCA1 or BRCA2 mutation (or both) may face a risk of up to 72% of being diagnosed with breast cancer during their lifetime. Cases of breast cancer associated with a BRCA1 or BRCA2 mutation tend to develop in younger patients. 

Hormonal factors

Postmenopausal women or those who have undergone surgery to remove their ovaries (known as oophorectomy) may be prescribed oestrogen, progestin, or both in tablet form to replace the oestrogen no longer produced by the ovaries. This treatment is known as hormone replacement therapy (HRT). However, initiating oestrogen therapy close to the time of menopause has been linked to a heightened risk of breast cancer.¹²

Exposure to toxins

Our hormones can be disrupted by certain substances known as endocrine-disrupting chemicals (EDCs). They can mimic our natural hormones, particularly oestrogen, which accelerates cell division. An increased rate of cell division raises the likelihood of mutations associated with breast cancer. These chemicals are prevalent in everyday items such as cosmetics, cleaning products, and food. Hence, it is important to be vigilant about the products we use at home and to scrutinise the ingredients list before use to make healthy choices.¹³

It is advisable to opt for stainless steel cookware when cooking. Perfluoroalkyl substances (PFAS) are chemicals found in certain non-stick cookware and food packaging, and avoiding them can help reduce exposure. When reheating food in a microwave, using glass containers instead of plastic is advisable, as some plastic containers may release harmful chemicals when heated.

Education and awareness

Through public health campaigns aimed at enhancing awareness of the signs and symptoms of breast cancer, alongside educating their families about the significance of early detection and treatment, more women could seek medical advice when they suspect breast cancer, thus intervening before cancer progresses. This initiative remains feasible even in regions where mammographic screening is currently impractical.¹⁴

Summary

Breast cancer poses a significant global health challenge, with its incidence on the rise in both developed and developing countries. 

Various factors contribute to an increase in cancer, including lifestyle factors, hormonal influences, genetic predispositions, and environmental exposures. However, preventive measures can play a crucial role in reducing the burden of breast cancer. Lifestyle modifications such as maintaining a healthy diet, engaging in regular physical activity, limiting alcohol consumption, and quitting smoking are essential to reducing breast cancer risk. Additionally, regular screening and early detection, genetic considerations, hormonal factors, and minimising exposure to toxins are vital strategies in breast cancer prevention. Education and awareness initiatives further empower individuals to seek timely medical intervention and early diagnosis. 

Overall, a multifaceted approach encompassing prevention, screening, and education is imperative in combating the escalating incidence of breast cancer worldwide.