Breast cancer

What is breast cancer?

Breast cancer occurs when abnormal cells form in the tissues of the breast, usually creating a mass, or tumour. Around one in eight women will be diagnosed with breast cancer during her lifetime, and it is the second most common cause of cancer death in women.

In the United States, the American Cancer Society estimated for 2020 about 276,480 new cases of invasive breast cancer in women, along with about 48,530 new cases of carcinoma in situ (CIS) — a non-invasive condition that is the earliest form of breast cancer. It also estimated that about 42,170 women would die from the disease. Although it is rare, men can develop breast cancer too: an estimated 2,620 men were expected to be diagnosed in the United States in 2020.

Types of breast cancer

The more common types of breast cancer include:

• Ductal carcinoma in situ (DCIS): starts in the milk ducts and has not spread to nearby breast tissue. It is non-invasive, but can become invasive if left untreated.
• Invasive (or infiltrating) ductal carcinoma (IDC): the most common type, which starts in the milk ducts and spreads to nearby breast tissue.
• Invasive lobular carcinoma (ILC): an invasive cancer that starts in the breast lobules, or milk glands.
• Triple-negative breast cancer (TNBC): an invasive cancer that tests negative for human epidermal growth factor receptor 2 (HER2), oestrogen receptors (ER) and progesterone receptors (PR).
• Inflammatory breast cancer (IBC): a more aggressive, fast-growing invasive cancer that spreads to the skin and lymph vessels of the breast.
• Metastatic breast cancer (MBC): invasive breast cancer that has spread to other parts of the body, most commonly the lungs, liver, bones or brain.

Risk factors

Some risk factors for breast cancer relate to genetics and personal history, while others relate to lifestyle and environment.

Genetic and personal factors include:

• Gender: women are 100 times more likely to develop breast cancer than men.
• Age: the risk increases with age.
• Race: Caucasian women are more likely to develop breast cancer than women of other races.
• Family history: a family history of breast or ovarian cancer raises the risk.
• Personal history: women previously diagnosed with breast cancer are more likely to develop it again, as are those with non-cancerous breast conditions such as atypical hyperplasia or lobular carcinoma in situ.
• Reproductive history: starting periods early (before age 12) or reaching menopause late (after age 55) increases the risk, owing to longer exposure to hormones.
• Genetic mutations: inherited changes in certain genes, such as BRCA1 and BRCA2, increase the risk.
• Dense breasts: women with dense breasts are more likely to develop breast cancer.

Lifestyle and environmental factors include:

• Lack of physical activity: a sedentary lifestyle raises the risk.
• Being overweight or obese: postmenopausal women who are overweight or obese are at higher risk.
• Alcohol: women who drink alcohol frequently have a higher risk.
• Radiation to the chest: radiotherapy to the chest or breasts before the age of 30 can increase the risk.
• Hormone therapy: taking combined hormone replacement therapy, as prescribed for menopause, for more than five years can increase the risk.

Signs and symptoms

Signs and symptoms of breast cancer may include:

• a new lump, thickening or swelling in the breast
• a change in the size, shape or appearance of the breast
• changes to the skin over the breast or nipple, such as redness, pitting, peeling, scaling, crusting or flaking
• breast pain
• retraction of the nipple, or pain in the nipple area
• nipple discharge other than breast milk, such as blood
• swollen lymph nodes

How it's detected and diagnosed

Breast cancer may be found and diagnosed using a combination of tests:

• screening tests
• breast ultrasound
• breast MRI
• breast biopsy
• other imaging tests, such as CT, PET and bone scans, which can show whether breast cancer has spread to other parts of the body

Treatment options

After diagnosis, your doctor will establish the stage of the disease and then discuss the options best suited to your overall health, medical history and staging results. Regular follow-up appointments and periodic monitoring are strongly recommended. Treatment may include:

• Surgery: a local treatment to remove the tumour. The two main types are:
• breast-conserving surgery — also known as a lumpectomy, quadrantectomy, partial mastectomy or segmental mastectomy — which removes only the part of the breast containing the tumour, along with some surrounding tissue
• mastectomy — removing the entire breast and, occasionally, nearby tissue
• Radiotherapy: high-powered energy beams used to kill cancer cells, either alone or with chemotherapy. The two main types used for breast cancer are external beam radiation therapy (EBRT) and brachytherapy.
• Chemotherapy: drugs that kill cancer cells throughout the body, given intravenously or orally. They may be given before surgery (neoadjuvant) or after it (adjuvant).
• Targeted therapy: drugs that act on specific abnormalities within cancer cells.
• Hormonal therapy: drugs that lower hormones such as oestrogen and progesterone, or prevent them from attaching to receptors on breast cancer cells.
• Immunotherapy: immune cells, or drugs that prompt the immune system, used to kill cancer cells.
• Alternative treatments: other evidence-based approaches used to attack cancer cells.

Reducing your risk

You can lower your risk of breast cancer by:

• attending breast cancer screening
• carrying out regular breast self-examination
• limiting alcohol
• eating a healthy diet
• exercising regularly
• maintaining a healthy weight
• limiting postmenopausal hormone therapy