By Dr Cathy Ng, Consultant Breast Surgeon, Department of Surgery, Woodlands Health

Breast cancer is the uncontrolled growth of abnormal cells that invade healthy breast tissue and have the potential to spread beyond the breast. One in 13 women will develop breast cancer in their lifetime in Singapore. According to the 2021 Cancer Registry report, breast cancer ranks as the most common cancer among women, accounting for 29.7% of all cancer cases. It is also the leading cause of cancer-related deaths in women.

Early detection, combined with appropriate treatment, is crucial to improving survival rates. Therefore, understanding the diagnosis and treatment processes is essential for everyone. Survival rates are significantly higher when breast cancer is detected at an early stage. Hence, women are encouraged to undergo regular breast screenings. Research has shown that mammography screening can reduce mortality rates by 25-30%.

Diagnosis of Breast Cancer

Breast cancer is diagnosed through a process known as triple assessment, which combines clinical, radiological, and histological evaluations. Let’s explore the main steps involved.

Clinical Assessment

Regular self-breast examinations are recommended for all women to check for lumps or changes in breast tissue. This practice helps individuals detect changes early, prompting them to seek medical advice. Women should consult a healthcare provider if any abnormalities are noticed during self-examination. During a clinical breast examination, doctors check for lumps, abnormal skin changes, nipple discharge, or signs of lymph node involvement.

Radiological Assessment

If any abnormalities are detected during the clinical assessment, the next step is radiological evaluation, typically involving mammography and ultrasound.

• Mammography: This is an X-ray of the breast taken from two different angles. It is the most commonly used screening tool for asymptomatic women over 40 years old and helps identify cancer at early, more treatable stages, before symptoms arise. However, mammography is not routinely recommended for women under 40, as the dense breast tissue can reduce its sensitivity. The sensitivity of mammography is approximately 85%. Additional views, such as magnified or compression views, may be needed to better characterize detected abnormalities.
• Ultrasound: Ultrasound is highly effective in assessing breast lumps and the status of axillary lymph nodes. It distinguishes between solid and cystic lesions and characterizes abnormal lymph nodes. The sensitivity of ultrasound is as high as 97%, with a specificity of 97%. Ultrasound is particularly useful for palpable breast masses, offering higher sensitivity than mammography.
• Magnetic Resonance Imaging (MRI): MRI uses magnetic fields and radio waves to create detailed images of breast tissue and is especially valuable in detecting cancer in dense breasts. Although it is not routinely used for all patients with suspected breast cancer, MRI may be employed for high-risk patients or for further evaluation after a mammography. It has high sensitivity but also a higher false-negative rate.

Histological Assessment

A biopsy, which involves taking a tissue sample from the breast for microscopic examination, is typically performed to confirm the diagnosis of breast cancer. This test provides information about the cancer’s characteristics and type, which is crucial for planning treatment.

Treatment of Breast Cancer

Breast cancer treatment requires a multidisciplinary approach and emphasizes personalized care. The choice of treatment depends on factors such as the cancer's stage, molecular subtype, pre-existing health conditions, and the patient’s preferences. Treatment options are generally categorized into locoregional treatments (surgery and radiotherapy) and systemic treatments (chemotherapy, hormone therapy, targeted therapy, and immunotherapy).

Surgery

Surgery is the cornerstone of curative treatment for breast cancer, involving both the breast and axillary areas. The main surgical options for the breast include total mastectomy or breast-conserving surgery, while axillary surgery may involve axillary clearance or sentinel lymph node biopsy.

1. Breast Surgery

Both total mastectomy and breast-conserving surgery have been shown to provide similar overall survival outcomes.

• Total Mastectomy: This procedure involves removing the entire breast, including the skin and nipple-areola complex. Breast reconstruction can be performed either at the same time or later.
• Breast-Conserving Surgery: In this procedure, only the cancerous tissue and a rim of adjacent healthy breast tissue are removed, preserving the rest of the breasts. Radiotherapy is typically required afterwards. This approach is commonly used for early-stage breast cancer.

2. Axillary Surgery

Axillary surgery is usually performed alongside breast surgery and provides additional information to help determine the cancer’s stage and formulate subsequent adjuvant treatment plan.

• Axillary Clearance: This procedure removes all lymph nodes from the armpit and is indicated when cancer has spread to this region. A possible complication is lymphedema, or swelling of the upper limb, due to disruption of the lymphatic system.
• Sentinel Lymph Node Biopsy: This procedure removes the sentinel lymph node, which is the first node to which cancer cells are likely to spread. It is now the standard procedure for patients with clinically node-negative breast cancer and has the advantage of reducing the risks of lymphedema and arm complications, while providing survival outcomes comparable to axillary clearance.

Radiotherapy

Radiotherapy involves the use of ionizing radiation to destroy cancer cells and reduce the risk of recurrence. It is often administered after breast-conserving surgery to minimize the chance of the cancer returning. In some cases, it is also given after total mastectomy, especially for larger cancers or when there is involvement of the skin, chest wall or lymph nodes.

Chemotherapy

Chemotherapy involves the use of cytotoxic drugs that kill fast-growing cells, including cancer cells. It is commonly used as an adjuvant therapy following surgery to kill any remaining cancer cells and reduce the risk of recurrence. It can also be used as neoadjuvant therapy to shrink cancers before surgery. Chemotherapy drugs target different phases of the cell cycle, but unfortunately, they cannot distinguish between cancerous and healthy cells, leading to side effects such as hair loss, mouth sores, and increased susceptibility to infections. These side effects are usually temporary as healthy cells recover.

Hormone Therapy

Around 60-70% of breast cancers are hormone receptor-positive, meaning their growth is driven by hormones like estrogen and progesterone. The two most common types of hormone therapy are selective estrogen receptor modulators and aromatase inhibitors.

• Selective Estrogen Receptor Modulators (SERMs), such as Tamoxifen, block estrogen receptors on breast cancer cells, preventing estrogen from stimulating their growth. Tamoxifen is used for both pre-menopausal and post-menopausal women. Possible side effects include menopausal symptoms, deep vein thrombosis, stroke, thickening of the endometrial lining and endometrial cancer.
• Aromatase Inhibitors (AI), such as Letrozole, Anastrozole, and Exemestane, work by blocking the enzyme aromatase, which converts androgens into estrogen, thus limiting estrogen’s effect on cancer cells. AIs are used only in post-menopausal women. Side effects may include menopausal symptoms, joint pain, and an increased risk of osteoporosis.