What is Breast Cancer?
Breast cancer is a very common malignancy originating from breast tissue in women. The condition has a strong genetic basis and is frequently observed in close relatives. Patients may have a palpable breast mass, enlarged lymph nodes in the armpits (axilla), breast pain, dimpling of the skin, or nipple abnormalities. Asymptomatic individuals may also be detected by routine breast cancer screening with a mammogram.
Patients with advanced disease have a poor prognosis, but screening mammography has resulted in a significant decrease in the prevalence of the condition. Despite this, breast cancer is a leading cause of cancer death and overall mortality in the United States.
What Causes Breast Cancer?
The exact cause is unclear, but it is likely related to genetic and environment factors. Risk factors for breast cancer include:
- Advanced age
- Female gender
- Caucasian race
- Obesity in postmenopausal women
- Exposure to high estrogen levels during early menarche or late menopause
- Reproductive factors - late first pregnancy, lack of breastfeeding, and never having been pregnant (nulliparity)
- Alcohol consumption
- Cigarette smoking
Regular exercise and a diet rich in fruits, vegetables, and lean meat (e.g., fish) can lower your risk.
How Common is Breast Cancer?
Breast cancer is an extremely common condition and typically requires referral to a breast surgeon and oncologist. The incidence in the United States is approximately 250,000 cases annually. Breast cancer also results in more than 40,000 deaths each year.
The incidence is decreasing – this is likely partially due to stoppage of estrogen replacement therapy in postmenopausal women. Mortality rates are also declining likely as a result of improved breast cancer screening.
Signs and Symptoms
It is frequently detected in asymptomatic women due to increasing compliance with mammography and breast cancer screening. Some patients are diagnosed due to abnormal symptoms and signs that typically include:
- Breast mass
- Breast discomfort or pain
- Axillary (armpit) mass
- Nipple retraction or abnormalities
- Dimpling of the skin “peau d’orange” – due to skin swelling
Breast masses are most frequently located in the upper-outer quadrant of the breast. They are often firm, irregular, and fixed during palpation of the breast tissue. Regional lymph nodes in the armpit (axilla) are often affected first during metastasis. Other lymph nodes in the chest, head, and neck may also become involved.
Patients with distant metastatic disease may develop bone pain in the back or leg, liver abnormalities, and lung symptoms (e.g., cough, difficulty breathing).
It is diagnosed by pathologic confirmation of tissue demonstrating carcinoma (malignant epithelial cells) on biopsy.
Asymptomatic women who are incidentally found to have a breast mass on routine mammography typically undergo breast biopsy guided by mammogram (stereotactic biopsy) or ultrasound. Those that have a breast mass typically receive fine-needle aspiration or core needle biopsy of the lesion. Individuals with quickly progressive lesions that are tender with signs of thickening and hardening of the skin require a full-thickness skin biopsy.
Tissues are analyzed for expression of certain receptors that affect prognosis and treatment. These include the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factors (HER2) receptor. Genetic studies are also occasionally performed.
Breast cancer is staged based on the size of the tumor, presence of regional lymph node involvement, and whether or not there is distant metastasis (TNM staging system). Patients with distant metastasis have a poor prognosis.
Breast Cancer Treatment and Medication
Breast cancer is treated based on the stage of disease. This article focuses on the treatment of early or locally advanced breast cancer.
Patients with early-stage breast cancer usually receive lumpectomy or mastectomy to the breast and regional nodes with or without radiation treatment. Sometimes, adjuvant systemic therapies are offered as well depending on characteristics of the tumor. Patients with more locally advanced disease often require neoadjuvant chemotherapy, surgery, radiation, and endocrine therapy. The discussion of chemotherapy is beyond the scope of this article.
Endocrine therapy can be an effective systemic treatment in hormone-receptor positive breast cancer. Premenopausal women are often treated with ovarian suppression, selective estrogen receptor modulators, and aromatase inhibitors.
- Ovarian suppression may be performed via ablation (e.g., oophorectomy, ovarian irradiation) or with gonadotropin-releasing hormone (GnRH) agonists such as Zoladex (goserelin).
- Selective estrogen receptor modulators commonly include Nolvadex (tamoxifen) and Fareston (toremifene).
- Aromatase inhibitors include Femara (letrozole), Arimidex (anastrozole), and Aromasin (exemestane) – these work by blocking conversion of androgens to estrogen.
In postmenopausal women, agents such as CDK 4/6 inhibitors plus Femara (letrozole), Faslodex (fulvestrant), or aromatase inhibitors are typically used. CKD 4/6 inhibitors include Ibrance (palbociclib) or Kisqali (ribociclib).
Patients with HER2+ responsive disease typically receive targeted therapy with Herceptin (trastuzumab).
- Fisher B, Anderson S, Bryant J, et al. Twenty-year follow-up of a randomized trial comparing total mastectomy, lumpectomy, and lumpectomy plus irradiation for the treatment of invasive breast cancer. N Engl J Med 2002; 347:1233. - https://www.nejm.org/doi/full/10.1056/NEJMoa022152
- Prum BE Jr, Veronesi U, Cascinelli N, Mariani L, et al. Twenty-year follow-up of a randomized study comparing breast-conserving surgery with radical mastectomy for early breast cancer. N Engl J Med 2002; 347:1227. - https://www.ncbi.nlm.nih.gov/pubmed/12393819
The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.