A medical oncology perspective
Breast cancer is the most common cancer occurring in women (excluding skin cancer) and the second-most common cause of death from cancer (after lung cancer). Men can also develop breast cancer, but it is rare and accounts for less than 1 percent of breast cancer diagnosis. Most breast cancers start in the ducts or lobes of the breast. If the disease has spread outside of the duct and into the surrounding tissue, it is called an invasive or infiltrating ductal or lobular carcinoma. Disease that has not spread is called in situ. Breast cancer can spread when cancer cells move to other sites in the body through the blood vessels and/or lymph nodes. This process is called metastasis. The most common sites of metastases are to the regional lymph nodes of the axilla and neck, as well as to bone, lungs, liver and brain.
As a medical oncologist, my job is to plan the care of breast cancer patients together with surgeons, radiologists, pathologists, radiation oncologists and primary care doctors. In the treatment of breast cancer, a medical oncologist can use hormone therapy, chemotherapy and targeted therapies. Hormone therapy helps to manage tumors that test positive for either estrogen or progesterone receptors. These tumors use hormones to fuel growth, and blocking these hormones limits tumor growth. Tamoxifen is a drug that blocks estrogen from binding to breast cancer cells, aromatase inhibitors decrease the amount of estrogen in postmenopausal women by blocking an enzyme named aromatase, which is needed to make estrogen. For women with ER-positive cancers who have not yet undergone menopause, an additional treatment may include suppressing ovarian function. This can be done temporarily with drugs called luteinizing hormone releasing analogies (LHRH) or by surgical removal of the ovaries. Hormone therapies can be used as an adjuvant treatment (in women with resected breast cancer to decrease the risk of recurrence), for chemoprevention (decreasing the chances breast cancer will occur in women with increased risk) and also for treatment of advanced, metastatic disease.
Chemotherapy is the use of drugs to kill cancer cells. Chemotherapy can be given intravenously or by mouth and spread by the bloodstream targeting cancer cells throughout the body. Chemotherapy is usually given in cycles, using specific treatment schedules of drugs given at repeating intervals for a specific number of times. Chemotherapy can be given before surgery to reduce the size of a breast cancer (neoadjuvant therapy), after surgery to reduce the risk of recurrence (adjuvant therapy) or in the treatment of metastatic disease. The side effects of chemotherapy depend on the individual and the drug and dose used, but can include fatigue, hair loss, increased risk of infection, nausea and vomiting, loss of appetite, and diarrhea. These side effects usually go away once treatment is finished. Rarely, long-term side effects can occur, such as heart damage, nerve damage or secondary cancers.
Targeted therapy is a treatment that targets specific genes, proteins or the tissue environment that contributes to cancer growth and survival. There are currently two main classes of biologically targeted therapy approved in breast cancer treatment, one that targets the HER2 molecule (trastuzumab and lapatinib) and one that targets blood vessel formation or angiogenesis (bevacizumab). Other drugs target osteoclasts and hence block bone destruction in patients with cancer that has metastasized to the bone. These include bisphosphonates (zolendronic acid and pamidronate) and RANK ligand inhibitors (denosumab).
After treatment for breast cancer ends, a follow-up plan must be developed. This will include regular physical examinations and medical tests including screening mammograms. Women recovering after breast cancer treatments may have persistent symptoms, such as cancer-related fatigue and a drop of cognitive function (also called chemobrain). Other potential problems after cancer treatments include the development of lymphedema (swelling of the hand or arm); this may be prevented by physical therapy and weightlifting exercises.
Women recovering from breast cancer are encouraged to follow established guidelines for good health, including increased physical activity; a diet rich in fruits and vegetables and low in animal fats; and maintaining a healthy weight. Also, smoking cessation is encouraged in active smokers, and moderate consumption of alcohol is also recommended. Women must continue to follow recommended cancer screenings.
In summary, a large number of women and some men face a diagnosis of breast cancer every year. Most of them are able to survive the disease through a combination of treatments that include surgery, radiation therapy, hormone therapy, chemotherapy and targeted therapy. It is the job of medical oncologists to accompany our patients on their journey with this illness. This is, unfortunately, not a battle that every patient wins, and it is estimated that there will be 39,970 deaths this year from breast cancer. This challenges us to continue improving our treatments, as well as focus on early detection and prevention.