What is the treatment for stage I breast cancer?
Stage I breast cancers are small and have not spread to the lymph nodes or have spread to the lymph nodes only in a tiny area. While this is an early stage of breast cancer, there is a risk of such cancers recurring if not treated effectively.
Surgery is the standard treatment for early-stage breast cancers. Both breast-conserving surgery (BCS; also referred to as lumpectomy or partial mastectomy) or mastectomy may be performed, depending upon many factors, including both location of the tumor and patient preference. The lymph nodes will also be evaluated to make certain there is no spread to these areas. This can be done by either a sentinel lymph node biopsy (looking at the lymph node most likely to be the site of tumor spread) or an axillary lymph node dissection. Breast reconstruction surgery can be done either at the same time as the cancer surgery or later on.
When BCS is performed, it is most commonly followed by radiation therapy to help reduce the risk of the cancer coming back (recurring). In women over 70 years of age who have small tumors that have not spread to the lymph nodes, radiation therapy may not always be given if the tumor has been shown to express hormone receptors and hormone therapy is given.
Any additional therapy intended to improve the likelihood that the cancer will never recur is called an adjuvant therapy. Such treatment depends upon the characteristics of the tumor. If the tumor expresses hormone receptors (estrogen, progesterone), it is said to be hormone-sensitive or hormone receptor-positive. This means that hormones stimulate growth of the cancer cells, and hormone therapy is recommended. The goal of hormone therapy is to block the body's ability to make hormones or to interfere with the activity of hormones.
Two different kinds of hormone therapy may be given. Tamoxifen (Nolvadex) is a commonly used drug of the selective estrogen receptor modulator (SERM) class. These drugs bind to estrogen receptors, preventing estrogen from binding. Tamoxifen is typically prescribed for premenopausal women (and men) who have estrogen receptor-positive breast cancer. Tamoxifen therapy is given for five to 10 years. Another drug class used for breast cancer hormone therapy is the aromatase inhibitors (AI). These further reduce levels of estrogen by blocking the conversion of adrenal hormones to estrogen through the process of aromatization in the fat. Women who are postmenopausal will usually receive adjuvant hormone therapy with an aromatase inhibitor, like anastrozole (Arimidex), letrozole (Femara), or exemestane (Aromasin). Women who become postmenopausal during tamoxifen treatment may be switched to an aromatase inhibitor. Because women may stop having periods on tamoxifen, blood tests to measure hormone levels are often needed to determine whether menopause has occurred. Another option for premenopausal women, instead of tamoxifen, is taking a medication to suppress activity of the ovaries along with an AI. Bisphosphonates are a drug class that can help reduce bone loss and fractures as well as improves survival in women taking AIs for breast cancer.
Hormone therapy is one type of adjuvant therapy. Chemotherapy is another type of adjuvant therapy. For early-stage breast cancers, including stage I tumors, chemotherapy is sometimes recommended. Chemotherapy is usually recommended if the tumor is hormone receptor-negative or is HER2-positive (see below). Chemotherapy may also be recommended for an estrogen-receptor-positive tumor if the tumor is large or has an unfavorable result on a genomic profiling assay such as the Oncotype DX Breast Cancer Assay. Chemotherapy is usually given for a period of three to six months depending upon the exact regimen selected.
Tumors that overexpress the HER2 (human epidermal growth factor receptor 2) receptor are generally treated with adjuvant HER2-targeted therapy. HER2 is a normal protein that helps normal breast cells grow and divide. However, in certain breast cancers, there are too many copies of the HER2 gene, leading to overexpression of the protein and uncontrolled cell growth. These are called HER2-positive cancers. Trastuzumab (Herceptin) is an example of an anti-HER2 drug that binds to the HER2 receptors and blocks their reception of growth signals.