Adjuvant therapy is additional treatment administered after initial surgery and radiation therapy. The goal of adjuvant therapy is to eliminate any cancer that remains after surgery or radiation therapy, thereby reducing the risk of cancer recurrence.
Despite undergoing surgery and radiation, some patients already have small amounts of cancer that have spread outside the breast. These cancer cells are referred to as micrometastases and cannot be detected with any of the currently available tests. The presence of micrometastases causes breast cancer recurrence following local treatment with surgery and/or radiation therapy. An effective treatment is needed to cleanse the body of micrometastases in order to improve a patient’s duration of survival and potential for cure.
Adjuvant therapy for early-stage breast cancer may include chemotherapy, hormonal therapy, and/or biologic therapy. In 1990, the National Institutes of Health issued a statement indicating that all women with node-negative breast cancer have a risk of cancer recurrence and treatment with adjuvant chemotherapy and hormonal therapy should be considered on an individual basis following a discussion of the potential risks and benefits of treatment with their physician.
Clinical trials have demonstrated that treatment of early-stage breast cancer with adjuvant therapy reduces the risk of recurrence and improves survival. , , Patients that have been identified as having a poorer prognosis are most likely to benefit from adjuvant therapy and should work closely with their doctor to select their optimal adjuvant therapy. This section is a discussion of the potential benefits, as demonstrated in clinical trials, of the following types of adjuvant therapy:
Chemotherapy is any treatment involving the use of drugs to kill cancer cells and is a standard adjuvant therapy for early-stage breast cancer. Cancer chemotherapy may consist of single drugs or combinations of drugs and can be administered through a vein or delivered orally in the form of a pill.
A National Cancer Institute sponsored clinical trial initiated in 1981 illustrates the benefit of adjuvant chemotherapy treatment of women with node-negative breast cancer. In this study, 536 women with node negative breast cancer were treated with surgical mastectomy alone or with surgical mastectomy plus adjuvant chemotherapy. Ten years following treatment, 73% of women treated with mastectomy and adjuvant chemotherapy were alive without evidence of cancer recurrence, compared to only 58% of women treated with mastectomy alone. Chemotherapy reduced the risk of recurrence by 37% and the chance of dying from breast cancer by 34%.
Chemotherapy options: There are many different chemotherapy drugs and combinations of drugs (regimens). The regimen consisting of cyclophosphamide, methotrexate and fluorouracil (CMF ) was the first standard combination used to treat individuals with node-negative breast cancer and has been in use for many years. CMF chemotherapy is typically administered for 6 cycles over a period of approximately 4-6 months. Some clinical studies in women with more advanced breast cancer have suggested
that including the chemotherapy drug doxorubicin in chemotherapy regimens may improve an individual’s outcome with breast cancer.
Research shows that the inclusion of the chemotherapy drug doxorubicin in adjuvant chemotherapy increases the number of women that can expect to survive without evidence of cancer compared to combination chemotherapy without doxorubicin. CAF (cyclophosphamide, doxorubicin, and fluorouracil) and AC (doxorubicin and cyclophosphamide) are also considered standard chemotherapy regimens for use in node-negative breast cancer; however, these regimens are associated with more side effects than CMF.
The taxanes are a class of chemotherapy drug that have been shown to improve cancer-free survival of women with Stage II-III breast cancer and are typically combined with AC chemotherapy in the treatment of breast cancer. They may also provide benefit in the adjuvant treatment of node-negative disease. Of the taxanes that are used in the treatment of breast cancer, Taxotere® (docetaxel) appears to be more effective than Taxol® (paclitaxel) in the treatment of patients with advanced breast cancer and is FDA-approved for the treatment of patients with locally advanced (Stage II and III) and metastatic (Stage IV) breast cancer.
Adjuvant Hormonal Therapy
Estrogen causes some cancers to grow. The breasts, uterus and other female organs are composed of cells that contain estrogen receptors. When cells that have estrogen receptors become cancerous, exposure to estrogen increases the cancer’s growth. Cancer cells that have estrogen receptors are referred to as estrogen receptor-positive (ER-positive) cancers.
The growth of ER-positive breast cancer cells can be prevented or slowed by reducing the exposure to estrogen. This is the goal of hormonal therapy for breast cancer. Hormonal therapy drugs include tamoxifen as well as a newer of drugs known as aromatase inhibitors. Aromastase inhibitors include Femara® (letrozole), Arimidex® (anastrazole), and Aromasin® (exemestane). In premenopausal women, surgical removal of the ovaries or suppression of ovarian activity may also be used to reduce estrogen exposure.
For more in-depth information about hormonal therapy, go to Hormonal Therapy for Breast Cancer .
Adjuvant Chemotherapy plus Hormonal Therapy
Researchers with the National Surgical Adjuvant Breast and Bowel Project (NSABP) have reported that the combination of adjuvant chemotherapy and hormonal therapy appears to increase survival over adjuvant hormonal therapy alone and may be the optimal treatment for women with node-negative, ER-positive breast cancer.
In a clinical trial involving over 1,500 women with node-negative, ER-positive breast cancer, patients underwent surgical removal of the cancer and half of the patients then received 5 years of hormonal therapy and the other half received 5 years of hormonal therapy plus chemotherapy. More of the women who were treated with the combination of chemotherapy and hormonal therapy lived cancer-free for 12 years or more.
Adjuvant hormonal therapy and chemotherapy in the treatment of women with node-negative ER-positive breast cancer
Hormonal therapy plus chemotherapy