Potentially Less Toxic Adjuvant Chemotherapy for Women with Breast Cancer
Name of the Trial
Phase III Randomized Study of Docetaxel and Cyclophosphamide Compared to Anthracycline-Based Chemotherapy in Treating Women with HER2-Negative Breast Cancer (NSABP-B-49). See the protocol summary.
Dr. Patrick Flynn, National Surgical Adjuvant Breast and Bowel Project
Why This Trial Is Important
Women with early-stage breast cancer usually undergo surgery to remove the tumor and surrounding tissue (lumpectomy) or the whole breast (mastectomy). Surgery is often followed by adjuvant, or postoperative, therapy that may include radiation therapy (especially for women who choose lumpectomy) and endocrine therapy (if the tumor cells test positive for hormone receptors). Women whose tumor cells produce greater than normal amounts of the receptor protein HER2 may also be treated with a drug that targets that protein. Moreover, women at high risk of cancer recurrence often receive adjuvant chemotherapy.
Over the years, doctors have made considerable progress in determining which women with resected breast cancer are more likely to experience a recurrence. One indicator is the presence of cancer cells in the lymph nodes near the affected breast. This is called lymph node-positive breast cancer. However, some women with lymph node-negative breast cancer may also face an increased risk of recurrence if their tumor is large and/or their tumor cells are hormone receptor negative, high grade, or have a gene expression profile indicative of high recurrence risk.
Although adjuvant chemotherapy has proven helpful in delaying and preventing the recurrence of breast cancer, it comes with a risk of serious side effects. For example, the drug doxorubicin has long been used in combination chemotherapy for women with high-risk breast cancer. This drug belongs to a class of drugs called anthracyclines, which are known to cause or exacerbate heart problems in cancer patients. Because heart disease is the most common cause of death in older women and breast cancer occurs predominantly in postmenopausal women, the cardiac risks of doxorubicin must be taken into account when planning a patient’s treatment.
Clinical trials conducted in the 1980s and 1990s showed that anthracycline-based chemotherapy performed better than combination chemotherapy that did not include an anthracycline. However, doctors wonder if anthracyclines are still necessary in more modern combination chemotherapy regimens that include drugs such as docetaxel or paclitaxel, which belong to another class of drugs called taxanes. Although taxanes also cause side effects, they are not known to damage the heart.
In this phase III trial, women with resected HER2-negative breast cancer that has either spread to nearby lymph nodes or has characteristics associated with a high risk of recurrence will be randomly assigned to receive one of four anthracycline-based chemotherapy regimens or six courses of docetaxel and cyclophosphamide. Doctors want to see if the combination of docetaxel and cyclophosphamide will be as effective in preventing breast cancer recurrence as commonly used regimens that also include the anthracycline doxorubicin.
“In this study, we’re primarily trying to figure out if we can eliminate the use of doxorubicin and the associated risk of cardiac toxicity and still achieve the same cure rate,” Dr. Flynn said. “As many as 50 percent of women diagnosed with nonmetastatic breast cancer will fall into this group of patients with intermediate-to-high recurrence risk, and, historically, we’ve seen about 3 to 5 percent of women treated with adjuvant doxorubicin experience serious cardiac side effects, often years after their breast cancer treatment has ended,” he added. “So, if we can eliminate doxorubicin without compromising the effectiveness of treatment, we may be able to spare a lot of women from the risk of treatment-related heart damage.”