Drug Therapy for Breast Cancer

Many women with breast cancer receive drug therapy in addition to surgery. Drug therapy for breast cancer can include chemotherapy, newer biological drugs, hormone-blocking agents and other medications.

Medical oncologists in the Breast Cancer Program specialize in treating women with breast malignancies. They work with surgeons, radiation oncologists and other physicians to create drug therapy strategies that are completely coordinated with the patient’s overall care plan.

Adjuvant Therapy

Even after tumor tissue has been surgically removed and the patient has received radiation therapy, it is possible that microscopic cancer cells have spread to other parts of the body. Many breast cancer patients receive adjuvant drug therapy — drugs given post-operatively to kill any metastatic cancer cells and decrease the chance of cancer recurrence.

Preoperative Drug Therapy

Drug therapy before surgery, also called neo-adjuvant therapy, is being used for a growing number of breast cancer patients. The goal of neo-adjuvant drug therapy is to reduce the size of the tumor before surgery. For some women, shrinking the tumor may make a breast-conserving surgery possible (a lumpectomy as opposed to a mastectomy).

For other women, reducing the size of the tumor could be key to making surgery feasible at all. Giving drugs pre-operatively can also help medical oncologists find out how sensitive a patient’s tumor is to drug therapy, information that could prove useful when making later treatment decisions.

Drug Therapies for Metastatic Disease

Breast cancers that have spread to other parts of the body are treatable, and drug therapy can extend survival for a significant number of patients. Drug options for metastatic disease include several of the agents that are also used to treat patients with earlier-stage breast cancer. In addition, some patients may benefit from receiving bevacizumab (Avastin), a biological drug that slows the growth of cancer by inhibiting the development of new blood vessels within tumors. Drugs that block bone metastases are also available.

Tailoring Drug Therapy to Tumor Types

Medical oncologists are increasingly able to individualize drug therapies based on the molecular characteristics of tumors. By identifying certain genes that are present at higher levels within the cells of a patient’s tumor, physicians can ascertain how the tumor might behave and what drugs might be beneficial in fighting the cancer.

It is important to note that tumor gene profiling examines the abnormal genes present in a patient’s tumor. It is different from BRCA testing that looks at a woman’s normal cells to determine her genetic risk of developing breast cancer.

At present, tumor gene profiling can guide drug therapy decision-making for a handful of known tumor types:

HER2-Positive Tumors

HER2 is a protein that is present in some normal cells within the human body. In normal cells, HER2 plays a key role in cell growth. In approximately 25 percent of breast cancers, HER2 is present at abnormally high levels, which causes the tumor to grow rapidly. Women with this type of breast cancer can benefit from taking biological drugs that block the action of HER2. Trastuzumab (Herceptin) is a HER2-inhibitor used in combination with chemotherapy for women whose cancer is still confined to the breast. Lapatinib, a second-generation HER2 inhibitor, is approved for women whose cancer has spread to other parts of the body.

Hormone-Sensitive Tumors

In approximately 80 percent of breast cancers, estrogen and progesterone receptors are present in the cells of the tumor. If these receptors are present, it is likely that the tumor requires hormones for cell growth and that hormone-blocking agents will inhibit the cancer. One medical option is tamoxifen, a drug that binds to the cancer cell’s estrogen receptors, preventing the tumor from receiving the hormone. 

Post-menopausal women can also receive aromatase inhibitors, drugs that block the body’s production of estrogen. Drug therapy can also be used to “turn off” the ovaries, and for some women oophorectomy (the surgical removal of the ovaries) is an option.

Tumor Gene Profiling to Guide Treatment Decisions

Some tumor gene tests can help physicians understand which patients would likely benefit from certain therapies and which would not. For example, patients with breast cancer that has not spread to the lymph nodes have a generally low risk of recurrence. Yet, for a significant number of these women, the cancer will return. A test called Oncotype DX profiles 21 genes in the cancer tumor to help distinguish patients with a truly low risk of recurrence from those who need and would benefit from chemotherapy.