Biological therapy for breast cancer uses the body's immune system or hormonal system to treat cancer cells. This causes less harm to healthy cells: Side effects from biological therapy aren’t as bad as from better-known treatments like chemotherapy.
One type of biological therapy uses antibodies to attack cancer cells or block them from growing. Antibodies are a part of the immune system made by special white blood cells. They can also be made in a lab and given as medicine.
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Another type of biological therapy uses drugs made of small molecules that interrupt signals that cancer cells need to grow.
HER2-Positive Breast Cancer
One example of a man-made antibody is trastuzumab (Herceptin). Herceptin is believed to stop cancer cells from growing in three ways:
It sticks to special receptors on cancer cells, stopping them from growing.
It signals the body's immune system to attack cancer cells.
It can improve the effectiveness of chemotherapy.
But Herceptin works only if the patient has the HER2 gene in her cancer cells. About 30% of breast cancer patients have this gene; they are called "HER2-positive."
Herceptin is the standard treatment for HER2-positive breast cancer, and it's used in combination with one of the drugs known as taxanes (Abraxane, Taxol, and Taxotere).
Pertuzumab (Perjeta) is another antibody used to treat HER2-positive breast cancer. It's used in combination with Herceptin and Taxotere.
Another medication, ado-trastuzumab emtansine (Kadcyla), combines the antibody in Herceptin with a chemotherapy drug. It's used in patients with HER2-positive, metastatic breast cancer who were previously treated with a combination of Herceptin and a taxane.
One disadvantage of antibody treatment is that it is generally available only by injection. Small-molecule treatment can be taken in a pill.
Lapatinib (Tykerb) is an example of a small-molecule drug. It's used in combination with chemotherapy to treat some advanced cases of HER2-positive breast cancer. It’s often used when other cancer medications have been tried and weren't successful.
HER2-Negative Breast Cancer
Women who don’t have the HER2 gene are called "HER2-negative." These women need different cancer treatments than HER2-positive women.