Targeted therapy for breast cancer

As we have learned more about the gene changes that cause cancer, researchers have been able develop newer drugs that are aimed right at these changes. These targeted drugs do not work the same as standard chemo drugs. They often have different and less severe side effects.

Drugs that target HER2

About 1 out of 5 breast cancers have too much of a protein called HER2/neu. HER2/neu is found in small amounts on the surface of normal breast cells and in large amounts on some breast cancer cells. Breast cancers that have too much of this protein are called HER2/neu-positive (or just HER2 positive). The protein makes them grow and spread faster. Certain drugs target this protein, stopping it from causing breast cancer cell growth. These drugs are:

• Trastuzumab (Herceptin)
• Pertuzumab (Perjeta^®)
• Ado-trastuzumab emtansine (Kadcyla^™)
• Lapatinib (Tykerb)

Trastuzumab and pertuzumab are monoclonal antibodies — a man-made versions of a very specific immune system protein. They are given into a vein (IV).

Ado-trastuzumab emtansine is a conjugated monoclonal antibody – a monoclonal antibody attached to a chemotherapy drug. It is also given IV.

Trastuzumab can be used to treat both early and late stage breast cancer. When used to treat early breast cancer, this drug is usually given for a year. For advanced breast cancer, treatment doesn’t stop after a year and can last a long time.

Pertuzumab can be given with trastuzumab to treat advanced breast cancer.

Ado-trastuzumab emtansine is used to treat advanced breast cancer in women who have already been treated with trastuzumab.

Lapatinib is given as pill to treat advanced breast cancer. It is most often used if the doctor thinks that trastuzumab is no longer working.

The side effects of these drugs are often mild. Discuss what you can expect with your doctor.

Some women do develop heart damage during or after treatment with the antibody drugs (trastuzumab, pertuzumab, and ado-trastuzumab emtansine). For most (but not all) women, this effect has been short-term and gets better when the drug is stopped. If you are getting one of these drugs, you should tell your doctor right away if you have any shortness of breath, swelling of the feet or legs, or trouble with physical activities.

None of these drugs should be given to women who are pregnant because they can harm and even cause death to the fetus. Women who could become pregnant need to use effective birth control during treatment.

Everolimus (Affinitor^®)

Everolimus is a type of targeted therapy that blocks a protein in cells that normally promotes their growth. By blocking this protein, it can help stop cancer cells from growing. Everolimus may also stop tumors from growing new blood vessels, which can help limit their growth. In treating breast cancer, this drug seems to help hormone therapy drugs work better.

This drug can be used along with a hormone therapy drug to treat advanced hormone receptor−positive, HER2−negative, breast cancer in women who have gone through menopause. It is meant to be used after a first hormone therapy drug stops working. Everolimus is a pill taken once a day.

Common side effects of this drug include mouth sores, diarrhea, nausea, fatigue, feeling weak or tired, low blood counts, shortness of breath, and cough. Everolimus can also affect certain lab tests, so your doctor will check your blood work at times while you are on this drug.