Targeted therapy for breast cancer in men

As researchers have learned more about the gene changes in cells that cause cancer, they have been able to develop newer drugs that specifically target these changes. These targeted drugs work differently from standard chemotherapy (chemo) drugs. They often have different (and less severe) side effects.

Drugs that target the HER2/neu protein

Trastuzumab (Herceptin): Trastuzumab is a type of drug known as a monoclonal antibody, a man-made version of a very specific immune system protein. It attaches to a growth-promoting protein, HER2/neu (or just HER2), which is present in larger than normal amounts on the surface of the breast cancer cells in some patients. Breast cancers with too much of this protein tend to grow and spread more aggressively. Trastuzumab can help slow this growth and may also stimulate the immune system to more effectively attack the cancer.

Trastuzumab is given as an injection into a vein (IV), usually once a week or at a larger dosage once every 3 weeks. The optimal length of time to give it is not yet known, but it is often given for up to a year.

In women, trastuzumab is used (along with chemo) as adjuvant therapy for HER2-positive cancers to reduce the risk of recurrence. Using trastuzumab along with chemo has become standard adjuvant treatment for these cancers. This drug has not been tested as an adjuvant treatment in clinical trials in men (because there are too few men with breast cancer to study), but it might still be helpful for men with HER2-positive cancers.

Trastuzumab is also used to treat HER2-positive advanced breast cancers that return after chemo or continue to grow during chemo. Treatment that combines trastuzumab with chemo may be more effective than chemo alone in some patients. If a cancer gets worse while on trastuzumab and chemo, often the trastuzumab is continued and the chemo is changed.

Compared with chemo drugs, the side effects of trastuzumab are relatively mild. These occur rarely and may include fever and chills, weakness, nausea, vomiting, cough, diarrhea, and headache. These side effects are less common after the first dose.

A more serious potential side effect is heart damage leading to a problem called congestive heart failure. For most (but not all) people, this effect is temporary and improves when the drug is stopped. The risk of heart problems is higher when trastuzumab is given with certain chemo drugs such as doxorubicin (Adriamycin) or epirubicin (Ellence). For this reason heart function is checked regularly during treatment with trastuzumab. Major symptoms are leg swelling, shortness of breath, and severe fatigue. People having these symptoms should call their doctor right away.

Pertuzumab (Perjeta™): Like trastuzumab, pertuzumab is a monoclonal antibody that attaches to the HER2 protein. It seems to target a different part of the protein than trastuzumab does. This drug is used to treat advanced breast cancer. When given along with docetaxel (Taxotere) and trastuzumab to patients who have not yet received chemo for their advanced breast cancer, it has been shown to cause tumors to shrink or stop growing for about 6 months longer than giving docetaxel and trastuzumab alone.

This drug is given as an infusion into a vein every 3 weeks. When given with trastuzumab and docetaxel, common side effects included diarrhea, hair loss, nausea, fatigue, rash, and low white blood cell counts (sometimes with fever). Many side effects, such as hair loss, nausea, and fatigue occur at about the same rate as in those who get just docetaxel and trastuzumab. Although so far it has not been shown to affect heart function, there is concern that it can, so it cannot be given to patients with poor heart function. As with trastuzumab, your doctor will check tests of heart function every few months while you are treated with this drug.

Lapatinib (Tykerb): Lapatinib is another drug that targets the HER2 protein. This drug is given as a pill, most often along with the chemo drug capecitabine (Xeloda). It is used to treat advanced, HER2-positive breast cancer that is no longer helped by chemotherapy and trastuzumab. It is also being studied as an adjuvant therapy in HER2-positive patients, but at this time is only used for advanced breast cancer. It is often given with chemo, but may be given alone or with trastuzumab.

The most common side effects with this drug include diarrhea, rash, and hand-foot syndrome (hand-foot syndrome was discussed in the section “Chemotherapy for breast cancer in men”). Diarrhea is a common side effect and can be severe, so it is very important to let your health care team know about any changes in bowel habits as soon as they happen. In rare cases lapatinib may cause liver problems or a decrease in heart function (that can lead to shortness of breath), but this seems to go away once treatment is finished.