Herceptin Side Effects

Herceptin has some side effects, but the good news is that it doesn't cause the hair loss and nausea associated with most chemotherapy drugs.

Mild side effects

Herceptin causes flu-like symptoms in about 40% of the women who take it. These symptoms may include fever, chills, muscle aches, or nausea. These side effects generally become less severe after the first treatment. Other side effects, including low white or red blood cell counts, diarrhea, and infections, are seen in some women receiving Herceptin in combination with chemotherapy, but are rarely seen in women taking Herceptin alone.

Serious heart side effects

Less commonly, Herceptin can damage the heart's ability to pump blood effectively. Find out more about the benefits and side effects of Herceptin. Rarely (about 5% of the time), the heart damage is bad enough that women experience stroke or life-threatening congestive heart failure—a condition in which the heart can't pump effectively. Slightly more often (about 7% of the time), Herceptin causes mild heart failure.

Women who experience mild or more serious heart damage can stop taking Herceptin and start taking heart-strengthening medications. This often brings heart function back to normal.

Heart damage can be more severe when Herceptin is given along with other chemotherapy medicines known to cause heart damage, including Adriamycin (chemical name: doxorubicin) and possibly others.

Taking Herceptin with the chemotherapy drug Taxol (chemical name: paclitaxel) does not increase your risk of severe heart damage. Studies have shown that this combination causes only slightly more mild heart damage than Herceptin alone. Women in clinical trials who are receiving Herceptin plus Taxol are being watched very closely for this effect.

Testing your heart before and during Herceptin treatment

Before starting Herceptin therapy, you should have an echocardiogram or a MUGA scan to check how well your heart is functioning.

• An echocardiogram uses sound waves to take detailed pictures of the heart as it pumps blood. For this quick test, you lie still for a few minutes while a device that gives off sound waves is briefly placed on your ribs, over your heart. There is no radiation exposure with this test.
• A MUGA (multigated blood-pool imaging) scan takes about an hour. In this test, a tiny amount of radioactive material is injected into a vein in your arm. This material temporarily hooks onto your red blood cells. You lie still while a special camera that can detect the radioactive material takes pictures of the blood flow through your heart as it beats.

When you first start taking Herceptin, your doctor might want you to have MUGA scans or echocardiograms every few months to detect any sign of heart failure. But after you've been on Herceptin for a while, you may need a heart-monitoring test only every 6 months or so. This is because heart failure is less likely to occur the longer you take Herceptin.

If you're taking Herceptin, be sure to notify your doctor immediately, or go to the nearest emergency room, if you develop any symptoms of heart failure. These symptoms include shortness of breath, difficulty breathing, a fast or irregular heartbeat, increased cough, and swelling of the feet or lower legs.

Serious lung side effects

According to Genentech, the company that makes Herceptin, 62 of the approximately 25,000 women who had taken Herceptin as of 2001 had a serious reaction to the medication. There were two types of serious reactions: allergic–like reactions and lung reactions. Symptoms of the allergic–like reactions included hives, wheezing, and trouble breathing because of swelling and muscle spasms of the airways. Lung reactions included swelling of the lung, low blood pressure, or fluid buildup around the lungs (called pleural effusions).

Fifteen of the 62 women with serious reactions ultimately died of complications from these reactions. Since approximately 25,000 women have taken Herceptin, the chance of these life–threatening reactions is quite rare, much less than 1% (15 out of 25,000). In most cases (about 75%) this reaction happened within the first 24 hours of the first dose of Herceptin. The rest of the time, it usually happened within the first week of the first dose. Only occasionally did reactions occur with the second or later doses.

The reactions are more severe if you've already had lung disease, such as asthma or emphysema, or if the breast cancer has spread significantly into your lungs.

If you are currently undergoing treatment with Herceptin and have been tolerating it well, you're very unlikely to develop these serious reactions.

Even though the severe side effects are relatively rare, your doctor should check you carefully for any heart or lung problems before starting to treat you with Herceptin. You should also be monitored closely for these serious side effects during treatment.