What are risks of the cancer drug herceptin (trastuzumab)?

Several: Herceptin (trastuzumab) is remarkably well tolerated. The most common side effect is a decline in the pumping ability of the heart (called the left ventricular ejection fraction), possibly leading to congestive heart failure. Thus, people getting Herceptin (trastuzumab) should have an echocardiogram done before, and about every 3 months while on herceptin (trastuzumab). Most of the time, the heart recovers after the Herceptin (trastuzumab) is stopped.

Heart failure: About 4% of women treated with Herceptin (trastuzumab) develop some weakness in their heart as measured by a muga test. This decrease in heart function is reversible when the drug is stopped. Other side effects of Herceptin (trastuzumab) can include allergic reaction, fatigue, headache and diarrhea. Most of my patients have no side effects!