Herceptin (trastuzumab) is remarkably effective in treating advanced (i.e., metastatic) breast cancer that is HER-2-positive (approximately 30 percent of cases). It has been shown to reduce the odds of recurrence and mortality in these patients by approximately one half and one third, respectively. When first presented at the Annual Meeting of the American Society of Clinical Oncology in 2005, the results were called ?astonishing.?

On the other hand, it has also been known that Herceptin can cause heart problems in some patients. In a new study published in the August 14 issue of The Journal of Clinical Oncology, it was found that over an average time of 32 months, 28 percent of patients receiving Herceptin had some form of cardiac toxicity. The good news is that all but three patients had improved cardiac function after discontinuing Herceptin and treated for their heart problems. In fact, after treatment, patients could resume Herceptin treatment (with appropriate heart monitoring).

Because it has been known for several years that Herceptin could cause heart problems, the FDA approved prescribing information already states: that all patients should have a heart function analysis done prior to and over the course of Herceptin administration. What is new in the study mentioned above is that the occurrence of heart problems may be more frequent than originally thought.

What should you do? If you have completed Herceptin treatment without any symptoms, you do not need to do anything. If you are considering starting Herceptin treatment, make sure that you tell your doctor about any history of prior heart disease, diabetes or prior chest radiation. In addition, you should feel comfortable in raising the issue of heart problems with your doctor. For each patient, there will be a different risk to benefit ratio depending on that patient's particular medical history and condition. You should also ask to have your heart function tested prior to receiving the drug. For the majority of patients, the benefits of Herceptin will far outweigh the risk of developing heart problems (in appropriately selected and monitored patients).

If you are currently taking Herceptin, you should determine whether you had your heart tested prior to starting the drug. If not, such testing should be performed. You should also make sure that your prescribing physician is aware of any prior history of heart problems, diabetes or chest radiation. Determine how your heart will be monitored over time. Discuss with your doctor the types of symptoms you should report that could indicate decreased heart function.

With appropriate knowledge, many drug-related side effects can be either avoided or caught early. But the knowledge needs to be appropriately communicated between patient and physician.