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Protecting the Heartby Karen Stuyck
Heart disease is one of the most common treatment-limiting side effects of cancer therapy. Monitoring patients for heart damage and managing the anticancer therapy to minimize cardiovascular complications are the keys to dealing with the problem, according to M. D. Anderson cardiologists. Preventing treatment-related heart problems in cancer patients is especially important today, said Daniel Lenihan, M.D., associate professor in the Department of Cardiology and director of clinical research in cardiology. “Cancer treatment has become so much more effective that, in many cases now, living with cancer resembles managing a chronic disease like diabetes or high blood pressure,” he said. American Cancer Society statistics indicate that the 5-year survival rate for all cancers has substantially increased in the past 20 years, from 51% for patients diagnosed between 1975 and 1977 to 66% for patients diagnosed between 1996 and 2002. “We don’t want our patients to survive cancer and then die of a heart problem that might have been avoided.” Chemotherapy and even newer biological and targeted cancer therapies can weaken a patient’s heart. A study by M. D. Anderson cardiologists, published in the June 29, 2004, issue of the journal Circulation, reviewed the effects of 29 anticancer agents and concluded that every class of cancer drugs can potentially damage the heart. One of the most problematic classes of anticancer drugs is the anthracyclines/anthraquinones, which include doxorubicin, widely prescribed for breast cancer, lymphoma, and other cancers. These drugs can cause irreversible chronic heart failure or left ventricle damage, said Edward T. H. Yeh, M.D., professor in and chair of M. D. Anderson’s Department of Cardiology. The mechanism is thought to be direct myocardial injury due to formation of free radicals. Patients given these drugs need to be closely monitored for early signs of heart problems, he said, to limit any cardiotoxicity. Other chemotherapy agents have a variety of toxic effects on the heart. If the total dose is high, cisplatin and cyclophosphamide may produce problems ranging from hypertension to chronic heart failure. Antimetabolites, such as 5-fluorouracil, can cause ischemia that, if untreated, can lead to heart attacks. The newer targeted therapies, designed to attack only cancer cells, may also cause cardiotoxicity. Monoclonal antibody drugs, such as bevacizumab, cetuximab, and rituximab, produce significant infusion reactions, such as hypertension or hypotension, in some cancer patients. Antihistamines, acetaminophen, steroids, and slow infusions may prevent or minimize such reactions. Careful monitoring for hypotension is recommended for patients who have pre-existing cardiac disease. If recognized early enough, these blood pressure changes can be easily treated, Dr. Yeh said. Recent research has provided useful information for treating these therapy-related heart problems. “Before we just recognized that people were at risk for a heart problem, but now we’ve refined who’s at risk,” Dr. Lenihan said. Cardiotoxicity can occur in any cancer patient, though elderly patients or those who already have pre-existing illnesses such as heart disease or diabetes have the highest risk. This damage to the heart can occur during treatment or months afterward. It’s important that cardiologists and oncologists work together both to prevent cardiotoxicity from occurring during cancer treatment and to treat any heart problems that do appear, Dr. Lenihan said. He and other physicians in the Cardiopulmonary Center often consult with the cancer center’s oncologists or cardiologists outside of M. D. Anderson. They may be asked to evaluate such issues as a new cancer patient’s risk of cardiovascular disease or how to minimize the effects of cancer therapy for a patient with pre-existing heart disease. Depending on the individual case, they might recommend adjusting the patient’s heart medications throughout the course of chemotherapy, since chemotherapy typically affects blood pressure. A patient’s heart treatment might also have to be changed because of impending cancer therapy. For instance, a stent should not be implanted because anticoagulants, which are necessary because clots otherwise may form in the stent, are contraindicated during chemotherapy. Instead, Dr. Lenihan said, he would probably recommend maximizing medical therapy to manage the heart problems. Other patients might require going off clopidogrel, a blood thinner, for a period of time before having cancer surgery since the drug could adversely affect their ability to clot. “The timing can be critical,” Dr. Lenihan said. “We want to minimize the time a patient is off that medication because we understand how important it is.” Educating other physicians about new management techniques to limit toxicity during cancer treatment is also vitally important, he said. He and other M. D. Anderson physicians have given presentations at the Heart Failure Society of America to inform cardiologists about guarding against heart problems during cancer treatment. Last February, the first Cardiology and Oncology Partnership symposium, held at M. D. Anderson and chaired by Dr. Lenihan, offered health professionals a comprehensive review of cardiovascular complications related to cancer therapy. A second conference will be held next May in conjunction with Memorial Sloan-Kettering Cancer Center in New York. Cardiologists and oncologists, Dr. Lenihan said, may have different perspectives or focuses, but cancer patients with heart problems can only benefit from a partnership between the two medical specialties and multi-disciplinary management of their treatment. Dr. Lenihan is also involved in research to detect cardiotoxicity after chemotherapy earlier than commonly used monitoring techniques. One of his M. D. Anderson studies used cardiology-specific blood tests—cardiac biomarkers B-type natriuretic peptide and troponin—to identify cardiotoxicity earlier than standard methods. The preliminary study will be repeated in a more definitive fashion at other institutions, Dr. Lenihan said. He is hopeful that this research will help identify chemotherapy-related heart problems “at the onset of the problem so that we can devise ways to prevent it from becoming a real issue. “Right now, we just respond to problems after they develop, but our research using biomarkers gives a mechanism to react much sooner and devise a treatment strategy to limit or prevent such toxicity.” For more information, call askMD Anderson at 1-877-632-6789 or visit www.mdanderson.org/care_centers/cardiopulmon. Other articles in OncoLog, November 2007 issue:
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