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Study: Cardiovascular Drug Captopril May Limit Radiation Damage to Lungs and Heart in Cancer Patients

Mayo Clinic interested in new animal data (Apr. 21)

Unavoidable damage caused to the heart and lungs by radiotherapy of tumors in the chest may be limited by the administration of an angiotensin-converting enzyme (ACE) inhibitor, a drug commonly used in the treatment of cardiovascular disease, according to researchers in the Netherlands. The new findings were presented at the 2nd Forum of the European Society for Radiotherapy and Oncology (ESTRO), held in Geneva, Switzerland.

Sonja Van der Veen, MSc, and her colleagues investigated whether the use of an ACE inhibitor could protect against early radiation-induced lung toxicity (RILT). Previous studies had shown that damage to blood vessels can play an important role in the development of RILT. The researchers irradiated the heart and lungs of rats and administered the ACE inhibiter captopril immediately after treatment. The rats’ lung functions were then measured every 2 weeks.

“After eight weeks, when early lung toxicity is usually at its height, we found that captopril improved the rats’ heart and lung functions, but we were surprised to find that this only occurred when the heart was included in the irradiation field,” Van der Veen said. “This was not due to protection of the lung blood vessels, which were equally damaged with or without captopril. So we investigated further and found that the captopril treatment improved the heart’s function and decreased the level of fibrosis in the heart soon after irradiation. So these new findings show that ACE inhibition decreases RILT by reducing direct acute heart damage.”

Irradiating the heart leads to the development of fibrosis, which stiffens the organ, and this in turn inhibits the relaxation of the left ventricle, the researchers said. Because of this effect, blood flow from the lungs into the heart is hindered, and this can cause pulmonary damage. However, after treatment with captopril, the researchers observed an improvement in ventricular relaxation in the rats’ irradiated hearts.

Van der Veen and her colleagues are collaborating with researchers at the Mayo Clinic in Rochester, Minnesota, to design a randomized clinical trial in which patients who are treated with radiation to the thoracic area, including the heart, will be treated with either an ACE inhibitor or placebo after irradiation.

Most women with breast cancer receive high doses of radiation to the heart, and this is known to increase the risk of heart disease. A recent study has shown that for each Gray (Gy) of radiation, there is a 7.4% increase in the occurrence of a subsequent major coronary event.

Source: ESTRO; April 21, 2013.

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