Unavoidable damage caused to the heart and lungs by radiotherapy treatment of tumors in the chest region can be limited by the administration of an ACE inhibitor, which is a drug commonly used in the treatment of cardiovascular disease, according to new research. This research was presented at the 2nd Forum of the European Society for Radiotherapy and Oncology (ESTRO), which was held April 19-23 in Geneva, Switzerland.
Common cancers such as breast, esophagus, lung, and Hodgkin’s lymphoma are frequently treated with radiotherapy, but the radiation dose that can be given safely is limited by the sensitivity of the healthy lung tissue which is also irradiated. The lung is a particularly complex and sensitive organ and strategies for protecting it from radiotherapy damage, apart from limiting the dose given and, therefore, the efficacy of the treatment, are currently few.
Dr. Sonja Van der Veen, MSc, from the University Medical Centre, Groningen, the Netherlands, said that she had set out with colleagues to see 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, so the researchers irradiated the lungs, heart, or 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 8 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,” said Van der Veen. “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.”
Rats were chosen for the study because, unlike mice, they are big enough for researchers to be able to irradiate different part of the lungs and heart. The researchers believe that ACE inhibition works in a similar way in both animals and humans.
Much progress has been made in radiation treatment over recent years, but in breast cancer, for example, most women still receive high doses to the heart, and this is known to increase the risk of heart disease. A recent study has shown that for each gray of radiation, the risk of occurrence of a subsequent major coronary event increases by 7.4%.
“Given that most women will receive a dose of between 1 and 5 gray, and that the dangers are even greater for women with existing cardiac risk factors or coronary disease, this is still a big problem,” said Van der Veen.