**2.3 Cancer radiation treatment related cardiovascular injury**

Additional cancer therapy related adverse cardiovascular effects are not necessarily associated with pharmaceuticals of any kind and can take quite a long time for the association to become evident. In the WECARE prospective clinical trial, women receiving radiation to treat Stage 1 or Stage 2 breast cancer, 10.5% of those receiving left-sided radiation developed coronary artery disease over then next 27 years, nearly double the incidence when compared to those who received right-sided radiation (5.8%). Further, in those patients who were under age 40 at the time of treatment, 5.9% went on to develop heart disease, compared to none in the right-sided radiation treatment group [68]. The association is presumed to relate to the relative position of the underlying cardiac structures predominantly in the left thoracic compared to the right, with coronary artery disease presumed to be the result of direct injury to the coronary arteries. The association has been suggested previously [69] is consistent with findings from a meta-analysis of smaller cohorts [70], and in older patients with a specific subset of breast cancer (estrogen positive) [71]. It remains unclear whether the vascular injury hypothesis is correct, or if the disease progression/complication rate (restenosis, heart failure, arrhythmia) following the incident cardiovascular events also were worse. Perhaps what is becoming increasingly clear is that there is substantial potential for cardiovascular events as a consequence of successful management of other disease processes and heightened routine surveillance of cardiovascular end points may be warranted, even when direct cardiovascular symptoms are not immediately evident.
