One problem has been the edge effect, the appearance of partial blockages of the coronary artery at either edge of the radiation field (the area treated with radiation.) This edge effect lesion, which takes on the appearance of a bar bell or a "candy-wrapper" when visualized with an angiogram, is itself a form of restenosis, and represents a significant and difficult-to-treat adverse result. The cause of these edge effect lesions is controversial, but they are said to result when the radiation is inappropriately placed (the so-called geographic miss.)
Even more disturbing is the observation that patients who receive intra-coronary radiation appear to have an increased incidence of late coronary artery stenosis. Typical restenosis after angioplasty or stenting occurs within 6 months of the procedure. (This is the type of restenosis effectively treated by radiation.) But the late stenosis following intra-coronary radiation apparently can occur years after treatment. These late blockages can lead to myocardial infarctions (heart attacks) or death. (The reported incidence of late blockages following intra-coronary radiation has varied between 7% and 14%, but no truly long-term follow-up has been completed.)
At least some of these late coronary artery occlusions appear to be due to thrombosis. (There are theoretical reasons why radiation might make coronary arteries more prone to thrombosis for a prolonged period of time.) If this is the case, then perhaps long-term anticoagulation will make this problem less severe than it now appears to be, but at the moment this problem is greatly limiting the usefulness of brachytherapy.
In addition to these documented problems with brachytherapy, other potential problems are possible. Radiation may weaken the walls of the coronary artery, and produce an aneurysm (ballooning out of the arterial wall), a potentially hazardous condition. Radiation-induced coronary artery disease (that is, coronary artery blockages) can occur after radiation for cancer therapy, for instance, and this side effect peaks at an average of 7 years after radiation. Some experts have speculated that the incidence of radiation-induced coronary artery blockage following intra-coronary radiation may take a similarly long time to become manifest. (The longest reported follow-up after intra-coronary radiation has been about 3 years.)
Should you consider receiving brachytherapy?Given all known and potential problems with this new procedure, intra-coronary radiation should be used in a very limited fashion until much more is learned about it. Brachytherapy, for now at least, should be reserved for desperate patients, those in whom there truly are no other good options, and whose situation is so grim that contemplating the threat of late restenosis (and thus of late heart attacks or death) is a luxury.
Given the problems with brachytherapy, and the inconvenience and expense of organizing a hospital to begin using it, it is not surprising that the advent of drug-coated stents has relegated brachytherapy to almost an afterthought during the past few years. Brachytherapy may still be useful in appropriate patients, but the typical patient with coronary artery disease will never be faced with the decision of whether brachytherapy ought to be considered.