How Does Brachytherapy Work?

Angioplasty and stenting have revolutionized how to treat coronary artery disease, but these therapies have introduced a new kind of problem into the mix. This is the problem of restenosis — recurring blockage at the site of treatment. In the early 2000s, brachytherapy, or coronary artery radiation therapy, became a promising new treatment for restenosis. But while brachytherapy was (and still is) quite effective for restenosis, it now has been largely supplanted by the use of drug-eluting stents.

Restenosis after angioplasty or stenting is caused by the excessive growth of tissue at the site of treatment. It is caused by an excessive healing reaction, producing a proliferation of the “endothelial” cells that normally line the blood vessels. This tissue growth can gradually re-occlude the artery. 

Brachytherapy can treat restenosis by killing excess cells and preventing further tissue growth.

How Is Brachytherapy Applied?

Brachytherapy is administered during a special heart catheterization procedure. The radiation itself is delivered by a special type of catheter designed to apply radiation from within the coronary artery. The catheter is passed into the coronary arteries and across the blockage being caused by restenosis. Once the targeted area's “bracketed” by the catheter, the radiation is applied.

Two varieties of radiation can be used: gamma radiation and beta radiation. Both kinds of radiation are relatively cumbersome to use, and require the presence of special equipment in the lab, adopting special precautionary procedures, and specially trained individuals, usually including a radiation oncologist. Cardiologists who have used brachytherapy agree that a key to success is the experience of the operator. These are complex procedures that require more than the usual expertise of the typical interventional cardiologist.

Effectiveness

Clinical studies have shown that brachytherapy works well at relieving restenosis in coronary arteries, and in reducing the risk of further restenosis. In addition, studies seem to show that patients with a high risk of restenosis—(such as people with diabetes)—seem to gain the most benefit from radiation therapy.

Problems 

Brachytherapy is not problem-free. One unique problem seen with brachytherapy has been the “edge effect” — the appearance of new blockages at either edge of the radiation field (the area treated with radiation). This edge effect lesion, which takes on the appearance of a barbell or a "candy-wrapper" when visualized with an angiogram, is a significant adverse result which is difficult to treat. These edge effect lesions are most likely caused by suboptimal placement of the catheter when administering the brachytherapy.

Also, patients treated with brachytherapy appear to have an increased risk of late coronary artery thrombosis (blood clot). Typically, if thrombosis occurs following angioplasty or stenting, it usually occurs within 30 days of the procedure. But late thrombosis (occurring after the initial 30 days) is seen in almost 10% of patients receiving brachytherapy. This late thrombosis commonly is associated with myocardial infarction (heart attack) or unstable angina. To help reduce this risk, blood thinners are recommended for at least a year after brachytherapy.

Why Is Brachytherapy So Rarely Used Today?

Restenosis was the biggest unsolved problem in the early days of angioplasty and stenting, and for several years brachytherapy looked like a promising way to deal with restenosis. However, it is now used only rarely.

The appearance of drug-eluting stents quickly made brachytherapy almost obsolete. Studies directly comparing the safety and effectiveness of brachytherapy to drug-eluting stents for treating restenosis showed pretty definitively that the stents give better results. Furthermore, cardiologists are comfortable placing stents, and stents do not require the inconvenience, expense, and highly specialized expertise required by brachytherapy. It did not take long for brachytherapy to largely drop off the map.

Still, brachytherapy is effective and reasonably safe and has been approved for use by the Food and Drug Administration. A few specialized centers still offer it as an option for treating restenosis.

Today, brachytherapy is generally considered an option only for patients who have had recurrent restenosis following stenting, and in whom drug-eluting stents have failed to stem the problem. To receive brachytherapy these patients need to be referred to one of the few centers still offering this kind of therapy.