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For Release: October 24, 2000
Studies show that more than 150,000 Cardiac Patients a Year Could Benefit from New Radiation Procedure
Researchers have found that using radiation is an effective way to open blocked arteries after they were previously opened by angioplasty and stents, and keep them open, providing patients an alternative to invasive surgery.
Two radiation methods, beta and gamma, were tested in separate trials to demonstrate their efficacy.
The Stents and Radiation Therapy (START) trial, which used Beta radiation (strontium-90), was effective in treating blocked areas less than 20 mm (about one inch) - while the Gamma II trial used gamma radiation (iridium-192) and found it to be effective in treating areas up to 45 mm (almost two inches).
The triple-blinded, multi-institution START trial enrolled 476 patients from September 1998 to April 1999 and included people from 50 centers in North America and Europe. The group was composed of 313 men and 163 women. Those eligible included patients with in-stent restenosis (patients who had undergone angioplasty to unblock their artery, had a stent or a metal screen to prevent the artery from closing put in, only to have the artery block again).
Of the patients in the study, 244 received radiation while the other 232 received a placebo.
Eight months after the initial procedure, follow-up angiography was performed on 386 of the patients. Revealingly, only 14 percent of those in the beta radiation-treated group experienced restenosis, while 41 percent of those who received a placebo demonstrated reblocking of the treated artery.
Additionally, patients in the beta radiation-treated group showed a 31 percent reduction of major adverse cardiac events such as heart attack, surgery or death compared to the group of patients that did not receive beta radiation
In the triple-blinded trial, neither patients nor doctors nor the reviewer of the results knew in advance which patients received radiation. Mohan Suntharalingam, M.D., of the University of Maryland wasn't surprised at the outcome based on the results of previous studies. However, "I was surprised that the positive effect was so significant," he says.
In a related study, The Gamma II trial enrolled 125 patients - composed of 96 men and 29 women - from 12 centers to determine the safety and effectiveness of using gamma radiation to treat lesions - or blocked areas - up to 45mm long.
Unlike the START trial, all patients enrolled in the Gamma II trial received radiation treatments. Those eligible were between the ages of 18 and 85, had in-stent restenosis of a major artery and were candidates for coronary intervention.
Angiography was performed on 86 percent of the patients at nine months with results showing a 52 percent decrease of in-stent restenosis.
Prabhakar Tripuraneni, M.D., of Scripps Clinic, LaJolla, CA, is encouraged by the results of the Gamma II trial and optimistic about what it means to patients dealing with the recurring problem of artery blockage of lesions up to 45mm.
"I think we have found a cure or at least a good solution for in-stent restenosis," he says.
Comparatively, both studies conclude that the use of radiation - either beta or gamma - is an effective tool in the prevention of restenosis. While their results may be similar, what is still to be determined is if one system is superior to the other considering such factors as: risk factors of patients enrolled into these studies, expense, time allowed for procedure, exposure of radiation to staff and the size and length of the area being treated.
The studies were presented October 24 at the American Society for Therapeutic Radiology and Oncology annual meeting in Boston, MA.
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