Inhibition of Restenosis With β-Emitting Radiotherapy

Background —Intracoronary γ- and β-radiation have reduced restenosis in animal models. In the clinical setting, the effectiveness of β-emitters has not been studied in a broad spectrum of patients, particularly those receiving stents. Methods and Results —A prospective, randomized, sham-controlled study of intracoronary radiotherapy with the β-emitting 32 P source wire, using a centering catheter and automated source delivery unit, was conducted. A total of 105 patients with de novo (70%) or restenotic (30%) lesions who were treated by stenting (61%) or balloon angioplasty (39%) received 0 (control), 16, 20, or 24 Gy to a depth of 1 mm in the artery wall. Angiography at 6 months showed a target site late loss index of 11±36% in radiotherapy patients versus 55±30% in controls ( P <0.0001). A low late loss index was seen in stented and balloon-treated patients and was similar across the 16, 20, and 24 Gy radiotherapy groups. Restenosis (≥50%) rates were significantly lower in radiotherapy patients at the target site (8% versus 39%; P =0.012) and at target site plus adjacent segments (22% versus 50%; P =0.018). Target lesion revascularization was needed in 5 radiotherapy patients (6%) and 6 controls (24%; P <0.05). Stenosis adjacent to the target site and late thrombotic events reduced the overall clinical benefit of radiotherapy. Conclusions —β-radiotherapy with a centered 32 P source is safe and highly effective in inhibiting restenosis at the target site after stent or balloon angioplasty. However, minimizing edge narrowing and late thrombotic events must be accomplished to maximize the clinical benefit of this modality.