Edge stenosis and geographical miss following intracoronary gamma radiation therapy for in-stent restenosis

OBJECTIVES We sought to determine the relationship between geographical miss (GM) and edge restenosis (ERS) following intracoronary radiation therapy. BACKGROUND Edge restenosis may be a limitation of intracoronary irradiation to prevent in-stent restenosis (ISR). Inadequate radiation source coverage of the injured segment (GM) has been proposed as a cause of ERS. We studied the relationship between GM and ERS following 192Ir treatment of ISR. METHODS There were 100 patients with native vessel ISR in WRIST (Washington Radiation for In-Stent Restenosis Trial), in which patients with ISR were first treated with conventional techniques and then randomized to gamma irradiation (192Ir) or placebo. Geographical miss was defined as segments proximal or distal to the treated lesion that were subjected to injury during primary intervention but were not covered by the radiation source. RESULTS Geographical miss was documented in 56 of 164 edges (34%). Edge restenosis was noted at eight of 80 radiated edges and in four of 84 placebo edges. In the irradiated group, ERS was observed in 21% of edges with GM and in 4% of edges without GM (p = 0.035). In contrast, in the placebo group, ERS was observed in only 7% of edges with GM and in 4% of edges without GM (p = NS). The late edge lumen loss was higher in the irradiated group with GM as compared to placebo with GM (0.74 ± 0.57 vs. 0.41 ± 0.50 mm, P = 0.016). CONCLUSIONS Edge restenosis following gamma irradiation treatment of ISR is related to GM: a mismatch between the segment of artery injured during the primary catheter-based intervention and the length of the radiation source.