Clinical and angiographic outcomes after use of 90Strontium/90Yttrium beta radiation for the treatment of in-stent restenosis: results from the Stents and Radiation Therapy 40 (START 40) registry

Purpose: To evaluate the safety and efficacy of a 40-mm 90Strontium/90Yttrium source train in the management of in-stent restenosis within native coronary arteries. Methods and Materials: This multicenter, prospective registry was designed to compare the results of patients with in-stent restenosis treated with a 40-mm source train to the placebo arm of the previously reported randomized Stents and Radiation Trial (START). All patients entered in the registry were treated with repeat balloon angioplasty followed by intravascular brachytherapy. Radiation dose was prescribed based on vessel size. 18 Gy was delivered at 2 mm for vessel diameters between 2.75 and 3.35 mm, and 23 Gy was used for vessels between 3.36 and 4.0 mm. The efficacy endpoints for the START 40 registry included a reduction in the target lesion revascularization (TLR) rate, target vessel revascularization rates, and target vessel failure (TVF) at 8 months. Secondary angiographic efficacy endpoints were binary restenosis at 8 months, in-stent minimum luminal diameter (MLD), and late loss. The safety endpoints included major adverse cardiac events as well as late aneurysm formation. The registry was designed to allow a statistically valid comparison of these results to the placebo group of the START 30 trial. Quantitative angiographic analysis was performed on the 8-month follow-up examination. Rates of restenosis were evaluated for various segments of the treated vessel. A separate analysis was performed to evaluate the relationship between vessel injury length and the radiated segment. Results: A total of 207 patients were entered into the START 40 registry. The postprocedure angiographic results, including the postprocedure MLD and percent diameter stenosis, were similar between the START 40 patients and the placebo group from the START trial in the stented segment of the treated vessel. Eight-month angiographic follow-up was available on 150 patients from the registry. The TLR rate was significantly reduced when compared to the placebo group (11% vs. 22.4% respectively, p=0.008). A similar reduction was seen in terms of target vessel revascularization (15.9% vs. 24.1%, p=0.03). The 8-month MLD was found to be significantly larger in the START 40 patients (1.85 mm vs. 1.47 mm, p<0.0001). The difference seen in the clinical endpoint of TVF (19.3% vs. 25.9%) did not reach statistical significance (p=0.1). Analysis of the procedural angiograms revealed mismatch between the length of vessel injured and the location of the 90% isodose in 46% of the treated cases. Angiographic analysis revealed that geographic miss was associated with a higher rate of binary restenosis (32% vs. 18% p=0.04) in the analysis segment. Conclusions: This multicenter registry demonstrates the safety and efficacy of a 40-mm 90Strontium/90Yttrium source train in the management of patients with in-stent restenosis. Restenosis rates were lowered with the use of this longer source train when compared to the placebo arm of the START trial for lesions with a maximum vessel injury length of 20 mm. Angiographic analysis identified the importance of the accurate delineation of injury length and correct source positioning. These results support the continued use of beta radiation for the treatment of this disease process