Vascular brachytherapy using a beta emitter source in diabetic patients with in-stent restenosis: angiographic and
Mohan Suntharalingam1, Warren K Laskey, Wiwun Tantibhedhyangkul
1Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore 21201, USA. nsunthar@umaryland.edu
Purpose:
The management of diabetic patients with restenosis after percutaneous coronary intervention remains a significant challenge. Diabetic patients remain at significant risk of restenosis despite stent implantation. This retrospective analysis was performed to determine the extent to which vascular brachytherapy improves late clinical and angiographic outcomes in diabetic patients compared to conventional therapy and compared to patients' nondiabetic counterparts.
Methods:
Pooled data from two studies (START [Stents and Radiation Trial] and START-40 trials) of patients (204 diabetic, 477 nondiabetic) receiving vascular brachytherapy (VBT) with a (90)Sr/(90)Y source after conventional percutaneous coronary intervention for in-stent restenosis comprise the study population. The radiation delivery system used in both studies was the Beta-Cath system. The prescribed dose at 2 mm from the centerline of the source axis was 18.4 Gy or 23 Gy, depending on vessel diameter. The reference vessel diameter, minimal lumen diameter, and percent diameter stenosis were measured before the intervention, at the conclusion of the procedure, and at the 8-month follow-up examination. The Breslow-Day test was used to formally assess the similarity of treatment effect between diabetic and nondiabetic patients.
Results:
Target lesion and target vessel revascularization rates and angiographic restenosis rates in diabetic and nondiabetic patients treated with beta radiation or placebo were analyzed. Diabetic patients were more likely to have longer and more complex coronary lesions. In-hospital outcomes in diabetic and nondiabetic patients were similar, irrespective of treatment status. At 8 months, patients treated with beta radiation exhibited less target lesion revascularization (diabetic: 10.9% vs. 22.7%, p = 0.02; nondiabetic: 12.8% vs. 22.3%, p = 0.007) and less target vessel revascularization (diabetic: 14.7% vs. 25.3%, p = 0.06; nondiabetic: 16.6% vs. 23.6%, p = 0.06) compared to placebo. In-stent binary angiographic restenosis was lower in irradiated patients (diabetic: 19.4% vs. 37.3% for placebo, p = 0.01; nondiabetic: 12.9% vs. 43% for placebo, p < 0.001). However, restenosis beyond the stent site reduced the impact of VBT, regardless of diabetic status. The magnitude of the treatment effect for target lesion and target vessel revascularization rates was similar between diabetic and nondiabetic patients.
Conclusions:
Previously published institutional experiences have suggested that diabetic patients benefit from the use of VBT in the management of in-stent restenosis. This analysis now provides direct evidence to support the role of beta radiation VBT in this patient population. Diabetic patients undergoing this therapy are just as likely to benefit from it as their nondiabetic counterparts.