Outcomes of Radiation Overlap and Margin Length in Intracoronary Brachytherapy for In-Stent Restenosis

Background: In-stent restenosis (ISR) is a common complication following coronary stent implantation. Intracoronary brachytherapy (ICBT) has re-emerged as an effective treatment modality. However, optimal procedural strategies, including the role of radiation source overlap and adequate margin length, remain unclear. Aims: To evaluate the impact of radiation source overlap and radiation margin adequacy on procedural and clinical outcomes in patients undergoing ICBT for ISR. Methods: We conducted a retrospective, single-center study of 222 patients treated with ICBT for ISR between June 2016 and December 2024. Patients were stratified using radiation source overlap (single vs. double dwell) and radiation margin length (< 10 vs. ≥ 10 mm). The primary endpoint was 1-year target lesion revascularization (TLR). Secondary endpoints included 1-year and 3-year all-cause mortality and 1-year major adverse cardiovascular events (MACE). Results: Among 222 patients (mean age 65.1 ± 0.7 years; 28.9% female), 42 (19.3%) received overlapping radiation, and 1616 (74.8%) had radiation margins ≥ 10 mm. TLR rates at 1 year were similar between overlap and non-overlap groups (HR = 1.26, 95% CI [0.68−2.31], p = 0.46). There were no significant differences in 1-year mortality (HR = 0.79; 95% CI [0.27–2.29]; p = 0.67) or 1-year MACE (HR = 1.17; 95% CI [0.66–2.10]; p = 0.59). Patients with margins ≥ 10 mm had similar rates of 1-year TLR compared to those with margins < 10 mm (HR = 0.61; 95% CI [0.16−2.30], p = 0.47). Both groups were associated with rates of 1-year mortality (HR = 0.73, 95% CI [0.33−1.60], p = 0.43) and 1-year MACE (HR = 0.98; 95% CI [0.63−1.53], p = 0.94). Conclusion: Radiation source overlap and short (< 10 mm) or extended (≥ 10 mm) treatment margins beyond the restenotic lesion do not compromise the safety or efficacy of ICBT. These findings support a more individualized, anatomy-guided approach to ICBT planning, which may enhance procedural feasibility without sacrificing long-term outcomes.