Incidence and predictors of late recurrence after β-radiation therapy with a ¹⁸⁸Re-MAG₃-filled balloon for diffuse in-stent restenosis

Background: The long-term fate of patent irradiated segments at 6 months after β-radiation therapy has not been sufficiently evaluated. Methods: Two-year follow-up angiography was performed in 52 patients with patent irradiated segments at 6 months after β-radiation with a rhenium 188-mercaptoacetyltriglycine-filled balloon for diffuse in-stent restenosis. We evaluated late recurrence (LR) and its predictors after β-radiation. Results: Late recurrence at 2 years after radiation was observed in 10 (19.2%) of 52 patients. The minimal lumen diameter (MLD) progressively decreased, from 2.67 ± 0.44 mm at postprocedure to 2.42 ± 0.53 mm at 6 months to 2.09 ± 0.75 mm at 2 years (P = .001). In the 42 patients without LR, the MLD decreased from postprocedure (2.74 ± 0.43 mm) to 6 months (2.44 ± 0.54 mm; P = .006), but did not change between 6 months and 2 years (2.35 ± 0.49 mm, P = .13). In the LR group, the MLD was unchanged from postprocedure (2.33 ± 0.29 mm) to 6 months (2.30 ± 0.43 mm; P = .81), but decreased significantly between 6 months and 2 years (1.02 ± 0.75 mm, P = .001). Multivariate analysis identified postprocedural MLD as an independent predictor of LR (odds ratio 0.025, 95% CI 0.007-0.94, P = .04). Late target lesion revascularization was performed in 6 patients (11.5%) between 6 months and 2 years after radiation. Conclusion: Although LR after radiation was observed in some patients, irradiated segments remained stable for up to 2 years in most patients. Smaller postprocedural MLD, followed by delayed late loss between 6 months and 2 years, was associated with LR.