Elderly patients have a favorable outcome after intracoronary radiation for in-stent Restenosis

Intracoronary radiation therapy (IRT) reduces recurrent in-stent restenosis (ISR) by inhibition of smooth muscle cell proliferation. The ability of these cells to replicate is limited with age due to changes in the telomeres. The purpose of this study was to assess the effect of age on outcomes following IRT for ISR. We evaluated 1,088 patients with 6-month clinical follow-up who were enrolled in radiation trials for ISR using gamma- and P-emitters. Patients were analyzed within and between IRT (n = 861) or placebo therapy (n = 227) in four age groups (< 55, 55-65, 66-75, > 75 years). Baseline characteristics were similar within each age group of IRT patients, except elderly patients (> 75 years) had a lower rate of diabetes (28% in patients > 75 years; P = 0.008) and a higher rate of previous CABG (59% in patients > 75 years; P < 0.001). The rate of target lesion revascularization (TLR) was reduced in the elderly. TLR at 6 months was 18% in patients < 55 years, 21% in 55-65 years, 12% in 66-75 years, and 10% in patients > 75 (P = 0.009). The MACE rate at 6 months was 21% in patients < 55 years, 29% in 55-65 years, 26% in 66-75 years, and 17% in patients > 75 (P = 0.03). No effect of age was seen in placebo patients. IRT-treated patients had reduced MACE compared to placebo in all age groups, driven by reduced target vessel revascularization. Age was an independent predictor of MACE at 6 months (OR = 0.8; Cl = 0.70-0.93; P = 0.004). Angiographic restenosis was not clearly associated with need for TLR in patients > 75 years. In elderly patients I(> 75 years) treated with IRT for ISR, the rate of TLR was significantly reduced compared to younger patients. However, this reduction in TLR was not associated with a reduction in angiographic restenosis, suggesting that TLR should not be used as a surrogate for angiographic evaluation.