Background: The effects of beta-radiation with a (188)rhenium ((188)Re)-filled balloon catheter system on angiographically normal reference segments have not been well defined.
Methods: In the Seoul National University Post-Angioplasty Rhenium irradiation (SPARE) trial, patients with de novo or restenotic lesions were first treated with a conventional catheter-based technique and then randomized to either a radiation group or a control group. Irradiation was performed using a (188)Re-filled conventional balloon catheter system. Among 97 radiation group enrolled in this study from April 1998 through May 2001, 20 patients with de novo lesions who received brachytherapy with a balloon at least 10 mm longer than the length of an implanted stent, were selected and their post-intervention and follow-up intravascular ultrasound (IVUS) images were analyzed. Each reference segment was divided into two segments; full dose-irradiation with injury segment (irradiated segment; from the stent edge to the radiopaque balloon markers), and low dose-irradiation without injury segment (edge segment; 5-mm long segment proximal or distal to the location of radiopaque markers). In control group, serial IVUS analysis was available only in 10 patients, and IVUS parameters of the non-stented adjacent segments in these patients were compared to those of irradiated segments in radiation group patients.
Results: Forty irradiated and 38 edge segments of the 20 radiation group patients were analyzed. In proximal irradiated segments, no significant changes were found in external elastic membrane (EEM), lumen or in the plaque plus media (P&M) areas. In distal irradiated segments, significant increases in the EEM (12.5+/-4.5 to 14.0+/-5.0 mm(2), P<0.01) and P&M areas (5.5+/-2.0 to 6.6+/-2.3 mm(2), P<0.01) were found to occur without a change in lumen area. In proximal edge segments, P&M areas were significantly increased (9.0+/-1.7 to 10.5+/-2.6 mm(2), P=0.03). No significant changes in EEM, lumen or P&M areas were observed in the distal edge segments. Comparisons between the irradiated segments (n=40) in the radiation group and the non-stented adjacent segments (n=19) in the control group showed a significant difference in the percentage change of EEM areas (18.5+/-33.2% in radiation group vs. -3.1+/-32.1% in control group, P=0.02).
Conclusions: beta-radiation with a (188)Re-filled conventional balloon catheter system appears to have no significant deleterious effect on angiographically normal reference segments over a 6 months follow up after brachytherapy.