Angiographic restenosis following intravascular β-brachytherapy does not correlate with delivered dose: a study with dose volume histograms

Introduction

Vascular brachytherapy reduces recurrence after treatment of in-stent restenosis. However, there are still failures. The aims of the study were to investigate the relationship between two distinct dose prescriptions and the calculated dose delivered versus binary angiographic restenosis.

Methods and Materials

Fifty-five lesions in 47 patients underwent catheter-based β-brachytherapy with a ³²P source. Doses delivered were calculated using intravascular ultrasound (IVUS) measurements. Patients randomly received 20 Gy either at 1 mm beyond mean reference lumen or 1 mm beyond mean reference external elastic membrane. Using subsequent offline volumetric IVUS measurements, dose volume histograms (DVHs) for the adventitia were determined.

Results

There were 13 restenotic lesions including four total occlusions. All recurrences localized within stented segment. The frequency of restenosis was similar between dosimetry groups (20% vs. 28%; P=.5). DVH calculations were similar in restenotic versus restenosis-free lesions. However, postprocedural IVUS minimal lumen area was significantly smaller for lesions that recurred (5.03±1.19 mm² vs. 6.13±1.7 mm²; P=.042).

Conclusions

Calculated cumulative doses delivered to the tissues do not correlate with clinical outcome. However, an adequate lumen may be important to accommodate even a small amount of recurrent intimal hyperplasia to limit restenosis and need for target lesion revascularization.