Improvements in Critical Dosimetric Endpoints Using the Contura Multilumen Balloon Breast Brachytherapy Catheter to Deliver Accelerated Partial Breast Irradiation: Preliminary Dosimetric Findings of a Phase IV Trial

Abstract

Dosimetric findings in patients treated with the Contura multilumen balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) on a multi-institutional Phase IV registry trial are presented. Computed tomography-based three-dimensional planning with dose optimization was performed. For the trial, new ideal dosimetric goals included (1) ≥95% of the prescribed dose (PD) covering ≥90% of the target volume, (2) a maximum skin dose ≤125% of the PD, (3) maximum rib dose ≤145% of the PD, and (4) the V150 ≤50 cc and V200 ≤10 cc. The ability to concurrently achieve these dosimetric goals using the Contura MLB was analyzed. 144 cases were available for review. Using the MLB, all dosimetric criteria were met in 76% of cases. Evaluating dosimetric criteria individually, 92% and 89% of cases met skin and rib dose criteria, respectively. In 93% of cases, ideal target volume coverage goals were met, and in 99%, dose homogeneity criteria (V150 and V200) were satisfied. When skin thickness was ≥5 mm to <7 mm, the median skin dose was limited to 120.1% of the PD, and when skin thickness was <5 mm, the median skin dose was 124.2%. When rib distance was <5 mm, median rib dose was reduced to 136.5% of the PD. When skin thickness was <7 mm and distance to rib was <5 mm, median skin and rib doses were jointly limited to 120.6% and 142.1% of the PD, respectively. The Contura MLB catheter provided the means of achieving the imposed higher standard of dosimetric goals in the majority of clinical scenarios encountered.