Clinical implementation of a novel Double-Balloon single-entry breast brachytherapy applicator

The purpose of the study was to describe the clinical utilization of a novel Double-Balloon applicator for accelerated partial breast irradiation (APBI).

The Double-Balloon single-entry breast applicator contains a single central treatment catheter, as well as four peripheral catheters that can be differentially loaded to customize radiation dose coverage. An inner balloon is filled with up to 7-30 cm³ of saline to increase separation between the peripheral catheters, and an outer balloon is filled with up to 37-115 cm³ of saline to displace breast tissue from the peripheral catheters. Treatment planning objectives include coverage of the breast planning target volume to a minimum of V₉₀ > 90%, limiting dose heterogeneity such that V₂₀₀ < 10 cm³ and V₁₅₀ < 50 cm³, and limiting maximum dose to skin (<100% of prescription dose) and ribs (<145% of prescription dose).

High-dose-rate APBI was delivered to 11 women using this device (34 Gy in 10 twice daily fractions). The mean V₉₀ was 98.2% (range 94.2-99.4%). The mean skin D_max with the Double-Balloon applicator was 83.3% (range 75.6-99.5%). The mean breast V₂₀₀ was 5.8 cm³ (range 2.3-10.2 cm³), and the mean breast V₁₅₀ was 32.9 cm³ (range 25.0-41.7 cm³). Pretreatment quality assurance was performed using CT prior to each morning fraction and ultrasound prior to each afternoon fraction.

The Double-Balloon applicator can be easily introduced into a previously existing brachytherapy program. APBI plans created with this applicator achieve excellent planning target volume coverage, while limiting skin dose and maintaining breast V₂₀₀ < 10 cm³.