Three-Dimensional Bioabsorbable Tissue Marker Placement is Associated with Decreased Tumor Bed Volume Among Patients Receiving Radiation Therapy for Breast Cancer

Purpose: BioZorb ^® (Focal Therapeutics, Aliso Viejo, CA) is an implantable 3-dimensional bioabsorbable marker used for tumor bed volume (TBV) identification during postoperative radiation therapy (RT) planning. We aimed to calculate and compare RT TBVs between two cohorts managed with and without the device. Methods and Materials: Data from patients with breast cancer who were treated at Rhode Island Hosptial, Providence RI between May 1, 2015 and April 30, 2016 were retrospectively reviewed and grouped based on 3-dimensional bioabsorbable marker placement. Pathology reports were used to calculate tumor excision volume (TEV) after breast conservation. Specifically, the three dimensions provided were multiplied to generate a cubic volume, defined as TEV. TBV was calculated using treatment volumes generated with Philips Pinnacle3 treatment planning software (Andover, MA). Linear regression analyses assessed the relationship between excised TEV and TBV. T tests compared the slopes of the best fit lines for plots of TEV versus TBV. Results: In this retrospective case-control study, 116 patients undergoing breast RT were identified; of whom 42 received a 3-dimensional bioabsorbable marker and 74 did not. The mean TEVs were 102.7 cm ³ with the device and 103.2 cm ³ without the device, and the mean TBVs for the same groups were 27.5 cm ³ and 40.1 cm ³ , respectively. The TBV standard errors for patients who did and did not receive 3-dimensional bioabsorbable markers were 23.739 and 38.685, respectively. The t tests found the slopes of the lines of best fit for these cohorts to be statistically significantly different (P =.001), with smaller TBVs achieved with 3-dimensional bioabsorbable marker placement. Conclusions: When comparing TBVs between patients contemporaneously treated with or without a 3-dimensional bioabsorbable marker, device placement was associated with statistically significantly smaller TBVs in the setting of similar TEVs.