Utility Of A Three-Dimensional Bioabsorbable Tissue Marker In Delineating The Lumpectomy Cavity.

78 Background: Advanced methods of external beam radiotherapy are not widely used to deliver post-operative treatment for breast cancer due to difficulty in defining the target region surrounding the surgical cavity. Common targeting methods utilize surgical clips and/or seroma based tissue changes. However, these methods can result in over-estimation of treatment volumes resulting in undesirable radiation exposure to adjacent normal tissues. In addition, these techniques fall short of the required precision necessary to utilize newer methods of radiation delivery. In order to assess its ability to assist with identification of the surgical excision site, we evaluated a 3-dimensional tissue marker surgically placed during partial mastectomy.A total of 30 patients were implanted with a 3-D bioabsorbable tissue marker at the time of partial mastectomy. Post-operative CT simulation and treatment plans were generated and compared. The tissue marker was rated for its utility in defining the target area for treatment planning as well as day to day patient positioning between fractions. Most patients received standard whole breast irradiation with a boost to the tumor bed as treatment, however advanced techniques were used in selected cases.The marker was easy to use with standard surgical techniques. No complications were reported and it was consistently and easily visualized with clinical imaging allowing it to be readily incorporated into standard and advanced planning methods. The marker had appreciable benefits when designing optimal treatment plans, particularly when no seroma fluid remained. In these cases, the marker identified the surgical site that could not have been identified using traditional methods, and target volumes were decreased by >40% in most cases. In addition, the device assisted with image-based tracking of the lumpectomy cavity during respiratory motion (4-D CT) enabling use of IGRT.The Biozorb tissue marker provided a consistent method for identifying the lumpectomy site and was a useful tool for post-operative radiotherapy and clinical followup. In addition, it provided a novel method of marking the lumpectomy cavity when using oncoplastic techniques.