Definition of Tumor Bed Boost in Oncoplastic Breast Surgery: An Understanding and Approach

Definition of the tumor bed (TB) is currently guided by intraoperatively placed metal clips. However, this traditional planning method may not be sufficient for tumor cavity defect refilled with modern oncoplastic breast surgery. We explored the impact of a close cooperation between surgeon and oncologist on the accuracy of TB contouring after partial breast reconstruction with chest wall perforator flaps (CWPF).

A retrospective review of patients who received radiotherapy after CWPF was performed. TB and boost volume were defined by the surgeon, considering clips and the typical radiologic appearance of the flap, and by a radiation oncologist, and results were compared with the surgical specimen volume (SPV). The boost volume was marked as 5 mm penumbral ring thickness of native breast tissue wall around the replaced flap (nonbreast tissue).

There were no significant differences between SPV and surgeon-defined TB values. Conversely, the radiation oncologist-defined values were significantly smaller than the actual SPV. If a ring-shaped TB boost was delivered, this would have allowed a potential reduction of irradiated tissue of 127.6%.

TB definition solely by surgical clips may be prone to inaccuracy in case of volume replacement oncoplastic breast surgery. Our approach of combining the clips with the redefinition of the flap on computed tomographic scan may provide more accurate TB definition. Although an ideal ring-shaped boost might be difficult to reproduce in practice, it introduces a new paradigm: a lower radiation dose inside TB is tolerable, if not desirable, at least in CWPF.