Finding an Alternative for the Surgical Clips-based Delineation of Tumor Bed Boost Volume for Radiotherapy after Breast Conserving Surgery: A Prospective Comparative Study

Abstract

Background: Radiotherapy after breast conserving surgery includes irradiation of whole breast and regional lymphatic areas which is followed by a boost to the tumor bed. Several different techniques have been proposed for delineation of tumor bed for boost. The purpose of the study was to identify the best method for localizing the tumor bed. Methods: 21 patients with histologically proven stage I and II infiltating ductal carcinoma of breast who underwent breast conserving surgery were included in the study. We delineated the boost volumes using five different techniques viz., patients’ self-localization, surgeon’s localization, pre-op CT based, scar-based and surgical clips based. The surgical clips-based volume is taken as a standard volume and the other volumes were compared with it. The outcome measures studied were the mean overlap volumes, the mean volume of surgical clips based volume missed by the other PTVs, the mean volumes of breast tissue outside the clips based PTV that could have been irradiated by the other PTVs. Results: None of the PTV volumes had good concordance with the surgical clips-based volume (PTV1). The best volume overlap was with patient’s self-localization (PTV3) albeit only being 34%. The scar-based localization volume had the least overlap with PTV1 (23%). The patients’ self-localization volume (PTV3) had the highest amount of breast tissue included outside PTV1 (64cc) and preop CT based volume (PTV4) included the least (42cc). Conclusion: Delineation of boost volume using surgical clips augmented by the simulation CT should be the standard technique for boost bed irradiation.

Comparison of dosimetry with magnetic resonance and computed tomography imaging delineation of surgical bed volume in breast cancer irradiation

“… 18 Further investigations on how to identify the SB using MRI are still in progress. 19 , 20 MR-guided radiotherapy with MR-Linac can also be used; however, breast treatment may benefit from respiration-guided irradiation, which if not controlled could lead to dosimetric differences in the irradiation of the whole breast PTV. Therefore, although the MR-Linac technology may seem attractive, the entire treatment needs to be evaluated, and further investigations are necessary.…”