Validation of a protocol for pre-operative flap thickness assessment on dual-view digital mammography for the decision-making process in implant-based breast reconstruction

Background: Pre-operative breast imaging is a critical component of the decision-making process for both oncological and reconstructive surgeons. The thickness of the non-glandular breast tissue coverage (BTC), including the skin and the subcutaneous fat layer overlying the anterior lamella of the capsula mammae, varies according to the single patient’s breast anatomy. This layer correlates with an anatomical and properly performed mastectomy to optimize mastectomy flap thickness. The aim of this study is to validate a BTC assessment modality that uses digital mammography (DM) imaging in both the cranio-caudal (CC) and the medio-lateral oblique (MLO) views.

Methods: We designed a retrospective, multi-reader study on a dataset of 40 unilateral DM cases obtained in the two standard views (CC and MLO). The study set was extracted from all consecutive cases recorded from January 2022 to March 2022 in two Breast Imaging Academic Centers involved in the project (the Breast Unit of the University of Naples Federico II and the Breast Unit of the University of Turin). The robustness of the proposed pre-operative assessments has been determined by deriving the metrics associated with the inter- and intra-observer agreement (P values of the matched measurements, measurement error, repeatability, limits of agreement, correlation) for each testing site and for their possible aggregations.

Results: We found a highly satisfactory inter-observer agreement with good correlation among the four senior radiologists’ measurements in all positions and on breasts of different density. The intra-observer agreement was also good: no significant differences and good correlation for either one. The method performed well also when used by less expert radiologists, satisfying the requirements for accuracy and repeatability set by the senior team. The analysis of the measured thickness consistently indicated a larger measurement error for the non-dense breast data than for the dense ones.

Conclusions: The proposed approach seems to be well-standardized and reproducible, allowing good performance at different levels of experience. It is our hope that this methodological study will assist with preoperative surgical planning by providing a clinical validation tool to estimate mastectomy flap thickness and its impact on preoperative decision-making for optimizing surgical-reconstructive outcomes, both from the oncological and the aesthetic point of view.