Non-Invasive 3D Breast Tumor Localization: A Viable Alternative to Invasive Tumor Marking

Simple Summary Tumor marking before neoadjuvant systemic therapy (NAST) is an essential part of early breast cancer treatment, aiming to enable adequate surgical excision of the tumor bed in cases with complete clinical regression. Standard surgical techniques for targeted excision generally rely on the invasive insertion of various markers (radiopaque clips, radioactive seeds, silver wire, etc.) into or around the tumor. These techniques are burdened by technical complexity, the risk of complications (hematoma, infection, marker migration, etc.), and limited precision in the insertion and later identification of markers. Herein, we present our original technique of non-invasive three-dimensional tumor localization before and repeatedly during NAST and the preliminary results of its application. Multiple repetitions (monitoring the occasionally eccentric pattern of tumor regression) without the risk of complications suggest a possible advantage over invasive marking techniques. Application in surgical centers lacking trained staff and equipment for invasive tumor marking may impact the quality improvement of post-NAST breast cancer surgery in those centers.Abstract Background: We present a detailed description and the preliminary results of our original technique for non-invasive three-dimensional tumor localization in the breast, which was created as an alternative to standard invasive tumor marking before neoadjuvant systemic therapy (NAST), aiming to enable adequate surgery after complete tumor regression. Methods: A detailed description of the technique is provided in the main text. The technique's feasibility and precision were assessed in a single-arm, prospective study based on the histological parameters of the adequacy and rationality of the excision of completely regressed tumor beds. Results: Out of 94 recruited patients, 15 (16%) were deemed unsuitable, mainly due to the tumors' inadequate ultrasound visibility. Among the 79 processed patients, 31 (39%) had complete clinical regression after NAST and were operated on using our technique. The histological parameters of surgical precision (signs of tumor regression: 24/31; microscopic cancer residues: 7/31) were verified in all excised specimens (100% precision). There were no positive margins in seven cases with microscopic residues, indicating our technique's capacity to enable oncologically safe post-NAST surgery. Conclusions: The proposed technique is feasible and satisfactorily accurate in determining the location of regressed tumors, thus representing an alternative to invasive tumor marking, especially in surgical centers lacking trained staff and equipment for invasive marking. The technique's limitations are mainly related to the inadequate ultrasound visibility of the tumor.