Luca Nicosia ^1,2* Luciano Mariano ² Antuono Latronico ² Anna Bozzini ² Federica Bellerba ² Aurora Gaeta ² Filippo Pesapane ² Giovanni Mazzarol ² Nicola Fusco ² Giovanni Corso ² Claudia Sangalli ² Cristian Giailan ² Matteo Lazzeroni ² Sara Raimondi ² Enrico Cassano ²

• ¹ University of Insubria, Varese, Lombardia, Italy
• ² European Institute of Oncology (IEO), Milan, Lombardy, Italy

Background: surgery is still the standard treatment for breast lesions such as in situ Ductal Carcinoma (DCIS); however, its survival benefit is minimal, particularly for low-grade DCIS.Surgical complications and related depression status can adversely affect patients' quality of life.Approximately 25% of Breast Cancer (BC) cases are in situ forms, with DCIS making up 90% of these. Low and intermediate-grade DCIS often grow slowly and do not always progress clinically significant diseases. Identifying non-invasive lesions could help prevent overtreatment. In this context, new diagnostic tools like Vacuum-Assisted Excision (VAE) could enhance the management of these conditions.Methods: the prospective VACIS study explores the role of VAE in ensuring the absence of pathology at subsequent surgery and reducing the diagnostic underestimation of breast biopsies for microcalcifications. Patients with suspicious breast microcalcifications up to 15 mm, who are candidates for stereotactic biopsy, will be enrolled and randomised into two groups. The control group will complete the biopsy with typical sampling, aiming to collect some microcalcifications from the target, while the experimental group will focus on the complete removal of the biopsy target (confirmed by mammography on the biopsy table), followed by a second sequence of cleaning samples. Radiograms will confirm lesion removal. Pathologic outcomes at surgery will be compared between the groups, and the percentage of underestimation will be assessed. The sample size is calculated to be 70 patients per group, using statistical tests and multivariate logistic models to detect a significant difference in the absence of pathology. Data collected will include patient age, lesion characteristics, and details of the biopsy, pathology and surgery.Discussion: current surgical treatments for low-and sometimes intermediate-grade DCIS offer limited survival benefits and may hurt patients' quality of life due to surgery-related complications and associated depression. These lesions often grow slowly and might not become clinically significant, suggesting a need to avoid overtreatment. Improved diagnostics procedures, such as VAE, could help distinguish non-invasive from potentially invasive lesions, reduce biopsy underestimation, enable personalised management and optimise treatment strategies. This study hypothesises that VAE could be a viable alternative to surgery, capable of removing pathology during the biopsy procedure.