Abstract PS2-06-09: Vacuum-assisted biopsy in the era of low-risk ductal carcinoma in situ active monitoring: real world data and implications

Abstract Abstract Background: The short-term oncological safe of active monitoring for ductal carcinoma in situ (DCIS) with low risk (LR-DCIS) of progression to invasive cancers (IC) has been demonstrated. This study evaluates vacuum assisted biopsy (VAB) as diagnostic test for LR-DCIS active monitoring (AM) in real-world clinical practice. Methods: Database analysis of 116 cancers both invasive breast cancers (IC) and ductal carcinoma in situ (DCIS) diagnosed by VAB submitted to standard surgical treatment with complete histological data from VAB and surgery from 04/13/2017 to 11/28/2020. The VAB results matched the surgical pathology, considered the gold standard, and AM criteria. The pathological diagnoses were grouped into malignancies requiring guideline surgical treatment DCIS with high risk (HR-DCIS) of progression to IC or IC versus those eligible to alternative active monitoring (LR-DCIS). HR-DCIS/IC were considered positive while LR-DCIS negative results. VAB sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were obtained. Results: Mean age 55.6 ± 12.27; mean IC size 7.14 ± 5.17mm and 12.6 ± 11.63mm for DCIS. Out of 116 malignancies diagnosed by VAB, 15 (12.9%) resulted LR-DCIS in the biopsy, 10 (8.6%) confirmed LR-DCIS in surgery, and 5 (4.3%) upgraded to HR-DCIS/IC in surgery. VAB showed 95.28% sensitivity, 100% specificity, PPV was 100%, and NPV 66.67%. VAB LR-DCIS AM was 6% (7/116) and underdiagnoses 1.7% (2 pT1a-bN0 hormone receptor positive). Conclusion: VAB LR-DCIS AM would lead to a moderate (6%) overall reduction of short-term breast cancer surgical overtreatment counterbalanced by few cases of underdiagnosed invasive cancers potentially treatable by adjuvant hormone therapy. Trial registration: retrospectively registered on 10/06/20219 in the Ethics Committee of Santa Casa of Belo Horizonte under the number 25761019.8.0000.5138 Citation Format: H. L. Couto, C. N. Valadares, A. N. Soares, B. T. Silva, B. F. Ricardo, P. H. Toppa, B. A. Coelho, V. Resende, E. C. Pessoa, F. M. Reis, T. C. Oliveira, D. d. Pires, S. d. Ferreira, L. B. Oliveira, P. M. Soares, T. P. Moraes, A. C. Mendonça, R. G. Saliba, L. L. Dominguez, B. A. Pires, C. A. Padua, G. F. Cunha Júnior, N. Sharma, M. S. Castilho, J. S. Oliveira, A. C. Oliveira, D. R. Siqueira, A. Mattar, M. Antonini, P. Clark, H. S. Bartels, H. L. Amorim, G. d. Silva Junior, A. d. Amorim. Vacuum-assisted biopsy in the era of low-risk ductal carcinoma in situ active monitoring: real world data and implications abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-06-09.