RESUMO
BACKGROUND: Breast-conserving surgery (BCS) still remains a blind surgery despite all available tumor localization methods. Intraoperative ultrasound (IOUS) allows real-time visualization during all resection phases. METHODS: This was a prospective observational cohort study conducted at the Veneto Institute of Oncology between January 2021 and June 2022. Patients with ductal carcinoma in situ, T1-2 invasive cancer, or post-neoadjuvant tumors, suitable for BCS, were recruited. All breast cancer lesion types were included, i.e. solid palpable, solid non-palpable, non-solid non-palpable, and post-neoadjuvant treatment residual lesions. Eligible participants were randomly assigned to either IOUS or traditional surgery (TS) in a 1:1 ratio. The main outcomes were surgical margin involvement, reoperation rate, closest margin width, main specimen and cavity shaving margin volumes, excess healthy tissue removal, and calculated resection ratio (CRR). RESULTS: Overall, 160 patients were enrolled: 80 patients were allocated to the TS group and 80 to the IOUS group. IOUS significantly reduced specimen volumes (16.8 cm3 [10.5-28.9] vs. 24.3 cm3 [15.0-41.3]; p = 0.015), with wider closest resection margin width (2.0 mm [1.0-4.0] vs. 1.0 mm [0.5-2.0] after TS; p < 0.001). Tumor volume to specimen volume ratio was significantly higher after IOUS (4.7% [2.5-9.1] vs. 2.9% [0.8-5.2]; p < 0.001). IOUS yielded significantly better CRR (84.5% [46-120.8] vs. 114% [81.8-193.2] after TS; p < 0.001), lower involved margin rate (2.5 vs. 15%; p = 0.009) and reduced re-excision rate (2.5 vs. 12.5%; p = 0.032). CONCLUSIONS: IOUS allows real-time resection margin visualization and continuous control during BCS. It showed clear superiority over TS in both oncological and surgical outcomes for all breast cancer lesion types. These results disfavor the paradigm of blind breast surgery.