Surgeon seniority and performance in breast-conserving surgery for non-palpable lesions: evidence from a multicenter study.

Breast-conserving surgery (BCS) for non-palpable lesions is technically demanding, often performed by surgical trainees under supervision. Despite extensive literature evaluating localization techniques, only few studies have directly examined the role of surgeon seniority in determining surgical performance in this specific setting. We conducted a retrospective multicenter analysis (LOCALIZATION01 study, NCT05942105) including 3,195 patients who underwent BCS for non-palpable breast lesions between 2016 and 2024 across 12 Breast Units. Four localization techniques were used: wire-guided (WGL), radioguided occult lesion localization (ROLL), magnetic seed localization (MSL), carbon localization (CL). Outcomes included margin status, calculated resection ratio (CRR), operative time, and complications, stratified by surgeon seniority (attending vs resident). Most procedures were performed by attending surgeons (89.3%, n = 2,855) compared to residents (10.7%, n = 340). Margin positivity rates didn't differ significantly across localization techniques (e.g., ROLL 3.7% vs 2.3%, p = 0.30; MSL 9.4% vs 4.4%, p = 0.11, WGL 2.7% vs 5.9 p = 0.16, CL 0% vs 9.6% p = 0.10). Residents achieved better CRR in ROLL procedures (2.0, IQR 3, [1-47] vs 2.8, IQR 5, [1-78], p = 0.006), but had longer operative times, particularly with SLNB (e.g., MSL 60 min, IQR 31, [37-98] vs 55 min, IQR 20, [18-180], p = 0.02). Complication rates were low and comparable between groups. In a supervised setting, surgeon seniority doesn't significantly impact margin status, complication rates, or overall oncologic safety in BCS for non-palpable breast lesions. Localization methods with high reproducibility, such as ROLL and MSL, may mitigate the influence of surgical inexperience. These findings support the safe involvement of trainees in BCS under adequate supervision.