Impact of Using Intra-Operative Ultrasound Guided Breast- Conserving Surgery on Positive Margin and Re-Excision Rates in Breast Cancer Cases with Current SSO/ASTRO Guidelines.

Purpose: To review the impact of using intra-operative ultrasound guided breast conserving surgery with frozen sections on nal pathological margin outcome with the current guidelines set forth by the Society of Surgical Oncology (SSO) and the American Society of Surgical Oncology (ASTRO).

Materials And Methods: A retrospective review including all cases of intra-operative ultrasound guided breast conserving surgery was performed at the National Cancer Institute Thailand between 2013 and 2016. Patient demographics, tumor variables, intraoperative frozen section and nal pathological margin outcomes were collected. Factors for positive or close margins were analyzed.

Results: A total of 86 patients aged between 27 and 75 years with intra- operative ultrasound guided breast conserving surgery were included. Three cases (3.5%) of positive margin were detected by intra-operative frozen section and 4 cases (4.7%) by final pathology reports. There were 18 cases (20.9%) with a close margin (<1 mm). Factors affecting this result comprised multi-foci, presence of invasive ductal carcinoma (IDC) combined with ductal carcinoma in situ (DCIS) and invasive lobular carcinoma (ILC).

Conclusions: With the current SSO/ASTRO for adequate margin guidelines, using intra-operative ultrasound to locate the boundary for resection with breast conserving surgery provided a high success rate in obtaining final pathology free margin outcomes and minimizing re-operation risks especially when combined with intra-operative frozen section assessment. The chance of finding positive or close margins appears higher in cases of IDC combined with DCIS, ILC and with multi-foci cancers.