Abstract P1-11-09: The impact of a change in margin width on rates of re-excision following breast conserving surgery

Abstract

Abstract Background: Surgical margin status is a predictor of ipsilateral breast tumor recurrence but the definition of an adequate surgical margin following breast conserving surgery (BCS) remains controversial despite published recommendations for acceptance of 'no tumor at ink'. BCS can be compromised by the need for a re-excision procedure which incurs inconvenience to patients and additional healthcare costs. We have previously shown that reducing the margin mandate from 5mm to 2mm does not influence rates of re-excision and the impact of adopting a more stringent margin policy of 'no tumor at ink' is now reported. Methods:A retrospective analysis examined rates of re-excision amongst patients undergoing BCS for both invasive carcinoma with or without admixed ductal carcinoma in situ (DCIS) or pure DCIS over two sequential 12 month time periods either prior to (GROUP 1; n=225) or immediately following (GROUP 2; n=238) a change in minimum margin policy from 2mm to 'no tumor at ink' when the latter was deemed an adequate definition of a negative margin. A total of 611 patients underwent non-reconstructive breast surgery for symptomatic and screen-detected cancers during these time periods among whom 463 received BCS. Wire-localization was undertaken in 51% (114/225) and 42% (101/238) of patients in groups 1 and 2 respectively. Data was extracted from electronic patient records of histopathology reports and clinic letters with further information available from documentation of MDT discussions. Statistical analysis used Fisher-Exact test. Results: Rates of re-excision were significantly lower for group 2 (32/238=13%) compared with group 1 48/225=21%). Re-excision encompassed cavity re-excision alone, cavity re-excision followed by mastectomy and completion mastectomy. Residual disease in re-excision specimens was significantly higher for group 2 (40.6%) compared with group 1 (16.6%) [p=0.02] with more than one-third of cases of residual disease in group 2 being exclusively DCIS. Three patients in each group required 2 additional operations to achieve negative margins. For groups 1 and 2, three-quarters or more cases (87% and 77% respectively) had only 1 or two margins positive and 2 cases in group 2 were re-excised for reasons other than a positive margin (e.g. tumor type). For group 1, re-excision cases were prompted by margin categories of 0mm (n=22), <1mm (n=18) and ≥1mm; <2mm (n=8) whilst for group 2 all re-excisions were prompted by tumor at ink (0mm). A hypothetical minimum margin of 1mm would have reduced the re-excision rate for group 1 to 40/225 or 17.7%. Conclusion: Re-excision was usually prompted by margins of <2mm when a 5mm margin policy prevailed. A more relaxed margin mandate of 'no tumor at ink' has led to halving of re-excision rates from 21% to 13% as opposed to 17.7% for a minimum margin of 1mm. This reduction in rates of re-excision is accompanied by an increase in the proportion of cases with residual disease in re-operation specimens. Longer-term follow up is essential to monitor in-breast local recurrence. Citation Format: Jiwa NE, Ayyar S, Provenzano E, Benson JR. The impact of a change in margin width on rates of re-excision following breast conserving surgery [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-11-09.