The margins effect: Residual tumor after breast conserving surgery

Abstract

11045 Background: Resection of breast cancer with good surgical margins is one of the fundamental aspects of breast conserving surgery. Most studies have shown that women with positive margins after breast conserving surgery (BCS) fared worse compared to those with negative margins, regardless of chemotherapy or radiation therapy. Nowadays, when partial breast irradiation is gaining popularity, understanding the natural history of positive or close margins is particularly important. We studied the surgical process in a large cohort of Israeli women with breast cancer to estimate the frequency of tumor margin involvement in the primary and subsequent surgical procedure. Methods: The National Israeli Breast Cancer Detection Programs has been monitoring the detection process of all new cases of breast cancer in Israel since 1996. Full data on tumor histology and surgical procedures, including indication of margins in the pathology report were available for 16,925 malignant breast tumors. Margins were classified as positive margins (PM), close (= 2mm) (CM) or negative margins (greater then 2mm)(NM). Results: BCS was identified in 14,815 women with invasive cancer and 2,110 with pure ductal carcinoma in situ (DCIS). Only 7,751 (52.3%) of the 14,815 women with invasive cancer had NM, while 2,868 (19.4%) had CM and 4,196 (28.3%) had PM. Among those with PM, 2,276 (54.6%) had a re-operation within 6 months from the index surgery and 1,265 (55.6%) of them were found to be malignant; 58% of them were invasive cancers and 42% DCIS. Among the invasives on re-operation, 24.4% still had PM and another 12.1% had CM while among the DCIS 14.4% had PM and 17.6% had CM. Of the 717 women with DCIS and positive margins at first surgery, 67.9% had a second operation. Of them, 59.8% had malignancy, 8.8% of them invasive. Overall 10.6% of all invasive cancers and 3.7% of all DCIS had PM on relumpectomy within 6 month regardless of initial margin status. Conclusions: A relatively high proportion of all women undergoing BCS were found to have positive or close margins, even after re-operations. If a failure to reach clean margins is a reflection of an aggressive tumor phenotype, special attention should be given to these patients and treatment should be adjusted accordingly. No significant financial relationships to disclose.