Abstract P2-12-16: The use of oncoplastic surgical techniques to increase successful breast conservation in invasive lobular carcinoma of the breast

Background: Invasive lobular carcinoma (ILC) of the breast differs from invasive ductal carcinoma in its non-cohesive growth pattern. These diffuse tumors pose challenges for accurate size assessment as well as surgical resection. Patients with ILC have higher rates of positive margins and lower rates of successful breast conservation surgery. Oncoplastic surgical techniques such as oncoplastic reduction mammoplasty and lumpectomy with oncoplastic closure can allow for removal of larger areas of breast tissue than lumpectomy alone. Whether or not these techniques improve the success of breast conservation in patients with ILC is unknown. Methods: We queried a prospectively maintained surgical database and identified 384 women treated for ILC at UCSF between 1992 and April 2017. We reviewed pathology and operative reports, and clinical outcomes data, and identified 199 women who had an initial attempt at breast conservation. Data were analyzed in Stata 14.2. Results: Average age was 61 years (range 39-84), and 69% of patients underwent lumpectomy, 16% had lumpectomy with oncoplastic closure, and 15% had oncoplastic reduction mammoplasty. The majority of tumors were hormone receptor positive, Her2 negative, grade 2, T1 or T2, and 28% were node positive. A total of 156 women (78%) had successful breast conservation; of these, 34% had one re-excision, and 1 patient had two re-excisions. Positive margins were seen in 40% of patients overall, and were significantly lower in the lumpectomy with oncoplastic closure group and those who had shave margins taken. Among the patients who underwent lumpectomy only, obtaining shave margins was significantly associated with final negative margins (71% versus 53%, p = 0.033). Patients with oncoplastic reduction mammoplasty had significantly larger average tumor size (4.1 cm), and significantly more tissue removed (167 cm 3 ). Conclusions: Tailoring the surgical treatment to tumor size can increase the rate of successful breast conservation surgery for these diffuse, often non-palpable lobular cancers. For the women with the largest tumors, oncoplastic reduction mammoplasty was often recommended. This group likely represents women who were borderline candidates for breast conservation; despite this, oncoplastic reduction mammoplasty allowed 77% to ultimately have successful breast conservation. For the women with smaller tumors, removing additional tissue with shave margins and using oncoplastic techniques for closure when necessary clearly reduced positive margin rates. Surgeons should routinely obtain shave margins when performing partial mastectomy for women with ILC. Citation Format: Wong JM, Piper ML, Ewing C, Alvarado M, Esserman LJ, Sbitany H, Foster RD, Mukhtar RA. The use of oncoplastic surgical techniques to increase successful breast conservation in invasive lobular carcinoma of the breast [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-12-16.