Introduction: Traditional indications for mastectomy include multiple ipsilateral lesions and/or disease spanning ≥ 5 cm. Neoadjuvant chemotherapy increases breast conservation but does not improve survival. We hypothesized that oncoplastic breast-conserving surgery (OPS) may allow for breast conservation while providing full staging and tumor profiling information to guide systemic therapy decisions, thereby permitting more judicious chemotherapy use. Methods: This was an observational cohort of patients with invasive breast cancer with multiple lesions and/or disease spanning ≥ 5 cm who underwent OPS from 2012 to 2018. Clinicopathologic features, mastectomy rate, chemotherapy use, and recurrence were evaluated. Results: Overall, 100 patients were identified. Average disease span was 62.8 ± 20.1 mm, with an average of 2.9 lesions (range 1–13). ‘No ink on tumor’ was achieved at the index operation in 80 patients; 13 patients underwent completion mastectomy to achieve adequate margins. Eighty-one patients completed radiation therapy. Breast conservation was possible in 50/58 (86%) patients who did not receive chemotherapy. Forty-two patients received chemotherapy (8 neoadjuvant, 34 adjuvant), of whom 37 (88%) achieved breast conservation. Twenty-six patients with high-risk features received adjuvant chemotherapy. Oncotype DX testing demonstrated the need for chemotherapy in an additional eight patients. After a median follow-up of 40 months, four patients had a local recurrence, including two who declined radiation therapy. Conclusions: OPS can facilitate breast conservation in most patients with traditional indications for mastectomy. Additionally, OPS may reduce unnecessary chemotherapy, especially in patients who qualify for Oncotype DX testing. Further study evaluating long-term oncologic and cosmetic outcomes is warranted.
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