Abstract P4-13-01: Oncoplastic breast conservations – The Scottish Audit: Surgical techniques, oncological outcomes, complication rates and variations in practice across the country based on the analysis of 589 patients

Introduction: current evidence for oncoplastic breast conservation (OBC) is based on single institutional series. We studied the outcomes of OBC practice in Scotland and compare individual breast units. Methods: a predefined database of patients treated with OBC was completed retrospectively in 11 breast units in Scotland. Patients were treated with OBC from 2005 onwards were included. For statistical calculations Chi-test, ANOVA and Pearson correlation analysis were used. Results: Altogether 589 patients were included. Median age was 56 years [21-86]. Patients were diagnosed between September 2005 and March 2017. Number of patients treated with OBC per unit ranged between 4 and 145. High volume units were doing a mean of 19.3 OBCs per year [17.3 – 26.5] vs. low volume units doing 11.1 OBCs per year [7 .7– 14.4] (p=0.012). 23 different oncoplastic surgical techniques were applied. Range of oncoplastic techniques used was associated with case-loads: high volume units used a wider range (8 – 14 different techniques) compared to low volume units (3 – 6) (p=0.004). Volume displacement was done in 515 patients (91.3%), volume replacement in 49 patients (8.7%). OBC was carried out as a joint operation between a breast and a plastic surgeon in 66.3% (389 patients). Immediate contralateral symmetrisation rate was significantly higher when the procedure was carried out as a joint operation (70.7% vs. not joint operations: 29.8%; p Incomplete excision rate was 10.4% (60 of 578). Incomplete excision was significantly higher after invasive lobular carcinoma (18.9%; 10 of 43; p=0.0292). After neoadjuvant chemotherapy incomplete excision rate was significantly lower (3%; 2 of 66 vs. no neoadjuvant chemotherapy: 11%; 35 of 319; p=0.031). Neodjuvant systemic treatment rate was 28.6% (142 of 496 patients). Of those 68 patients received neoadjuvant chemotherapy (13.7%) and 74 patients had neoadjuvant hormonal treatment (14.9%). Neoadjuvant systemic treatment rate varied amongst the units from 9.7% to 57.2% for patients with invasive carcinoma. 259 patients diagnosed with (non)invasive carcinoma had a median follow-up time of 5 years [35-124]. Of these 7 patients (2.7%) developed isolated local recurrence. 5-year local recurrence rate after DCIS was higher than after pure invasive ductal carcinoma (DCIS: 8.3%; 3 of 36 vs. ductal: 1.6%; 3 of 181; p=0.02567). 5-year disease-free survival of these patients was 91.7%, overall survival was 93.8%, and cancer-specific survival was 96.1%. 145 of 510 patients developed complications, which is 28.4% overall complication rate. 71 patients had major complications (13.9%) and 74 patients had minor complications (14.5%). Overall complication rate was significantly lower after neoadjuvant chemotherapy (15.9%; 11 of 69) compared to patients who did not receive neoadjuvant chemotherapy (27.9%; 127 of 455 patients) (p=0.035). Conclusion: this national audit demonstrated similar outcomes overall compared to relevant published data. Units should be urged to build stronger collaboration in order to reduce variability in OBC practices. None of the authors have conflict of interest to declare. Citation Format: Romics L, Macaskill J, Fernandez T, Morrow E, Simpson L, Pitsinis V, Barber M, Tovey S, Masannat Y, Young O, Mansell J, Stallard S, Doughty J, Dixon M. Oncoplastic breast conservations – The Scottish Audit: Surgical techniques, oncological outcomes, complication rates and variations in practice across the country based on the analysis of 589 patients [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 P4-13-01.