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INTRODUCTION Oncoplastic breast surgery (OBS) has been implemented with increasing frequency in the treatment of breast cancer. The aim of this study was to compare the oncologic outcome after OBS to the outcome after conventional breast-conserving surgery (BCS) in patients with invasive breast cancer. PATIENTS AND METHODS In all, 197 patients treated with OBS were compared to 1399 patients treated with conventional BCS from 2008 to 2013. We evaluated nonradical primary tumor excision, time to initiation of adjuvant therapy, disease-free survival (risk of recurrent disease), and survival (cause specific and overall). Identification of patients and follow-up were made using the Danish Breast Cancer Cooperative Group registry and the Danish Cause of Death registry. Multivariate logistic regression and the Cox proportional hazard analysis were used to obtain odds ratios and hazard ratios with 95% confidence intervals (CI). RESULTS There was a lower risk for nonradical primary tumor excision for patients undergoing OBS versus conventional BCS (adjusted odds ratio:95% CI, 0.50:0.29-0.84). No significant differences were found with regard to a delay in initiation of adjuvant chemotherapy (adjusted hazard ratio:95% CI, 1.14:0.89-1.45) or radiotherapy (0.91:0.71-1.16), disease-free survival (1.23:0.61-2.47), breast cancer as cause of death (1.46:0.52-4.09), breast cancer as underlying or multiple cause of death (0.90:0.34-2.37), or overall survival (0.90:0.51-1.60). CONCLUSION We found no significant differences in oncologic outcome comparing OBS to conventional BCS. However, a lower risk of nonradical primary tumor excision was found for patients treated with OBS. These results indicate that OBS is a safe procedure.