Breast conserving therapy after neoadjuvant chemotherapy; data from the Dutch Breast Cancer Audit

Introduction: NAC has led to an increase in breast conserving surgery (BCS) worldwide. This study aims to analyse trends in the use of neoadjuvant chemotherapy (NAC) and the impact on surgical outcomes. Methods: We reviewed all records of cT1-4N0-3M0 breast cancer patients diagnosed between July 2011 and June 2016 who have been registered in the Dutch National Breast Cancer Audit (NBCA) (N = 57.177). The surgical outcomes of ‘BCS after NAC′ were compared with ‘primary BCS′ using a multivariable logistic regression model. Results: Between 2011 and 2016, the use of NAC increased from 9% to 18% and ‘BCS after NAC’ (N = 4170) increased from 43% to 57%. We observed an involved invasive margin rate (IMR) of 6,7% and a re-excision rate of 6,6%. As compared to ‘primary BCS′ the IMR of ‘BCS after NAC′ is higher for cT1 (12,3% versus 8,3%; p < 0.005), equal for cT2 (14% versus 14%; p = 0.046) and lower for cT3 breast cancer (28,3% versus 31%; p < 0.005). Prognostic factors associated with IMR for both ‘primary BCS′ as for ‘BCS after NAC′ are: lobular invasive breast cancer and a hormone receptor positive receptor status (all p < 0,005). Conclusion: The use of NAC and the incidence of ‘BCS after NAC′ increased exponentially in time for all stages of invasive breast cancer in the Netherlands. This nationwide data confirms that ‘BCS after NAC′ compared to ‘primary BCS′ leads to equal surgical outcomes for cT2 and improved surgical outcomes for cT3 breast cancer. These promising results encourage current developments towards de-escalation of surgical treatment.