Several studies showed a survival benefit in patients with pathological complete response (pCR), except for luminal A-patients suggesting that the response to PST may have clinical implications such as a higher chance to offer breast conserving therapy and a less extensive treatment of the axilla, if after PST, tumor-positive (axillary) lymph nodes are converted into ypN0.Randomized trials have established that administration of loco-regional radiation therapy (RT) to appropriately selected women who receive postoperative chemotherapy after mastectomy reduces loco-regional recurrence and breast cancer mortality. Eligible studies were identified through a systematic search of the medical literature performed independently by two researchers using a validated search strategy. An analysis of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-18 and B-27 PST trials identified initial clinical stage and response to therapy as significant predictors for local-regional recurrence (LRR) patients receiving mastectomy, none of whom received loco-regional RT. Development of GRADE (Grades of Recommendation, Assessment, Development and Evaluation) Recommendation by the Italian Association of radiation therapy and Clinical Oncology (AIRO). 

To conclude, we can say that electronic searches were supplemented by manually searching the references of included studies and review articles. Studies were identified on a search process performed by two independent reviewers (VL, LM), and uncertainty regarding eligibility was resolved by consulting a third reviewer. 

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