Simple SummaryScreening programs are increasingly leading to a decrease in the diagnosis of locally advanced breast cancer, especially cT4 breast cancer. Currently, therapy is based on a definite scheme consisting of neoadjuvant chemotherapy (NA), surgical therapy, radiation therapy, and possible adjuvant therapy, regardless of the biological histotype. Surgical therapy for this type of treatment has been based on demolitive surgery aimed at achieving complete removal of the neoplasm without consideration of aesthetic outcomes. Recently, conservative surgery has progressively increased in importance in patients with cT4, especially in the presence of a major neoplastic response to chemotherapy. To date, however, few studies have compared the two types of surgery in terms of oncological outcomes (loco-regional disease-free survival, distant disease-free survival, and overall survival). Our aim was to compare these two types of surgery to assess the safety of conservative versus radical therapy.AbstractBackground: The diffusion of screening programs has resulted in a decrease of cT4 breast cancer diagnosis. The standard care for cT4 was neoadjuvant chemotherapy (NA), surgery, and locoregional or adjuvant systemic therapies. NA allows two outcomes: 1. improve survival rates, and 2. de-escalation of surgery. This de-escalation has allowed the introduction of conservative breast surgery (CBS). We evaluate the possibility of submitting cT4 patients to CBS instead of radical breast surgery (RBS) by assessing the risk of locoregional disease-free survival, (LR-DFS) distant disease-free survival (DDFS), and overall survival (OS). Methods: This monocentric, retrospective study evaluated cT4 patients submitted to NA and surgery between January 2014 and July 2021. The study population included patients undergoing CBS or RBS without immediate reconstruction. Survival curves were obtained using the Kaplan-Meyer method and compared using a Log Rank test. Results: At a follow-up of 43.7 months, LR-DFS was 70% and 75.9%, respectively, in CBS and RBS (p= 0.420). DDFS was 67.8% and 29.7%, respectively, (p= 0.122). OS was 69.8% and 59.8%, respectively, (p= 0.311). Conclusions: In patients with major or complete response to NA, CBS can be considered a safe alternative to RBS in the treatment of cT4a-d stage. In patients with poor response to NA, RBS remained the best surgical choice.