Abstract RF1-01: Postoperative Complication Rates of Minimally Invasive Mastectomy Compared to Conventional Mastectomy: A Prospective Multicenter Cohort Study (MARRES)

Abstract Background: Minimally invasive breast surgery (MIS), including robotic and endoscopic mastectomy, has emerged as an alternative to conventional mastectomy (CM). However, robust prospective multicenter data comparing postoperative complications between MIS and CM have been lacking. Methods: The MARRES study (NCT004585074) is a multicenter, prospective cohort was conducted at 18 institutions in South Korea. Women with breast cancer or BRCA1/2 mutation carriers who underwent total, skin-sparing, or nipple-sparing mastectomy followed by immediate breast reconstruction were enrolled. The primary endpoint is the rate of postoperative complications of Clavien-Dindo grade ≥3 between the MIS and CM groups. A prespecified non-inferiority analysis with 1:1 matching was conducted according to the protocol. Results: A total of 1,914 women (2,140 cases) were enrolled. After applying eligibility criteria, 1,875 women were included in the analysis: 584 underwent MIS and 1,291 underwent CM. A total of 2,095 cases were analyzed, including 678 MIS cases (52 endoscopic and 626 robotic) and 1,417 CM cases. Among them, 615 cases (90.7%) in the MIS group and 1,358 cases (95.8%) in the CM group were performed for breast cancer, while the remaining cases involved benign disease or risk-reducing mastectomy in BRCA1/2 mutation carriers. Meanwhile, out of 1,875 women analyzed, 253 women (13.5%) underwent bilateral mastectomy, of which 116 women (45.8%) were diagnosed with bilateral breast cancer. Among women with unilateral breast cancer (N=1,616), those undergoing MIS were younger (median age, 46.0 vs. 47.0 years; p=0.0003) and more frequently aged