Background: Data on the benefits of preoperative prophylactic antibiotics for breast surgery are conflicting and there is no guideline for their use for wire-localized lumpectomy. The aims of this study were to determine whether a single dose of pre-operative antibiotic reduces surgical site infection (SSI) for wire-localized lumpectomy and to identify risk factors for SSI.

Methods: This was a prospective randomized trial carried out from April 2018 to June 2019 at the "Centre des Maladies du Sein du CHU de Québec - Université Laval", a tertiary center specialized in breast surgery. After informed consent, patients who underwent wire-localized lumpectomy were randomized to receive or not a pre-operative single dose of prophylactic antibiotic (cefazolin 2 g or clindamycin 900 mg in case of penicillin allergy). Data regarding demographics, comorbidities, perioperative details, and SSI were analyzed. SSI was considered if: 1) patient had positive wound cultures; or 2) required abscess drainage; or 3) received antibiotic treatment for breast symptoms (e.g., swelling, erythema, congestion) within 30 days after operation, in the absence of wound culture or in the presence of negative results. The patients and the investigator responsible for data collection were blind to grouping. All patients were called 30 days after surgery to be sure that they did not consult at another hospital for surgical wound infection.

Inclusion Criteria:

• >18 years of age
• female
• scheduled for a wire-localized lumpectomy

Exclusion Criteria:

• pregnant or breastfeeding women
• incapacity to give informed consent
• preoperative breast infection
• patients known to be colonized with MRSA
• immunocompromised patients
• preoperative antibiotic prophylaxis needed for any concomitant condition.