• Surgical site infection rates in patients with BMI over 25: the risk ratio (RR) contrasting the rate in the prophylaxis group to the rate in the placebo group, and the 95% CIs for the RR. [ Time Frame: 1 month ] [ Designated as safety issue: Yes ]
  

• The risk ratio (RR) contrasting the surgical site infection rate in the group with BMI over 25 who received placebo to the rate in the group with normal BMI. [ Time Frame: 1 month ] [ Designated as safety issue: Yes ]
  
• Cost-effectiveness of receiving antibiotic prophylaxis in overweight patients. [ Time Frame: 1 month ] [ Designated as safety issue: No ]
  

CONTEXT Although breast surgery is regarded as clean surgery, the actual surgical infection rate is well above accepted range in various series. Retrospective studies showed BMI as one of the factors which may have caused increased SSI rate after breast cancer surgery. Yet, no prospective randomized study assessed the efficacy of chemoprophylaxis during breast surgery in overweight patients. OBJECTIVE To compare the SSI rate between three groups of early stage breast cancer patients in which two are assigned according to randomization. First, patients are grouped into two according to their BMI. All patients (Group I) with BMI equal to or below 25 do not receive any antibiotics as prophylaxis. Patients with a BMI above 25 are randomly assigned to receive a single dose prophylactic ampicillin /sulbactam combination before surgery or not to receive chemoprophylaxis. DESIGN, SETTING AND PATIENTS Patient recruitment is still continuing after the study started in October 2003 in order to reach a sample size of 360 patients with BMI over 25. Advanced or distant metastatic stage, receiving neoadjuvant therapy, history of receiving antibiotics within prior 3 months, history of immunodeficiency, having a remote infection and history of reaction to treatment antibiotics are within the exclusion criteria.

INTERVENTIONS All patients are followed for 30 days postoperatively (once in a week at the original surgical unit). Patients and the investigator who inspects all wounds are blinded. The cost of prophylactic antibiotics are compared to the cost of infection treatment (inc. wound care, further antibiotic treatments, hospital visits) in patients who develop SSI.