Do antibiotics prevent surgical site infection after breast cancer surgery?

What was the aim of this review?
The aim of this review was to determine whether giving people antibiotics before or during an operation is effective for preventing surgical site infection (SSI) following breast cancer surgery. Researchers from Cochrane collected and analysed all relevant studies (randomised controlled trials) to answer this question and found 11 relevant studies. Randomised controlled trials are medical studies where people are chosen at random to receive different treatments. This type of trial provides the most reliable health evidence.

Key messages
There is moderate certainty evidence that antibiotics given before an operation probably reduce the risk of SSI in patients having surgery for breast cancer. We cannot be certain whether antibiotics given during an operation reduce the risk of developing an SSI, as the available evidence is of very low certainty.

What was studied in this review?
Breast cancer is the most common cancer affecting women and the leading cause of cancer death in women. Surgical removal of all or part of the breast is a common treatment for people diagnosed with breast cancer. However, an infection of the surgical wound is often a complication of the surgery, affecting up to 15% of patients. Having an SSI may require a longer stay in hospital or a repeat operation. Taking antibiotics prior to the operation or during the operation aims to reduce the risk of developing an infection in the surgical wound.

What are the main results of the review?
In August 2018 we searched for randomised controlled trials that investigated whether antibiotics given to people before or during surgery for breast cancer prevent an infection of the surgical site (SSI). This is an update of an existing review and no new relevant studies were found in the most recent search. We analysed the results of 11 studies with 2867 participants. Ten studies looked at giving antibiotics to patients prior to the surgery compared with not giving antibiotics or giving placebo. One study compared giving antibiotics perioperatively (between induction of anaesthetic and the patient leaving the recovery room) to not giving antibiotics. The results showed us that giving antibiotics before surgery probably reduced the risk of developing surgical site infection in patients undergoing breast cancer surgery with moderate certainty. No conclusions can be made from the results of the single study comparing perioperative antibiotics to no antibiotics as the evidence is of very low certainty. It is very uncertain whether there is an effect on incidence of adverse events. Furthermore, the effects on time to onset of infection, readmission to hospital and cost of care remain unclear. The review is not able to establish which antibiotic is most appropriate.

How up to date is this review?
We searched for studies that had been published up to August 2018.

Authors' conclusions: 

Prophylactic antibiotics administered preoperatively probably reduce the risk of SSI in patients undergoing surgery for breast cancer. However, it is very uncertain whether there is an effect on incidence of adverse events. Furthermore, the effects on time to onset of infection, readmission to hospital and cost of care remain unclear. Further studies are required to establish the best protocols for clinical practice.

Read the full abstract...
Background: 

Surgery has been used as part of breast cancer treatment for centuries; however any surgical procedure has the potential risk of infection. Infection rates for surgical treatment of breast cancer are documented at between 3% and 15%, higher than average for a clean surgical procedure. Pre- and perioperative antibiotics have been found to be useful in lowering infection rates in other surgical groups, yet there is no consensus on the use of prophylactic antibiotics for breast cancer surgery. This is an update of a Cochrane Review first published in 2005 and last updated in 2014.

Objectives: 

To determine the effects of prophylactic (pre- or perioperative) antibiotics on the incidence of surgical site infection (SSI) after breast cancer surgery.

Search strategy: 

For this fourth update, in August 2018 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase; and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.

Selection criteria: 

We included randomised controlled trials of pre- and perioperative antibiotics for patients undergoing surgery for breast cancer. Primary outcomes were rates of surgical site infection (SSI) and adverse reactions.

Data collection and analysis: 

Three review authors independently examined the title and abstracts of all studies identified by the search strategy, then assessed study quality and extracted data from those that met the inclusion criteria. We contacted study authors to obtain missing information. We evaluated the certainty of evidence using the GRADE approach. We used standard methodological procedures expected by Cochrane.

Main results: 

A total of 11 randomised controlled trials (2867 participants) were included in the review. No new studies were identified in this update. All studies included breast cancer patients and were based in the hospital setting. Ten studies evaluated preoperative antibiotic compared with no antibiotic or placebo. One study evaluated perioperative antibiotic compared with placebo or no antibiotic. Pooling of the results demonstrated that prophylactic antibiotics administered preoperatively probably reduce the incidence of SSI for patients undergoing breast cancer surgery without reconstruction (pooled risk ratio (RR) 0.67, 95% confidence interval (CI) 0.53 to 0.85; moderate certainty evidence). Anticipated absolute effects were calculated for the outcome incidence of SSI; 105 per 1000 for the none or placebo group and 71 per 1000 (95% CI 56 to 89) for the preoperative antibiotic prophylaxis group. Analysis of the single study comparing perioperative antibiotic with no antibiotic was inconclusive for incidence of SSI (RR 0.11, 95% CI 0.01 to 1.95; very low certainty evidence). No studies presented separate data for patients who underwent reconstructive surgery at the time of removal of the breast tumour.

Secondary outcomes were not consistently included in the studies investigating preoperative antibiotic prophylaxis. It is very uncertain whether there is a difference in incidence of adverse events between the treatment and no treatment or placebo groups (10 studies, 2818 participants); very low certainty evidence downgraded one level for serious risk of bias, one level for serious inconsistency and one level for serious imprecision. It is unclear whether there is a difference in time to onset of infection between the treatment and no treatment or placebo groups (4 studies, 1450 participants); low certainty evidence downgraded one level for serious risk of bias and one level for serious inconsistency. It is unclear whether there is a difference in rates of readmission to hospital between the treatment and placebo groups (3 studies, 784 participants); low certainty evidence downgraded one level for serious inconsistency and one level for serious risk of bias. It is unclear whether there is a difference in cost of care between the treatment and no treatment or placebo groups (2 studies, 510 participants); low certainty evidence downgraded one level for serious risk of bias and one level for serious inconsistency. No analysable secondary outcome data were reported for the single study evaluating perioperative antibiotics.

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