Locally applied antibiotics may improve outcomes for women who undergo implant-based breast reconstruction

Disease and treatment 24. mar 2024 3 min Research Group Leader and Associate Professor Mikkel Herly Written by Kristian Sjøgren

Many women experience infection around their implant when they undergo breast reconstruction following breast cancer. Now a new study shows that applying antibiotics locally on the implant and in the implant pocket protects against infection for up to seven days.

Women may choose to have their breasts reconstructed following breast cancer treatment, and this typically involves implants.

However, after reconstruction, 5–10% of women develop an infection involving the breast implant that requires surgically removing the implant and rescheduling the breast reconstruction – a process that can be long and painful for the patient.

Surgeons have several options to avoid infection, including administering prophylactic systemic antibiotics before surgery and antibiotic therapy in the days and weeks following surgery.

Another option is to administer antibiotics directly onto the breast implant and in the implant pocket – an option favoured by most plastic surgeons in the United States. However, it is not known for how long the locally applied antibiotics protects against infection.

Now a new study shows that applying antibiotics locally may be a very good idea, since the local concentration of antibiotics is sufficient to keep infections at bay for up to one week.

The study is part of a larger project in which researchers and surgeons will determine whether applying antibiotics locally can reduce the risk of implant infection for which the implants have to be surgically removed.

“There are different approaches to this problem in different parts of the world. In many places, surgeons have started to administer antibiotics locally to reduce the risk of infection, but we do not know for how long a specific application of antibiotics can effectively prevent infection. Our study determined this and indicates what to expect in a large study involving 1,000 women who undergo implant-based breast reconstruction following treatment for cancer,” explains a researcher involved in the study, Mikkel Herly, Research Group Leader and Associate Professor, Department of Immunology and Microbiology, University of Copenhagen and MD at the Department of Plastic Surgery, Rigshospitalet, Copenhagen.

The research, which was carried out by doctor and PhD Fellow Mathilde Hemmingsen and others, has been published in JAMA Network Open.

Forty women received locally applied antibiotics

Forty women who underwent implant-based breast reconstruction after breast cancer participated.

The women received vancomycin, gentamicin and cefazolin applied to the implant surface and in the implant pocket, the same antibiotic combination that has been found to be effective in vitro.

Then the researchers measured the concentrations of the three types of antibiotics in the drain fluid from the women’s surgical drains at random time points for up to 10 days after the surgery.

The concentrations of vancomycin and gentamicin are especially interesting, since they protect against Staphylococcus aureus and Pseudomonas aeruginosa, respectively, which are often involved in implant infections that lead to surgical removal.

“You can apply antibiotics locally, but before this study we did not know how long the concentrations of antibiotics remained sufficiently high to be effective – whether it was days or just hours. This would have considerable implications for our strategy to prevent implant infections with antibiotics,” says Mathilde Hemmingsen.

Antibiotics effective for seven days

The results indicate that applying antibiotics on the implant and in the implant pocket effectively prevents infection.

To the researchers’ surprise, the concentration of vancomycin in the drain fluid was still effective after seven days, exceeding the minimum inhibitory concentration for the most common bacterial infections. In this context, seven days is a long time in which the body can heal undisturbed.

However, the concentration of gentamicin was only effective for around 24 hours following surgery and cefazolin for slightly more than three days.

The researchers also examined the women’s blood and found no measurable concentrations of antibiotics even though they had received relatively high doses of antibiotics in the implant pocket.

“This indicates that we can probably increase the dose of antibiotics in the implant pocket without increasing the risk of side-effects. Examining the possibility of increasing the concentration of gentamicin will be especially useful to protect these women from infections with Pseudomonas aeruginosa. The current dosage already appears to be sufficient to protect against Staphylococcus aureus,” notes Mikkel Herly.

Study recruiting 1,000 women

Mikkel Herly explains that the results of this small study are not enough to guide the treatment guidelines in this field.

This requires that the researchers show that the approach of applying antibiotics to implants in breast reconstruction leads to effective concentrations in the implant pocket but also leads to better treatment outcomes, with fewer infections requiring surgical removal.

The researchers are conducting such a study: the BREAST-AB trial (Prophylactic Treatment of Breast Implants with a Solution of Gentamicin, Vancomycin and Cefazolin Antibiotics for Women Undergoing Breast Reconstructive Surgery: a Randomized Controlled Trial). This randomises 1,000 women who have undergone implant-based breast reconstruction following cancer – and applies either three types of local antibiotics or saline solution in the breast implant pocket.

The researchers then monitor the women to determine whether the number of implant infections differs. Six hundred women have already been included.

“This study will be decisive in determining how to avoid implant infection among women who have undergone implant-based breast reconstruction. We hope that this may contribute to fewer women developing infection following surgery requiring removal,” concludes Mikkel Herly.

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