AuthorisedTherapeutic confirmatory (Phase III)Interventional

PROPHY-SEIN - Evaluation of the effect of antibiotic prophylaxis during lumpectomy for breast cancer: prospective randomised double-blind noninferiority study of placebo vs cefazolin

Breast-conserving surgery, also known as a lumpectomy, is a common operation to remove breast cancer while keeping as much healthy breast tissue as possible. Right now, doctors often give patients an antibiotic through a drip just before surgery to stop wound infections from developing. However, taking antibiotics when they might not be needed can cause side effects and leads to antibiotic resistance, which makes bugs harder to treat in the future. This trial, called PROPHY-SEIN, aims to find out if it is safe to carry out lumpectomies without routine antibiotics. Women taking part will be randomly chosen to receive either the antibiotic cefazolin or a simple salt-water drip (placebo) at the time of their surgery. The medical team will then track their recovery for 30 days to see if wound infection rates remain low in both groups.

At a glance

Status

Authorised

Phase

Therapeutic confirmatory (Phase III)

Sponsor

University Hospital Of Clermont-Ferrand

Enrolment target

1,600

Start

16 Jul 2026

Breast Cancer

What is this study about?

When people have surgery to remove breast cancer while saving the rest of the breast—an operation called a lumpectomy or partial mastectomy—surgeons take great care to keep everything clean. Even so, it is common practice in many hospitals to give patients a single dose of an antibiotic through a vein just before the operation. The goal is to stop bacteria from causing a surgical wound infection.

While antibiotics are life-saving medicines, using them when they might not be strictly necessary carries downsides. They can cause upset stomachs, allergic reactions, and contribute to antibiotic resistance—where bacteria learn to survive the medicines designed to kill them. Because breast surgery is considered a very clean type of operation, doctors want to know if routine preventive antibiotics are actually needed, or if patients heal just as well without them.

This trial compares the antibiotic cefazolin against a harmless salt-water solution (placebo). Neither you nor your surgical team will know which one you receive. Over the first month after surgery, doctors will carefully check your healing, noting any redness, swelling, or infection, to find out if avoiding antibiotics is just as safe as using them.

Key takeaways

The trial tests whether routine antibiotics are truly needed during lumpectomy breast surgery.
Participants receive either a single dose of an antibiotic (cefazolin) or a salt-water dummy drip (placebo).
You will be closely monitored for 30 days after surgery to check how your wound heals.
If an infection occurs, it will be treated promptly with standard medical care.
Taking part is voluntary and will not delay your planned cancer treatments.

Who may be eligible?

This study is open to adult women who are scheduled to have a lumpectomy or partial mastectomy to treat breast cancer. This includes women having a simple lumpectomy, as well as those who are also having a lymph node checked or who have a tiny wire placed in the breast before surgery to guide the surgeon.

To take part, you must be aged 18 or older. Because the study focuses on breast-conserving surgery for cancer, people having other types of procedures, such as a full mastectomy or purely cosmetic breast surgery, will not be suitable for this trial.

Your hospital team will also review your overall health, including whether you have any known allergies to cefazolin or similar antibiotics, and whether you currently have an active infection that already requires antibiotic treatment.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am a woman aged 18 or older.
I have been diagnosed with breast cancer.
I am scheduled to have a lumpectomy or partial mastectomy.
I do not have a known severe allergy to cefazolin or similar antibiotics.
I am not currently taking antibiotics for an existing infection.

Answer every question to see your result.

What does participation involve?

Taking part in this study fits naturally around your planned surgery. On the day of your operation, an intravenous drip will be set up as normal. You will be given either the antibiotic cefazolin or a harmless salt-water solution just before surgery begins. You will not have to take any extra pills or schedule extra trips just for the medication.

During your hospital stay, the care team will monitor your surgical wound and note how quickly you recover. If you develop any signs of an infection, doctors will treat you promptly with standard care, which may include prescribed antibiotics.

Your participation continues for about 30 days after your operation. During this time, the researchers will check on your wound healing—usually at your regular post-surgery follow-up appointments. They will also record when you are ready to begin any next treatments, such as radiotherapy or chemotherapy.

Potential risks and benefits

Taking part may not give you a direct personal health benefit, but your participation could help spare future patients from unnecessary medicines and side effects. If you receive the antibiotic, there is a small risk of mild side effects like nausea, a rash, or rarely, an allergic reaction. If you receive the salt-water drip, there is a possibility you could develop a wound infection, although you will be watched very closely and treated immediately if this happens. Joining the study is completely your choice, and you can withdraw at any time without it affecting your cancer care.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
France

Common questions

What is a placebo?

A placebo is an inactive treatment that looks identical to the real medicine. In this trial, it is a simple, harmless salt-water drip containing no active drugs.

What happens if my wound gets infected during the study?

Your safety comes first. If your surgical wound shows any signs of redness, heat, or infection, your medical team will treat it straight away with standard antibiotics and wound care.

Will taking part delay my cancer treatment?

No. The study only looks at the single dose of medicine given at surgery and your 30-day recovery. It will not delay your surgery or any planned follow-up treatments like radiotherapy.

Can I choose whether I get the antibiotic or the salt water?

No. A computer randomly decides which group you join. This ensures the results are fair and scientifically reliable.

Will my doctors know which drip I received?

No. This is a 'double-blind' study, meaning neither you nor your doctors know which one you received. However, in a medical emergency, doctors can find out instantly.