The goal of this clinical trial is to learn if hyperbaric oxygen therapy (HBOT) enhances fat graft survival in lipofilling procedures in irradiated breast cancer patients. The main questions it aims to answer are:

Does it improve fat graft survival ? Evaluate safety and tolerability of HBOT in this setting? Researchers will compare patient receiving HBOT to a control group without HBOT to see if.

Sixteen female patients will undergo two autologous fat grafting sessions: one with HBOT and one without, in a randomized sequence. Patients will undergo three MRI during the study to evaluate the fat retention rate.

This is a prospective, monocentric, randomized controlled phase II crossover clinical trial designed to evaluate the efficacy and safety of hyperbaric oxygen therapy (HBOT) in improving fat graft retention following autologous fat transfer (AFT) in breast reconstruction for patients with prior radiotherapy.

AFT is widely used in breast reconstruction but is often less effective in irradiated tissues due to reduced vascularization and oxygenation, which compromises graft survival. HBOT, which involves breathing 100% oxygen at 2.5 atmospheres absolute (ATA), has been shown to promote angiogenesis and tissue oxygenation, potentially improving fat graft integration and reducing complications in irradiated tissues.

The study will enroll 16 adult female patients who have undergone radiotherapy as part of their breast cancer treatment and are scheduled to receive two sessions of AFT. Each participant will be randomized to one of two sequences:

• Sequence AB: AFT alone (control) followed by AFT + HBOT (intervention)
• Sequence BA: AFT + HBOT followed by AFT alone HBOT will be administered in five sessions (1 on Day 0, 2 on Day 1, 2 on Day 2), beginning immediately after the fat grafting procedure. Each session consists of 100% oxygen inhalation at 2.5 ATA for 90 minutes. Postoperative MRI will be performed six months after each AFT session to assess the volume of retained graft.

Primary Objective:

To determine whether HBOT significantly improves fat graft retention in irradiated breast tissue, assessed as the percentage of volume retained (measured by MRI) six months postoperatively.

Secondary Objectives:

• To assess the absolute fat volume retention in milliliters
• To evaluate the safety and tolerability of HBOT in this setting
• To assess the incidence of clinical and radiological complications (e.g., infection, hematoma, oil cysts, liponecrosis) The crossover design minimizes inter-patient variability by allowing each patient to serve as her own control. Randomization occurs immediately after the first AFT session.

The anticipated duration of participation per subject is approximately 12 to 18 months, and the total study duration is estimated at 3 years (from November 2025 to November 2028).

Inclusion Criteria:

• Adult (18 y.o. or more) female patients considered for lipofilling following breast reconstruction in an oncological setting which received radiation therapy on the affected breast.
• Ability to provide informed consent, documented by signature

Exclusion Criteria:

• Pregnancy or breastfeeding
• Unability to provide informed consent
• Previous enrolment into the current investigation

Contra-indication to HBOT :

• Anamnestically reported spontaneous pneumothorax
• Status post-thoracotomy
• Significant intra-pulmonary lesions (including emphysematous bullae)
• Respiratory function disorders (both obstructive and restrictive syndromes)
• Pregnancy
• Major psychiatric disorders
• Uncontrollable claustrophobic reaction
• Seizures, even if treated and asymptomatic for some time
• Status post-severe traumatic brain injury with neurological deficits and seizures
• Decompensated heart failure
• Recent myocardial infarction (<6 months) or with persistent hemodynamic sequelae
• Spastic coronary angina
• Cardiac arrhythmias, atrioventricular block, Wolff-Parkinson-White syndrome, sinus node dysfunction, Lown-Ganong-Levine syndrome
• Cardiac pacemakers with unknown pressure resistance
• Severe bradycardia
• Sinus ostium displacement (acute or chronic)
• Displacement of the auditory canal entrance (acute or chronic)
• Status post-tympanoplasty type I-III <3 months
• Acute febrile state
• Optic neuritis
• Unstabilized hyperthyroidism

Contra-indication to MRI :

• Non-MRI-compatible pacemaker, cochlear implant, drug-infusion pump or neurostimulator.
• Metallic foreign body in critical area (eye, brain, etc.)
• Ferromagnetic vascular surgical clips of older generation, e.g., for intracranial aneurysm repair.

In order to protect patient's privacy and data.