Hyperbaric Oxygen Therapy (HBOT) is a treatment involving the administration of oxygen at pressures higher than atmospheric pressure, with numerous potential indications such as radiation-induced tissue damage, chronic wounds, and more. HBOT significantly increases the amount of dissolved oxygen in tissues, thereby promoting wound healing.

However, this "hyperoxygenation" may also exert toxic effects, particularly through the production of reactive oxygen species (ROS), which can induce DNA damage and potentially promote mutagenesis, thereby increasing long-term neoplastic risk.

A single HBOT session is associated with a significant increase in ROS production, which may persist for up to 48 hours post-exposure, and is also linked to DNA damage. DNA repair is typically a rapid process, with the activation of protective mechanisms.

The effects of repeated HBOT sessions remain a matter of debate. Reported outcomes range from attenuation of genotoxicity, to exacerbation of DNA damage, or no effect at all (8). In patients with cancer or comorbidities associated with impaired DNA repair capacity, repeated HBOT could be more detrimental, potentially increasing genotoxic effects and cancer risk. This increased oxygen susceptibility in cancer patients has already been observed in normobaric conditions during abdominal surgery, where hyperoxygenation strategies were associated with increased mortality in this subgroup.

A potential pro-carcinogenic effect of HBOT in cancer patients has also been suggested in some case series, though not confirmed by larger studies.

Current literature on HBOT safety remains generally reassuring; however, the possibility of DNA damage and its potential long-term genotoxic consequences cannot be entirely excluded. This question is of particular importance given that many primary indications for HBOT involve patients with a history of malignancy or active cancer

Inclusion Criteria:

• Adults (≥18 years old)
• Having signed an informed consent form
• Affiliated with or beneficiary of a national health insurance system
• Admitted to the hyperbaric medicine department for HBOT treatment
• Either for a complication related to prior radiotherapy (administered for an underlying neoplastic disease), such as:

Radiation cystitis Radiation proctitis / enteritis Radiation dermatitis Mandibular osteoradionecrosis Or for another indication, without any underlying neoplastic disease

Exclusion Criteria:

• Patients with a contraindication to hyperbaric oxygen therapy (HBOT)
• Pregnant, breastfeeding, or postpartum women
• Patients deprived of liberty by judicial or administrative decision
• Patients undergoing involuntary psychiatric treatment
• Patients under legal guardianship or protective custody