Breast cancer is one of the most common cancers in metropolitan France, with over 60,000 new cases in 2023. Mostly a female cancer, it can affect a young population, with around 20% of breast cancers occurring in women under 50. Treatment is mainly based on surgery, chemotherapy, radiotherapy, targeted therapies and hormone therapy. Although chemotherapy is not systematically used, it remains a frequent treatment option. While chemotherapy makes a major contribution to curing cancer, it is also a source of potentially disabling side effects for survivors.

Chemotherapy can interfere with the normal functioning of the central nervous system, leading to cognitive impairment. The number of people potentially affected by chemobrain is estimated at several tens of millions worldwide. There is no recommended treatment for people with chemobrain. Several avenues have been explored, with very limited results. Photobiomodulation (PBM) is a non-medicinal treatment technique that combines all the biological, athermic and non-cytotoxic effects of tissue exposure to non-ionizing sources of red and infrared light. Several studies have demonstrated the beneficial effects of cortical stimulation by photobiomodulation on memory (increased angiogenesis, increased oxygenation of brain tissue via vasodilatation, and increased mitochondrial ATP production). These positive biological effects are likely to ameliorate the undesirable effects of chemotherapy, and consequently the post-chemotherapy cognitive disorders that ensue.

Inclusion Criteria:

• Women aged 18 and over
• Having completed chemotherapy (intravenous) for breast cancer (any stage) less than 12 months prior to inclusion
• Having a perceived cognitive complaint that appeared during or after (< 3 months) chemotherapy treatments (no restriction on the care protocol used) and confirmed by a FACT-Cog score compatible with a subjective cognitive disorder (score < 117 for patients aged 18 to 49; score < 113 for patients aged 50 to 69; score <105 for patients aged 70 and over)
• Patient eligible for photobiomodulation sessions
• Patient with sufficient command of the French language to complete the study questionnaries
• Patient having given written consent to participate in the trial
• Socially insured patient
• Patient willing to comply with all study procedures and duration

Exclusion Criteria:

• Known cognitive disorders prior to chemotherapy treatment
• Patients with psychiatric or psychobehavioral disorders incompatible with photobiomodulation sessions
• Patients who, in the 12 months prior to inclusion or at the time of inclusion, have already received photobiomodulation treatment involving "whole body" therapy (photobiomodulation in a phototherapy booth).
• Patient having previously received photobiomodulation with cortical stimulation (panel or helmet) with no time limit.
• Patient taking or having received capecitabine
• Patients taking part in a protocol involving a drug likely to affect cognitive performance (on the investigator's advice).
• Patients suffering from claustrophobia
• Patient unable to read and/or unable to complete a questionnaire, in the opinion of the investigator

Women aged 18 years and over