For a young patient, the conditions of proton therapy treatment can be stressful. Adjusting the environment can be a source of avoiding this physical and psychological discomfort impacting the quality of treatment.

A fixed, long, uncomfortable position is the main cause of stress, already present due to the cancerous therapeutic course. It extends the positioning time. For the patient and the optimization of his treatment, solutions must be sought.

Relaxation in virtual reality is efficient, simple and non-medicinal and could reduce stress in children and allow irradiation in very good conditions.

We will assess the effectiveness of the virtual reality session using objective (placement time, helmet tolerance) and subjective (perceived anxiety via a dedicated questionnaire) criteria. This is the first pediatric virtual reality study, supported by the French Group of Pediatric Radiotherapists, to reduce anxiety in radiotherapy.

Multiple benefits from this pilot study are expected, such as improved reception conditions, treatment parameters and better acceptance of proton therapy sessions.

The treatment of certain pediatric cancers requires irradiation. These treatments are stressful in children because it is necessary to keep a fixed position that is often uncomfortable. The more the stress increases, the longer the positioning, which again generates stress making the treatment position more and more uncomfortable. This irradiation can be carried out by various conventional techniques, tomotherapy, proton therapy. In all cases, the precise positioning, essential for the successful completion of the treatment, under the treatment machine is an iterative process, requiring long and tedious checks. This positioning step on the treatment table takes about 15 minutes, but depending on the technical difficulty can be extended up to 45 minutes in the most complex cases and depending on the patient's apprehension. This positioning is then checked by placement verification images.

At the Antoine LACASSAGNE Center, the investigators have a new generation proton therapy device. This device allows radiotherapy doses to be delivered extremely precisely, subject to very rigorous positioning, and is therefore particularly suitable for pediatric treatment by protecting organs near the radiation. In addition, proton therapy requires longer sessions than conventional radiotherapy; which generates even more anxiety for the children for whom it is the treatment of choice. Non-drug solutions to reduce this stress are therefore necessary to allow the irradiation to be carried out under optimal conditions in order to ensure the effectiveness and safety of the treatment. In this context, virtual reality (VR) headsets, using relaxation techniques in virtual reality or digital sedation, are presented as a simple solution to reduce the anxiety of children regarding the treatment and would therefore be tested mainly on this modality.

To allow us to assess the effectiveness of this technique on anxiety, the investigators will therefore measure the positioning time necessary before carrying out a treatment session and its reduction via its impact on perceived anxiety thanks to a dedicated questionnaire.

The strength of our study is that it uses simple and reproductive measurement systems such as the measurement of placement time and a validated anxiety scale during Marie POURCHET's science thesis. This is the easy EVAN (Anxiety Assessment) scale adapted to several age groups and developed in pediatric wards.

Inclusion Criteria:

• Patient treated at the Antoine LACASSAGNE Center for treatment by proton therapy
• Age ≥ 7 years old and ≤ 18 years old
• Patient, and parents for minor children, having read the information notice and signed the informed consent,
• Patient with social security coverage.

Exclusion Criteria:

• Age < 7 years old and > 18 years old,
• Patient under general anesthesia,
• Patient suffering from wounds or infections in the head, deemed incompatible with the use of the helmet by the investigator,
• Patient suffering from respiratory problems,
• Patient suffering from a high level of claustrophobia,
• Patient followed for a psychiatric pathology,
• Patient suffering from unbalanced epilepsy,
• Patient suffering from visual (binocular vision) and / or hearing disorders preventing the use of virtual reality,
• Patient whose head circumference is insufficient for the use of the helmet, deemed incompatible with the use of the helmet by the investigator,
• Patient treated by radio chemotherapy.