Photobiomodulation in the Prevention and Management of Oral Mucositis in Children

Inclusion Criteria:

Prevention Arm - Inclusion Criteria

* Age 4 to 17 years
* Histopathologic diagnosis of malignant neoplasm: leukemia, lymphoma, or solid tumor of the head and neck.
* Within days 1-3 of the start of any chemotherapy cycle; for leukemia patients, in consolidation phase as defined by protocol.
* No signs of oral mucositis at enrollment.
* Availability and willingness to attend scheduled photobiomodulation (PBM) application sessions.
* Parent/legal guardian signed informed consent and child assent when applicable (≥ 8 years).
* No documented primary immunodeficiency.
* No severe concomitant systemic infection or medical condition that, in the investigator's judgment, contraindicates participation.
* No PBM treatment within 14 days prior to enrollment.
* No history of adverse reactions to light therapies or known photosensitivity.
* No history of seizure disorder or diagnosis of epilepsy.

Treatment Arm - Inclusion Criteria

* Age 4 to 17 years
* Histopathologic diagnosis of malignant neoplasm: leukemia, lymphoma, or solid tumor of the head and neck.
* Currently receiving chemotherapy (any cycle of the regimen).
* Presence of oral mucositis of any grade during chemotherapy, identified within the first 3 days from onset of the mucositis episode.
* Parent/legal guardian signed informed consent and child assent when applicable (≥ 8 years).
* No documented primary immunodeficiency.
* No severe concomitant systemic infection or medical condition that, in the investigator's judgment, contraindicates participation.
* No photobiomodulation (PBM) treatment within 14 days prior to enrollment.
* No history of adverse reactions to light therapies or known photosensitivity.
* No history of seizure disorder or diagnosis of epilepsy.

Exclusion Criteria:

* Documented primary immunodeficiency.
* Severe concomitant systemic infection or unstable medical condition.
* PBM treatment within 14 days prior to enrollment.
* Known photosensitivity or prior adverse reaction to light therapy.
* History of seizures or epilepsy.
* Any condition that, in the investigator's opinion, would interfere with study participation or safety.

Participant Withdrawal Criteria

* Attendance to fewer than 80% of scheduled treatment sessions.
* Any adverse event or persistent discomfort attributed to PBM that leads the participant or guardian to decline further intervention.
* Withdrawal of consent by parent/guardian or assent withdrawal by participant when applicable.
* Development of a new medical condition that, per investigator judgment, contraindicates continuation.