Inclusion Criteria:

• Patient has provided written informed consent using the PBM PICF
• Age ≥ 18 years of age at Screening
• Histological diagnosis of HNC of the oral cavity with no evidence of macroscopic or microscopic residual disease post-surgery (R0 or R1 resection) with histopathological confirmation and no gross residual lymphadenopathy in the planned PBM treatment area
• Planned treatment with RT or chemoradiotherapy to a dose of ≥ 50 Gy Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 (Appendix 1)
• Intact oral mucosa (no visible ulceration, dehiscence, or active infection)

Exclusion Criteria:

• Gross macroscopic and/or microscopic residual disease post-surgery (R2 resection) or gross residual lymphadenopathy in the planned PBM treatment area
• Prior RT to the head and neck including the oral or oropharyngeal mucosa
• Prior cytotoxic chemotherapy in the last 3 months
• Diagnosis of photosensitive disorder (cutaneous porphyria, xeroderma pigmentosum, etc)
• Concurrent administration of cetuximab
• Known to be pregnant or planning to become pregnant within the trial period
• Diagnosis of epilepsy