Head and neck cancer (HNC) are among the most frequent malignancies in the world. The main treatment modalities for HNC are surgical excision, radiotherapy (RT), and chemotherapy (CT). Severe oral sequelae such as oral mucositis (OM), dysgeusia, opportunistic infections, trismus, and xerostomia/hyposalivation can affect HNC patients due to oncological treatment with RT and QT. Photobiomodulation therapy (PBMT) with an intraoral low-power laser has been studied as an excellent tool in the management of OM and xerostomia and thus improves the tolerability of RT in the head and neck region. The aim of this multicenter, randomized, single-blind clinical trial is to compare the effects of two photobiomodulation protocols (intraoral application low-level laser and defocused extraoral application of high-power laser) in the management of oral mucositis (OM) and xerostomia in head and neck cancer patients undergoing radiotherapy (RT). It is expected defocused extraoral high-power photobiomodulation shows results as good as intraoral photobiomodulation on the management of oral mucositis.

Radiotherapy (RT) and chemotherapy-induced oral side effects, as oral mucositis, and xerostomia are extremely challenging for professionals in the supportive care for head and neck squamous cell carcinoma (HNSCC) patients. There is a substantial evidence about the benefits of photobiomodulation in the management of these oral side effects, mainly in the decrease of oral mucositis (OM) rates and OM severity, healing of OM ulcers and pain relief by intraoral low-level lasers. However, new parameters as extraoral applications by defocused high-power lasers have been investigated to improve the OM outcomes, the patients' complaints, and the experience in the clinical assistance by professionals. Thus, 132 H&N cancer patients will be, globally and simultaneously, randomized according to clinical stage of head and neck cancer, type of treatment (isolated RT or RT and QT), type of RT (RTC3D or IMRT) and center involved (A.C. Camargo Cancer Center or State of São Paulo Cancer Institute or Porto Alegre Clinics Hospital). The randomized patients can be allocated into two groups: Group I: intraoral photobiomodulation with low level laser therapy (660nm, 100 mW, 10 J/cm2, 3 s/point) and Group II: extraoral photobiomodulation with high level laser therapy (810 + 980 nm, 1000 mW, 6.11 J/cm2, 30 s/point). PBMT will be performed daily, 5 times per week during the radiotherapy or until wound healing of OM lesions by a trained professional. Oral mucositis, pain, xerostomia, dysphagia, dysgeusia, oral functions, labial hydration and radiodermatitis will be evaluated daily. Salivary flow and trismus will be assessed weekly, and two questionaries (OHIP-14 and Vanderbilt) will be assessed on the first day of RT, on the middle of RT regimen, on the final of RT regimen and three months later RT sessions.

Inclusion Criteria:

• Patients with a diagnosis of cancer in the oral cavity and oropharynx any clinical stage based on TNM staging of head and neck cancer;
• Patients who received oral care prior to oncological treatment;
• Patients who will receive conformational radiotherapy (RT-C3D) or Intensity-modulated radiotherapy (IMRT) from 50 Gy to 70 Gy (primary radiation field) in daily doses of 1.8-2, 12 Gy divided five times per week (from Monday to Friday), totalizing 6 to 7 weeks of treatment. They may receive exclusive RT or with chemotherapy concomitant with cisplatin (100 mg/m2 every 21 days or 50 mg/m2 per week);
• Patients feeding orally or by parenteral nutrition;
• Patients who agree to participate in the study after reading, filling, and signing the Consent Form for Participation in Clinical Research.

Exclusion Criteria:

• Patients who develop head and neck radiodermatitis and for this reason interrupt the survey;
• Patients who do not appear in four or more PBMT or RT sessions.

The outcomes assessor will not know the laser protocol of each patient.