The study was terminated due to difficulties in including patients because of the slow rate at which patients met the established treatment profile at the proposing institution.

Oral mucositis is the most significant acute toxicity of oral cavity radiotherapy. The available scientific evidence supports its preventive and therapeutic approach with low-level laser; however, this is unsuitable for tumor regions due to the risk of stimulating cellular metabolism. In this sense, an alternative treatment becomes necessary. Based on the preliminary results of the phase I study, a double-blind, randomized phase II study is suggested to evaluate the effectiveness of copaiba-based mouthwash in the prevention of oral mucositis in patients undergoing radiotherapy for oral cavity tumors. Patients will be randomized into 2 groups: A (copaíba) and B (placebo) and will use the mouthwash 4x/day. Each group will have 20 patients and be blind to the group in which they are included. They will be evaluated daily by a dental surgeon about oral mucositis, pain in the oral cavity and oropharynx, and dysphagia and will undergo daily laser therapy sessions, until the end of radiotherapy.

Oral cavity cancer represents the 8th most common type in Brazil, with an estimated 15,100 new cases for each year of the 2023-2025 period. It depends on the patient's clinical condition, tumor location, and staging, involving surgery, chemotherapy (CT), or radiotherapy (RT), alone or in combination. RT involves doses between 50 and 70 Gy and, in addition to the action on the tumor, it produces toxicity in adjacent tissues, compromising the patient's quality of life.

Oral mucositis (OM) is the most significant acute toxicity related to RT associated or not with CT for tumors in this location.7,8 Its preventive and therapeutic approach has been proposed in several ways, but for RT of oral cavity tumors, it has There is evidence for the use of low-level laser therapy (LBP) and benzydamine hydrochloride. However, benzydamine hydrochloride is effective for those who received RT doses of up to 50 Gy, and the application of LBP in the tumor region is contraindicated as its effect is due to the activation of receptors of the respiratory chain, causing stimulation of cellular metabolism. Therefore, OM conditions tend to be severe in these locations, especially in patients with oral tumor lesions. In this sense, the need for an auxiliary treatment method becomes evident.

A phase I study with copaiba (CPB) in patients with oral cancer undergoing RT was previously developed by this group. In this case, the use of the mouthwash did not trigger dose-limiting toxicity in any of the treated patients, allowing us to conclude that the maximum tested dose of 15% used 4 times/day is safe for the development of a phase II study. None of the patients reported pain or burning related to the use of mouthwash in the absence of OM lesions, suggesting that it is safe and non-toxic for this use. The preliminary assessment of the effectiveness of the mouthwash showed the occurrence of OM lesions in 89.5% of patients, at most grade 3; None of the patients evaluated developed grade 4 mucositis lesions according to the WHO scale. None of the patients evaluated in the study needed to interrupt RT or QT due to OM injuries.

OBJECTIVES Main objective: to evaluate the effectiveness of copaiba-based mouthwash in preventing and treating oral mucositis in patients with oral cancer undergoing radiotherapy.

Secondary objectives: evaluate the safety of copaiba mouthwash in patients who use it; compare the incidence of oral mucositis in tumor and non-tumor areas in the two groups; compare the oral cavity pain index in the two groups; compare the oropharyngeal pain index in the two groups; compare the dysphagia index in the two groups.

Inclusion Criteria:

• Patients aged 18 years or older;
• Patients enrolled at INCA diagnosed with malignant neoplasms located in the oral cavity or oropharynx with an extension of the lesion to the oral cavity (IDC-10 C01 to C06 or IDC10); with the indication of exclusive RT (using the Intensity Modulated Radiotherapy (IMRT)/ Volumetric Modulated Arcotherapy (VMAT) technique) or combined with surgery and/or CT;
• Patients with expected RT doses between 50 and 70Gy;
• Patients capable of understanding and adhering to the protocol;
• Patients capable of performing the oral hygiene protocol;
• Patients who, after the information and instructions, can provide the free and informed consent form.

Exclusion Criteria:

• Patients who are receiving drugs for the treatment and/or prevention of OM;
• Patients undergoing RT with planning that excludes the oral cavity from the irradiation field;
• Patients who report any allergy to CPB-based compounds.

Participants will be blind to the group in which they are included, as will the study team. The non-blind team will be composed of the pharmacy team, that will be responsabli for the randomization and for dispensing of the investigational product/placebo.