Setting: Oral mucositis is a very common complication of cancer treatment, accounting, often at increased risk for infections and even the interruption of treatment, interfering with the prognosis of the disease. The low intensity laser therapy has been proposed as an alternative for the treatment and prevention of this side effect, with good results in terms of clinical and functional, speeding up the process of wound healing and reducing pain.

Objective: To evaluate the effectiveness of using low power laser in the prevention of oral mucositis in patients with hematological cancer, undergoing chemotherapy for bone marrow transplantation.

Methods: There will be a Clinical Trial Randomized, double-blind study to evaluate the effectiveness of using low power laser in the prevention of oral mucositis in patients with hematological cancer, undergoing chemotherapy for bone marrow transplantation. Participate in the study, patients who are in the condition mentioned above accepting participate and have aged over 18. Will be excluded from the study patients who have autoimmune disease, which present sensitivity to laser or who have already started treatment for oral mucositis prior to this study.The study variables are:-independent variable: whether or not the red laser of low power-dependent variables: oral mucositis, degree of mucositis, chemotherapy regimen, type of blood cancer. For determining the association between the independent variable and the dependent will be used chi-square tests of association (Pearson) and Fisher's exact test, if necessary. Will calculate the risk ratio (RR) as a measure of relative risk, with the confidence interval at 95% (IC95%).Also be calculated NNT (number needed to treat to obtain benefit) and NNH (number needed to harm getting). Will be adopted a significance level of 5%. The project was approved by the Ethics and Research iMIP. All patients will be appropriately informed about the objectives of the project and will only be included if they voluntarily agree to participate by signing the consent form.

Keywords: laser, prevention and control; oral mucositis, bone marrow transplant.

Inclusion Criteria: patients with blood cancers undergoing chemotherapy for

BMT; patients who agree to participate; patients older than 18 years.

Exclusion Criteria: patients with autoimmune diseases; patients who have sensitivity to the laser; patients who have already started treatment for mucositis prior to the research; HIV-positive patients.

Inclusion Criteria:

• patients with hematologic cancers undergoing chemotherapy for

BMT;

• patients who agree to participate;
• patients older than 18 years.

Exclusion Criteria:

• patients with autoimmune diseases;
• patients who have sensitivity to the laser;
• patients who have already started treatment for mucositis prior to research.