Cancer is a major cause of morbidity and mortality worldwide, with incidence rates that vary widely depending on geographic location, age, sex and race. Low- and middle-income countries have a proportionally higher burden of cancer than high-income countries, but their health systems are not prepared to deal with this problem .
For Brazil, it is estimated that 11.200 new cases of oral cavity cancer in men and 3.500 in women are estimated for each year of the 2018–2019 biennium. These numbers correspond to an estimated risk of 10.86 new cases per 100.000 men, ranking fifth; and 3.28 for every 100.000 women, being the 12th most common among all cancers14. Of these patients, it is common to develop oral side effects as a result of the treatment to which they are submitted, since changes in the oral microbiota, changes in physiological functions and/or important structural changes are inherent to the treatment and end up causing side effects such as: xerostomia, osteoradionecrosis, candidiasis, mucositis, among other several found in the literature [15–17].
The most important side effects of antineoplastic therapy in the past are vomiting and decreased immunity due to myelosuppression, however, due to the use of antibiotics and the use of hematopoietic agents, vomiting and immune compromise have been greatly reduced [15–17]. However, mucositis has recently emerged as one of the most serious side effects in cancer treatment [4, 5]. When oral mucositis develops during cancer treatment, it can lead to dysphagia, pain, changes in taste, vomiting, nausea, decreased food intake, fatigue and weight loss, in addition, discontinuation of therapy due to mucositis can lead to an extension of the period of the same, which can affect the result obtained or in the deterioration of the quality of life [4, 5]. The purpose of rehabilitation is to restore the patient to normal life, promoting the recovery of physical, emotional, mental and social function.
When analyzing the results achieved, it is observed that the two treatments reduced Candida yeast in the last two evaluations (21 days and 30 days), but not in the first two (7 days and 14 days). However, intergroup comparisons indicated that the average percentage of yeast reduction of the genus Candida after the application of therapies was significantly higher in the aPDT group in all four assessments (7, 14, 21 and 30 days).
Regarding the antimicrobial efficacy of aPDT, many studies have shown promising results, often reaching inactivation rates of more than 5 log10 CFU, which is understood as a disinfectant effect according to infection control guidelines. Data suggest that photodynamic therapy is potentially effective against bacterial, viral, fungal and protozoal infections [19–22]. The in vitro mechanism of action described in some studies shows that this therapy induces the generation of reactive oxygen (ROS) and nitrogen species, which effectively damage a variety of fungal cell structures and induce cell death [23–25].
The intra-group comparisons demonstrated that the control and aPDT groups showed a significant difference in the degree of mucositis over the four evaluations carried out, with the results pointing out that the mucositis worsened in the control group from the 14th day, while reduced in the aPDT group from the 21th day of treatment. Intergroup comparisons indicated statistical difference in the third (21 days) and fourth (30 days) evaluations, with the results showing that, compared to the control group, the LLLT group had a lower degree of mucositis in the last evaluation (30 days) and the aPDT group in the last two evaluations (21 and 30 days). No statistical differences were observed between the LLLT and aPDT groups in the degree of mucositis, demonstrating that both therapies are effective in the treatment of mucositis.
A Systematic Review and Meta-Analysis conducted in 2014 demonstrated that prophylactic LLLT reduces the overall risk of severe mucositis and other measures of mucositis severity, including the duration of severe mucositis in cancer patients and those undergoing aPDT . Numerous studies carried out by scientists have shown that LLLT normalizes microcirculation, activates endothelocytes, stimulating their functional activity by dilating and opening reserve capillaries, providing oxygen access to epithelial cells and promoting activation of cell metabolism . Different studies have described a decrease in the incidence and severity of mucositis, apparently due to accelerated regeneration and affected tissue healing, thereby reducing inflammation and pain . The application of LLLT accelerates oral reepithelization, favorably influencing the results of oral mucositis in patients undergoing hematopoietic stem cell transplantation and myeloablative chemotherapy .
The results of the intra-group comparisons indicated that all three groups showed a statistical difference in the pain score over the four evaluations performed, with the results demonstrating that in the LLLT group there was pain reduction after 21 days of treatment, while in the aPDT group this effect was observed earlier (14 days); in the control group there was a reduction in pain in the third assessment (21 days), followed by an increase in the last assessment (30 days). Intergroup comparisons showed a greater analgesic effect of treatments with LLLT and aPDT at the end of the study (30 days), compared to the control group. The results presented here clearly demonstrate the effectiveness of these treatment modalities, proving to be a valid option for improving patients' quality of life.
Pain associated with mucositis often impairs functional status, this painful side effect reduces quality of life and often requires narcotic analgesia, enteral or parenteral nutrition at additional costs .
It is noteworthy that, to date, a large number of reliable studies, which prove the effectiveness of LLLT in the treatment of mucositis after chemotherapy, have been published, and they report a reduction in the likelihood of complications, in the severity of the disease and in the pain level. The preventive use of LLLT does not allow oral mucositis to develop, significantly reducing the cost of maintaining patients in the hospital and the total cost of treatment, the high efficiency of LLLT being explained by numerous mechanisms of laser biomodulation .