Approximately 90% of patients with breast cancer who are treated with adjuvant radiotherapy develop acute skin reactions . Interventions to reduce this adverse side effect are needed since radiodermatitis may impact a patient’s adherence to treatment, and, with increased severity, can lead to the discontinuation of a potentially curative treatment [1, 2].
Acute radiodermatitis is a reaction caused by secondary skin exposure to ionizing radiation. Ionizing radiation impairs the ability of cells to proliferate quickly, and this leads to a skin reaction. This complex process involves DNA damage and changes in proteins, lipids, and carbohydrates. At the tissue level, this injury to the skin includes basal cell destruction and depletion of skin cells. As the migration of basal cells to the skin surface is compromised by radiation, flaking of the skin develops [1, 3]. Initially manifesting as erythema between the first and fourth weeks of radiation treatment, this condition can progress to ulceration up to three months after treatment [4, 5].
Known risk factors for radiodermatitis include total radiation dose, fractionation scheme, type of equipment used, volume of tissue irradiated (such as breast volume), and the radiosensitivity of the tissues involved. It is believed that patient-related factors, such as smoking habit, chronic diseases (including diabetes mellitus), and concomitant anticancer treatment can also interfere with skin reactions by affecting the healing process .
Prevention of this adverse event has been investigated in several studies [3, 7–9]. However, there is currently no clinically applicable prophylaxis available. As suggested by the Cancer Care Ontario Guidelines, the efficacy of topical agents remains controversial as well, and there is not sufficient evidence to indicate a prophylactic regimen using these agents for radiodermatitis.
Bolderston et al.  conducted a systematic review on the prevention and management of acute skin reactions related to radiation therapy. Unfortunately, the trials included in this systematic review were highly heterogeneous (the trials evaluated different kinds of treatments such as topical steroid creams, washing practices, sucralfate, Biafine cream, oral enzymes, amifostine, topical acid cream, aloe vera, chamomile cream, and dressings), and they concluded that there was insufficient evidence to support or refute specific topical or oral agents for the prevention or management of acute skin reactions .
Although various topical agents have been used to treat acute skin reactions, there is not sufficient evidence to establish a standardized recommendation for their application [3, 7]. In 2012, Zhang et al.  performed a meta-analysis on the use of topical agent therapy for the prevention and treatment of radiodermatitis. They concluded that topical agents could not prevent or treat radiodermatitis, probably because the topical agents chosen did not address the pathophysiology of radiodermatitis. An ideal agent for the prevention of radiodermatitis would mediate the repair of DNA damage or promote cell proliferation .
It was demonstrated that the cumulative effect of a low-power laser, when used at the appropriate dose, promoted tissue repair, possibly due to reduced inflammation and to the induction of collagen synthesis . Specifically, laser treatment had a positive effect on injured fibroblasts by directly stimulating their growth, by affecting the expression of genes related to cell migration, DNA repair, ion channels, membrane potential, and cellular metabolism. It is hypothesized that the sum of these events contribute to ulcer healing through an increase in collagen synthesis, microcirculation, and suppression of apoptosis .
The application of a low-power laser for the prevention of oral mucositis is already well-established [12–15]. Moreover, the application of laser treatments to patients with breast cancer has also been found to be safe , and this method currently represents an option for treatment of lymphedema, a side effect of the surgical treatment of breast cancer [17–20]. Furthermore, a meta-analysis demonstrated that there are no side effects due to use of a laser during these treatments .
Previously, only one study has investigated the use of photomodulation by using light emitting diodes (LEDs) . In this study, breast cancer patients were treated with radiation therapy following a lumpectomy, and LED photomodulation treatments were administered immediately following intensity-modulated radiation therapy (IMRT). These photomodulation treatments were found to reduce the incidence of skin reactions having a National Cancer Institute (NCI) grading of 1, 2, or 3 .
When laser therapy was applied to oral mucositis secondary to radiotherapy and chemotherapy, the incidence of grade 3 mucositis was reduced from 35.22 to 7.62% . Based on these results, it is hypothesized that laser treatments may also represent a prophylaxis for radiodermatitis, particularly since there is currently no effective treatment for this side effect of radiotherapy. Therefore, this randomized controlled trial was designed to assess the effectiveness of laser therapy for the prevention of radiodermatitis.