Dose-response and efficacy of 660-nanometer low-level laser therapy in healing diabetic foot ulcers: a randomized, double-blind, clinical trial.

Diabetic foot ulcers (DFU) negatively impact the quality of life and increase the risk of morbidity and mortality. Although photobiomodulation (PBM) produces better results in DFU healing than standard treatment or in the absence of irradiation, the ideal parameters are not standardized. This study aimed to evaluate the effect of PBM at a wavelength of 660 nm on reducing the DFU area. We compared the PBM treatment of non-infected DFUs. The sessions were held twice a week on non-consecutive days for 10 weeks (20 interventions) using HeNe 660 nm, 20 mW, in continuous mode, with three energy densities (4 J/cm², 8 J/cm², or 12 J/cm²). All patients underwent photobiomodulation therapy and conventional therapy (stereo gauze and Helianthus annuus vegetable oil), administered sequentially during the same treatment session. The control group was treated with GaAs at 904 nm, 70 mW, and an energy density of 10 J/cm² in continuous mode. The sessions were held twice a week on non-consecutive days for 10 weeks (20 sessions). The primary variable was the ulcer size reduction rate. There was no statistically significant difference in the ulcer reduction rate between the groups after 5 (p = 0.2582) and 10 weeks (p = 0.1164). Within each group, a significant reduction in ulcer size was observed over time (p < 0.0001). Regardless of the wavelength, all patients experienced a 50% reduction in the wound area when applying an energy density of 8-12 J/cm². However, the red group, which was treated at a lower energy density (4 J/cm²), had a lower proportion of responders. The application of PBM at a red wavelength of 660 nm at doses of 4, 8, and 12 J/cm², as well as the application of infrared light at 904 nm (10 J/cm²) significantly improved DFU healing after 10 weeks of treatment. Clinical Trial Registration: This study was registered at ClinicalTrials.gov, approved on July 9, 2022 (NCT05530486 || https://www.clinicaltrials.gov/ ).