Low-level light therapy may speed up repair of radiation therapy-induced skin damage

Continuous exposure to radiation during cancer therapy promotes ulceration of tissues or radionecrosis, and a recent study revealed that the use of low-level light therapy may accelerate the resolution of skin damage by up to 50 percent.

Coined photobiomodulation, light therapy significantly reduced the incidence and severity of radionecrosis lesions, lessened inflammation, increased blood flow, and sped up wound healing by 19 days. [Photonics 2022;9:10]

On average, the lesions took 61 days to heal without photobiomodulation. But with therapy, healing occurred within 42 days using red light (660 nm) and 49 days using near-infrared light (880 nm). This indicates that treatments with red light were more effective at mitigating skin damage.

A team of researchers from the University at Buffalo, New York, US, completed the study in an animal model. They inserted radioisotope seeds (¹²⁵I seed, 0.42 mCi) subcutaneously on the backs of 36 athymic mice. To perform photobiomodulation treatment, the team used a LED device with a 1 cm² beam spot size with two wavelengths (660 nm and 880 nm). The device was applied directly in contact with the back of the mice over the site of seed insertion. Treatments were administrated once a week over 60 days.

“For over 40 years, photobiomodulation has been known to accelerate the healing of acute and chronic wounds, triggering cellular processes that control inflammation, pain signalling, and tissue regeneration and repair,” said lead study researcher Dr Rodrigo Mosca, a visiting fellow from the Nuclear and Energy Research Institute (IPEN) and the Federal University of Rio de Janeiro, both in Brazil.

The present data demonstrate the efficacy of photobiomodulation to effectively improve tissue resilience and healing to radiation damage, with the red wavelength being more beneficial than near-infrared for this specific application, according to Mosca.

Red and near-infrared lights have been shown to exert a direct modulatory effect on the mitochondrial enzymes, namely cytochrome C oxidase, resulting in processes that activate several signalling cascades that can induce increased cell growth rate, cell migration, apoptosis inhibition, and intense protein and nucleic acid synthesis. These, in turn, facilitate modulation of inflammatory processes, impaired pain signalling, and optimized tissue regeneration. [Adv Skin Wound Care 2019;32:157-167; IUBMB Life 2010;62:607-610; J Dent Res 2016;95:977-984]

Additionally, photobiomodulation can promote healing by activating TGF‐beta 1, a protein that controls cell growth and division, by stimulating various cells involved in healing, including fibroblasts (the main connective tissue cells of the body that play an important role in tissue repair) and macrophages (immune cells that lower inflammation, clean cell debris, and fight infection). [Sci Transl Med 2014;6:238ra69]

“To our knowledge, this is the first report on the successful use of photobiomodulation therapy for brachytherapy. The results … support future mechanistic lab studies and controlled human clinical studies to utilize this innovative therapy in managing side effects from radiation cancer treatments,” Mosca said.

The next step, according to the researcher, is to establish whether the effects of photobiomodulation extend to tumour cells. Several lines of evidence suggest that while exerting a modulatory effect on normal cellular responses, light therapy has an inhibitory response on tumour cells likely due to its inherently disturbed metabolic and regulatory signalling. [Photomed Laser Surg 2018;36:227-229]

“The ability [of photobiomodulation] to stimulate healing via cellular responses such as proliferation and migration has raised concerns on potential off-target effects on tumour cells… These responses need to be carefully investigated further in well-designed labs and clinical studies,” according to Mosca.