Whether Red Light Therapy (RLT), also known as photobiomodulation (PBM), is safe for breast cancer patients is a common and important concern during treatment and survivorship. RLT is a non-invasive treatment using specific wavelengths of light, typically in the red (600-700 nanometers) and near-infrared (700-1000 nm) spectrums, to interact with tissues. The primary worry is that this light-based therapy, known to promote cellular activity, could inadvertently stimulate the growth of residual cancer cells or metastases. Examining RLT’s scientific mechanisms and its application in oncology is necessary.
Understanding Red Light Therapy’s Mechanism
The scientific basis of RLT, or photobiomodulation, involves non-ionizing light energy being absorbed by molecules within the cell. The primary target is the enzyme cytochrome c oxidase, located in the mitochondria, the cell’s powerhouse. When photons from the red and near-infrared spectrum reach this enzyme, they trigger a cascade of biochemical events. This interaction increases the production of adenosine triphosphate (ATP), the cell’s main energy currency.
The resulting boost in cellular energy reduces oxidative stress and promotes cellular repair and regeneration. Wavelengths between 630 and 970 nm are effective because they penetrate tissues to reach the mitochondria. Red light (630–670 nm) is used for superficial tissues, while near-infrared light (780–850 nm) penetrates more deeply to affect nerves and deeper structures. This cellular stimulation forms the basis for RLT’s therapeutic effects, such as reducing inflammation and pain in non-cancerous tissues.
The Primary Safety Concern: Tumor Stimulation
The main theoretical concern is that RLT’s cell-stimulating effects could promote the proliferation of remaining cancer cells. This idea originates from in vitro studies showing that photobiomodulation can stimulate cell division and growth under certain parameters. However, the tumor microenvironment in a living organism is far more complex than a cell culture.
Clinical and preclinical evidence suggests that RLT, when used appropriately, is oncologically safe and does not appear to increase the risk of recurrence or new malignancy. Some in vitro studies on breast cancer cells have even shown that specific red light wavelengths, like 660 nm, can possess anti-proliferative effects by inducing cell death pathways. Furthermore, a systematic review of 67 studies found no evidence that PBM increases cancer risk.
The precise dose and wavelength of the light are key factors, as different parameters produce different biological outcomes. Experts agree that RLT operates at wavelengths that lack the energy to directly damage DNA, unlike ultraviolet (UV) radiation, making the development of new cancers highly unlikely.
Applications for Managing Treatment Side Effects
While direct application of RLT over a tumor site requires caution, the therapy is useful for managing debilitating side effects of breast cancer treatment. RLT is recognized as a supportive therapy to improve a patient’s quality of life during and after oncology care.
Chemotherapy-Induced Peripheral Neuropathy (CIPN)
One major application is the mitigation of CIPN, a condition causing pain, numbness, and tingling in the hands and feet. RLT’s ability to enhance circulation, reduce inflammation, and stimulate the repair and regeneration of peripheral nerves positions it as a promising non-pharmacological option. Studies have shown that both red and near-infrared light can lead to significant improvements in functional recovery and mobility for patients experiencing this chronic side effect.
Oral Mucositis and Dermatitis
RLT is widely used to prevent and treat oral mucositis, painful sores in the mouth and throat caused by chemotherapy or radiation. PBM is effective, particularly as a preventive measure, by reducing inflammation and accelerating tissue healing in the oral mucosa. Additionally, RLT helps manage radiation-induced skin reactions, or dermatitis, a common occurrence following radiation therapy. The light therapy interrupts the inflammatory process, reduces pain, and promotes faster healing of skin tissues.
Lymphedema Management
Another important application is in the management of lymphedema, a chronic swelling often resulting from lymph node removal or damage during treatment. RLT, particularly with near-infrared wavelengths (810-850 nm), stimulates lymphatic drainage and helps soften hardened, fibrotic tissue. This can lead to a reduction in the volume and circumference of the affected limb and a decrease in pain. The mechanism involves supporting the formation of new lymphatic vessels, which helps to restore proper fluid flow.
Professional Guidance and Clinical Context
Given the complexity of cancer, RLT is considered an adjunctive therapy and should never replace standard oncology care. The timing and location of the application are paramount to its safety and effectiveness. Practitioners advise avoiding direct application of RLT over the primary tumor site or metastatic lesions during active treatment, unless specifically directed by the oncologist.
RLT is generally viewed more favorably in the survivorship phase or when treating side effects distant from the original tumor site. Patients must have an open conversation with their entire oncology team before starting any RLT regimen. This consultation ensures that RLT parameters, such as wavelength and dose, do not interfere with the efficacy of systemic treatments or radiation fields. Integrating PBM into the comprehensive care plan allows patients to safely benefit from its regenerative properties for symptom management.