Photobiomodulation: A Systematic Review of the Oncologic Safety of Low-Level Light Therapy for Aesthetic Skin Rejuvenation

Executive summary

Concern that stimulating cell proliferation might also stimulate unwanted cell growth is the most reasonable safety question anyone asks about red light therapy. This review addresses it directly.

The author performed a focused systematic review in which safety data from clinical trials of photobiomodulation for skin rejuvenation was supplemented by analyses of in vitro data from cells derived from human skin and from human neoplastic cells, and in vivo data from tumours of the skin, oral cavity and breast.

The findings are reassuring but carefully bounded. Within established parameters, red and near-infrared light mainly enhanced proliferation of healthy cells without a clear pattern of influence on cell viability. The same light parameters mainly reduced neoplastic cell proliferation and viability, or else made no difference. Invasiveness potential, appraised by cell migration assays and differential gene expression, was equivocal. Photobiomodulation did not induce dysplastic change in healthy cells.

In vivo tumour models yielded varied results with no clear pattern emerging - stated plainly rather than glossed over.

Critically, there are no relevant clinical trial data linking photobiomodulation with any significant adverse events, including the finding of a new or recurrent malignancy. The author concludes that current evidence suggests photobiomodulation is oncologically safe for skin rejuvenation, and that there is no evidence supporting the proposition that it should be avoided by patients who have previously undergone treatment for cancer.

Why this research matters

Safety questions are the ones buyers most often ask and product marketing least often answers with evidence. This is a systematic review addressing one directly.

It is also relevant to a specific group of people who are frequently told, without evidence, that they should avoid light therapy: those with a history of cancer. This review found no evidence supporting that avoidance.

What the researchers found

Healthy cells. Within established parameters, red and near-infrared light mainly enhanced proliferation, without a clear pattern of influence on cell viability. Photobiomodulation did not induce dysplastic change in healthy cells.

Neoplastic cells. The same light parameters mainly reduced neoplastic cell proliferation and viability, or else made no difference.

Invasiveness potential. Appraised by cell migration assays and differential gene expression; results were equivocal.

In vivo tumour models. Varied results with no clear pattern emerging.

Clinical adverse events. No relevant clinical trial data linking photobiomodulation with any significant adverse events, including the finding of a new or recurrent malignancy.

No pooled effect estimates are generated and none are reproduced here.

What the results mean

The concern that red light might promote tumour growth is not supported by this evidence, and in cell studies the effect on neoplastic cells ran the other way or was neutral.

The honest qualifications are the equivocal invasiveness data and the varied in vivo results. Those are reported rather than buried, which increases confidence in the overall conclusion.

The clinical finding is the strongest element: across the trials reviewed, no significant adverse events including new or recurrent malignancy were linked to photobiomodulation. That is meaningful, while remembering that clinical trials of skin rejuvenation are typically short and not powered to detect rare long-term outcomes.

Strengths and limitations

Strengths

• Systematic methodology applied to a safety question.
• Combines clinical, in vitro and in vivo evidence layers rather than relying on one.
• Assesses multiple mechanisms of concern - proliferation, viability, invasiveness and dysplasia - not just one.
• Reports equivocal and varied findings plainly rather than emphasising only the reassuring results.
• Addresses a specific clinical question about patients previously treated for cancer.
• Published in a peer-reviewed surgical journal.

Limitations

• Confined to aesthetic skin rejuvenation applications.
• Specific light parameters, study counts and follow-up durations not reported in the source abstract.
• In vivo tumour model results were varied with no clear pattern.
• Invasiveness potential findings equivocal.
• Clinical trials in this field are generally short-term.
• Cannot rule out rare adverse events given the size of the clinical evidence base.

Evidence in context

This is the most methodologically rigorous safety assessment available in the field and its conclusions have not been challenged by later work as far as we are aware.

It complements rather than contradicts the same author's more sceptical 2021 review of efficacy evidence. The position across both is coherent: the safety case is reasonable, the efficacy case is unsettled, and the absence of regulatory standards is the main obstacle to resolving the second.

No large long-term cohort study of consumer photobiomodulation use exists, so long-term safety remains formally unestablished rather than doubted.

Related research

1. Photobiomodulation: a review of the molecular evidence for low level light therapy Glass GE. Journal of Plastic, Reconstructive & Aesthetic Surgery 74(5):1050-1060. 2021. PMID 33436333; doi:10.1016/j.bjps.2020.12.059.The same author's critical review of efficacy evidence and the regulatory standards gap.
2. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation Hamblin MR. AIMS Biophysics 4(3):337-361. 2017. PMID 28748217; PMC5523874; doi:10.3934/biophy.2017.3.337.The mechanistic account, including the biphasic dose response that defines 'established parameters'.
3. Photobiomodulation in human muscle tissue: an advantage in sports performance? Ferraresi C, Huang YY, Hamblin MR. Journal of Biophotonics 9(11-12):1273-1299. 2016. PMID 27874264; PMC5167494; doi:10.1002/jbio.201600176.Human muscle studies, a different exposure pattern not covered by this safety review.
4. General wellness: policy for low risk devices - guidance for industry and FDA staff U.S. FDA, Center for Devices and Radiological Health. Docket FDA-2014-N-1039. 2019. CDRH guidance.FDA guidance on where a general wellness product ends and a regulated medical device begins.