Photobiomodulation safety in cancer patients has been studied more extensively than most supportive care interventions in oncology. A retrospective analysis of 693 hematopoietic cell transplantation patients spanning a 15-year data collection window found no adverse effects associated with photobiomodulation therapy and no secondary malignancies in the oral cavity attributed to PBM. Two independent systematic reviews, one covering 67 studies across laboratory, animal, and clinical evidence, the other covering 27 human clinical studies focused specifically on tumor safety, both concluded that PBM is safe at currently recommended clinical parameters. This safety evidence is part of why the MASCC/ISOO issued formal recommendations for PBM use in cancer patients at their highest guideline level, a threshold that requires the evidence review committee to be satisfied on both efficacy and safety.
This article is part of our complete guide to Red and Blue Light Therapy for Oral Mucositis.
Key Takeaways
- Largest safety dataset shows no adverse effects: A 15-year retrospective study of 693 hematopoietic cell transplantation patients (the longest-duration, largest single-institution PBM safety dataset in oncology) found no adverse effects from photobiomodulation therapy and no secondary oral malignancies attributed to PBM.
- Two independent systematic reviews confirm safety: Bensadoun et al. (2020) reviewed 67 studies across laboratory, animal, and clinical evidence. De Pauli Paglioni et al. (2019) reviewed 27 human clinical studies focused on tumor safety. Both concluded PBM is safe at recommended clinical parameters, including in head and neck cancer in the area of PBM exposure.
- Safety conclusions carry a specific qualifier: “Safe at recommended clinical parameters” refers to the wavelengths, energy densities, and treatment durations used in the trials that informed the MASCC/ISOO guidelines.
The first question any oncologist asks about photobiomodulation is whether it could stimulate tumor growth. It's the right question, and it's the one the evidence has addressed most directly. Two independent reviews, one covering 67 studies, the other focused entirely on human clinical data, found no signal for tumor stimulation at the parameters used in clinical practice. A 15-year dataset of nearly 700 transplant patients found no secondary oral malignancies. That's not a theoretical reassurance; that's a clinical track record. The qualifier that matters is ‘at recommended parameters.’ That's where the evidence lives, and that's where the confidence applies. Outside those parameters, the data hasn't followed.— Dr. Sutherland, DDS
The 15-Year Retrospective Study
No adverse effects and no secondary oral malignancies attributed to photobiomodulation across 693 hematopoietic cell transplantation patients over a 15-year data collection window. That is the central finding from Bezinelli et al. (2021), published in Supportive Care in Cancer, conducted at Hospital Israelita Albert Einstein, one of the leading cancer treatment centers in Latin America.
Fifteen years is a meaningful follow-up window for evaluating delayed adverse effects, including any potential for secondary malignancy development. It is also a single-institution dataset, which means the consistency of protocols and monitoring is high but the population diversity is narrow. The finding carries real weight; the generalizability question is the one that prospective multi-center registries would answer.
Systematic Review Evidence on Tumor Safety
Two independent systematic reviews specifically investigated whether photobiomodulation poses a tumor safety risk, the most clinically urgent safety question for any intervention used in cancer patients.
Bensadoun et al. (2020), published in Cancer Medicine, reviewed 67 studies spanning in vitro (laboratory cell studies), in vivo (animal studies), and clinical (human patient) evidence. The review concluded that PBM is safe at currently recommended clinical parameters, including in head and neck cancer in the area of PBM exposure. That last point deserves emphasis: head and neck cancer patients receiving photobiomodulation for oral mucositis are applying light therapy directly to tissue in proximity to their tumor site, and the 67-study evidence base found no safety signal even in that scenario.
De Pauli Paglioni et al. (2019), published in Oral Oncology, took a narrower focus, reviewing 27 human clinical studies specifically examining PBM's safety profile in cancer patients. The review concluded that PBM use to prevent and treat cancer treatment complications is safe, while noting that further prospective studies with long-term follow-up are needed. That caveat is standard for the evidence tier; the retrospective and review data is consistently reassuring, and the call is for prospective confirmation of what the available data already shows rather than investigation of a detected risk.
What “Safe at Recommended Clinical Parameters” Means
The safety conclusions from both systematic reviews apply specifically to the clinical parameters studied in the trials that informed the MASCC/ISOO guidelines, not to all doses, all devices, and all application methods. The distinction is worth being precise about, because it gets blurred in most writing about PBM safety.
The studied parameters are typically red and near-infrared wavelengths in the 620–1000nm range, applied at specific energy densities and treatment durations. The safety data lives within those boundaries. Extrapolating safety to substantially different wavelengths, energy densities, or application durations beyond what the clinical evidence covers would exceed what the data supports.
This distinction matters practically for patients evaluating home-use devices, which may deliver different power outputs and energy densities than the clinical-grade lasers used in the trials. (For the evidence on LED devices specifically, see LED vs. Laser for Oral Mucositis.)
The Infection Complication Connection
Safety in the context of oral mucositis extends beyond the intervention itself to the condition it addresses. Oral mucositis introduces infectious risks that carry their own safety consequences, particularly in immunocompromised patients.
Eichhorn et al. (2025), in a systematic review and meta-analysis published in Cancers, confirmed that oral mucositis significantly elevates the risk of infectious complications following hematopoietic stem cell transplantation. The compromised mucosal barrier allows bacterial invasion into tissue and potentially into the bloodstream.
An intervention that reduces oral mucositis severity is therefore itself a safety intervention, reducing the window during which immunocompromised patients are exposed to a preventable infection pathway. The MASCC/ISOO recommendation for PBM as a preventive measure reflects this understanding, and it is one of the reasons the recommendation targets prevention rather than treatment alone.
What the Guideline Recommendation Implies About Safety
The MASCC/ISOO does not issue formal recommendations lightly, and the distinction between their recommendation levels is deliberate. A “recommendation” requires the evidence review committee to have high confidence that the benefits outweigh the harms. A “suggestion” reflects lower confidence or a less favorable benefit-harm balance.
PBM achieved recommendation-level status (not suggestion) across all three treatment settings: HSCT, head and neck radiotherapy, and head and neck chemoradiotherapy. The committee could not have reached this threshold without being satisfied that the safety evidence was adequate. The specific safety assessment methodology is internal to the MASCC/ISOO process and not publicly documented, which means the committee's reasoning is opaque even as the outcome is clear. What is visible is the result: highest-level recommendation for use in active cancer patients across three distinct treatment contexts, issued by the international expert body whose explicit mandate includes evaluating harm.
What Remains to Be Studied
The safety evidence is consistently reassuring across all available data. Three areas would strengthen it further.
Longer prospective follow-up. The Bezinelli retrospective provides 15 years of data, which is substantial. Prospective studies designed specifically to track long-term safety outcomes (10+ year follow-up from time of PBM exposure) would add a different kind of evidence. Retrospective data tells you what happened; prospective data tells you what to watch for. Both matter.
Diverse patient populations. The largest safety dataset comes from a single institution. Multi-center prospective safety registries across different patient populations, cancer types, and treatment regimens would broaden the generalizability of findings that are currently anchored to one hospital's patient cohort and protocols. This is the most consequential gap in the current evidence, because the safety question that remains open is not “is PBM dangerous?” (the data consistently says no) but “does the safety finding hold across populations the existing studies haven't reached?”
Device-specific safety data. The existing safety evidence comes primarily from professional-grade laser devices used in clinical settings. As LED-based devices enter the market for home use, device-specific safety data confirming that the safety profile established with clinical lasers extends to LED devices at their respective parameters would fill a gap that is becoming commercially relevant faster than the research is following.
This is a serious medical condition. Oral mucositis occurs in the context of cancer treatment. Patients should discuss any supportive care interventions, including photobiomodulation, with their oncology team before beginning use. (For the clinical evidence behind the MASCC/ISOO recommendation, see PBM for Oral Mucositis: Clinical Evidence and Guidelines. For the biological mechanisms, see How Red Light Therapy Works for Oral Mucositis.)
