Photobiomodulation and class 4 laser for peripheral neuropathy: what the evidence actually supports

Two published trials have tested laser photobiomodulation in people who already have peripheral neuropathy. Both were run in neuropathy caused by chemotherapy. One compared a very low-power laser against a sham device. At twelve weeks, the laser group’s response rate held while the control group’s fell.¹ The other used a class 4 laser. It reported improvement in nerve score and walking distance, and it had no control group at all.² Neither reports nerve regeneration, reversal, or a cure. Neither enrolled patients whose neuropathy comes from diabetes or metabolic disease.

That is a thin evidence base. The honest thing to do with thin evidence is not to shrink from it. It is to read it carefully: what each trial measured, who it let in, who it kept out, and what its design was never built to answer. That is what the rest of this page does.

The short version

• Two trials, two very different lasers. The only sham-controlled trial used a class 2M laser rated in milliwatts. The only trial that used a class 4 laser had no control group.
• Dose is the variable, not the word “laser”. Wavelength, power density, energy density and treated area differ hugely between the two trials. Light therapy also has a documented biphasic dose response: a low dose can help more than a high one.³
• Order of events matters. In the sham-controlled trial, the control arm responded slightly more often at six weeks. The two arms pulled apart only at twelve weeks. That raises a question about how long a course needs to be.¹
• Both trials studied cancer survivors. Neither enrolled diabetic, nutritional, autoimmune or idiopathic neuropathy.
• The registered diabetic neuropathy laser trials screened out the harder patients. They screened out peripheral vascular disease, open wounds on the treatment area, and recent diabetic ketoacidosis. One protocol also screened out anyone who had taken gabapentin, pregabalin, tramadol or an opioid in the previous month.^4,5
• Coverage is a payer decision, not a clinical finding. The 2006 Medicare determination that gets quoted here is about infrared diode pads. It is not about laser photobiomodulation.⁶
• Map the driver first. Which mechanism is active decides whether light-based therapy belongs in the plan at all.

Does class 4 laser therapy work for neuropathy?

When people ask whether class 4 laser helps neuropathy, they usually mean one thing. Does laser light improve neuropathy symptoms in humans? The evidence base is real, but it is small. And it does not carry over evenly across neuropathy types.

Neuropathy is a category, not a diagnosis

The same burning-feet complaint can come from many places. It can be metabolic injury, a vitamin deficiency, a toxic exposure, chemotherapy, an autoimmune process, or a structural cause. Those are different diseases that happen to share a symptom.

A trial run in one of those groups says very little about the others. That is not a criticism of the trials. It is a statement about how far a trial in one defined group can be stretched to cover others.

What is a class 4 laser?

Laser safety classes run from 1 up to 4. They describe how dangerous a beam is to the eye and skin. They are a regulatory hazard rating. They do not tell you the wavelength, the power density at the tissue, the energy delivered, or the area treated. Those are the things that decide what happens in the body.

This matters more here than usual. The two published trials sit at opposite ends of that scale. The one with a control arm is the one at the bottom.

Dose is the variable that separates these trials

Both trials are described as photobiomodulation. In the light they actually delivered, they have almost nothing in common.

The parameters that define a photobiomodulation dose

A photobiomodulation dose has many parts. It is defined by wavelength, power, power density at the tissue surface, energy density (fluence), and the size of the treated area. It also depends on whether the beam is continuous or pulsed, how long each session lasts, and how many sessions are given over what period. Change any one of those, and you have changed the treatment.

The sham-controlled trial used a class 2M continuous-wave diode laser. It delivered 8 milliwatts through a 3.2 millimeter aperture (opening), applied point by point. There were sixteen points in the interdigital spaces (the gaps between fingers and toes) of the hands and feet. There were ten more points over the skin landmarks for the C6–T1 and L5–S1 nerve roots on both sides. The dose was 1 joule per point, rising to 2 joules per point in later sessions as tolerated. Treatment ran twice a week for six weeks.¹

The class 4 trial used a device that combined two diodes at 905 nanometers and 808 nanometers. One was pulsed and one was continuous. Peak powers were 25 watts and 1.1 watts. The power density was 0.168 watts per square centimeter. The beam spot was 150 square centimeters, covering the plantar surfaces of the hands and feet on both sides. The dose was set as an energy density of 6 or 8 joules per square centimeter. Treatment ran twice weekly for three weeks.²

Notice that the two doses are not even reported in the same units. One is joules per point at twenty-six separate points. The other is joules per square centimeter across a large field. There is no clean way to convert one into the other. That means the two trials cannot be pooled, compared, or averaged in any meaningful way.

The biphasic dose response

This is not a bookkeeping problem. It is the main reason results in this field disagree.

A 2009 review in the journal Dose-Response came from the Wellman Center for Photomedicine at Massachusetts General Hospital. It described a biphasic dose response seen again and again in low-level light therapy. Low levels of light stimulate and repair tissue better than higher levels do. The authors describe this pattern using the Arndt-Schulz curve.³ More is not better, and past a point more is worse.

The same review makes a point that bears directly on this page. Light therapy has many settings: wavelength, fluence, power density, pulse structure and treatment timing. Choosing among them rationally is hard. That difficulty has produced a body of research with both negative and positive studies.³ So a negative photobiomodulation trial can mean the therapy does not work. Or it can mean that particular dose did not work. From outside the trial, those two look identical.

So when you see mixed results in light therapy, do not conclude the field is unserious. Ask what dose was tested, in whom, and for how long.

The sham-controlled trial: 44 cancer survivors, 2022

This is the only randomized, sham-controlled trial of photobiomodulation in established neuropathy discussed here. It deserves a close reading, not selective quoting.

Who was studied

Teng and colleagues published in Supportive Care in Cancer. They enrolled 44 cancer survivors who still had neuropathy symptoms. Each was at least three months past finishing potentially neurotoxic chemotherapy (chemotherapy that can damage nerves). Participants were randomized 2:1, with 29 to laser and 15 to sham. They were treated twice weekly for twelve sessions over six weeks. Assessments came at baseline, six weeks and twelve weeks.¹

The group was 61 percent female, with a mean age of about 62. Just under half had colorectal cancer, and about a third had breast cancer. On average, roughly fifteen months had passed since chemotherapy. Neuropathy was grade 1 in 64 percent and grade 2 in 36 percent. That is mild to moderate.¹

Who was screened out

The trial listed six specific exclusions. They are worth reading as a description of who was not in the room.¹

• Anyone unable to lie flat on their back (supine) for a thirty-minute period.
• Anyone with an open wound or ulcer over the treatment area.
• Anyone with a clinical diagnosis of peripheral neuropathy from another cause. The paper notes that diabetes without neuropathy was not itself an exclusion. But diabetes with neuropathy was, because that is a second cause.
• Anyone with uncontrolled psychiatric illness or cognitive dysfunction (problems with thinking or memory) that could get in the way of completing assessments.
• Anyone with a life expectancy under three months.
• Anyone using a concurrent complementary therapy for neuropathy during the study.

Read together, this describes a fairly well, fairly mobile group. They had one identified cause of neuropathy, intact skin on the feet, no other treatments running alongside, and mild to moderate severity. That is a clean trial population. It is not the population that walks into a neuropathy clinic. That patient has type 2 diabetes, an old foot ulcer, three prescriptions for nerve pain and fifteen years of symptoms.

What the response rates showed, and in what order

At six weeks, response rates were 48 percent in the laser group and 53 percent in the sham group. At twelve weeks, they were 45 percent and 33 percent, in the same order.¹ In plain terms, the sham group responded slightly more often at the end of treatment. The two arms pulled apart only at follow-up. The laser group held its gains, and the control group’s declined.

That finding must stay on the page. It also has to be read with three facts attached.

First, this was a non-comparative trial by design. Each arm was tested against a fixed statistical threshold. It was not tested against the other arm. The published null hypothesis was that the true response rate is 5 percent. The sample size was set to give 80 percent power if the true response rate on treatment were 20 percent.¹ The authors state plainly that the design did not allow a statistical comparison between the treatment and control arms.

Second, the control arm had fifteen people in it. In an arm of fifteen, one person is worth about seven percentage points. So the five-point gap at six weeks is smaller than a single person’s response.

Third, the laser arm’s response rate did beat the trial’s preset threshold at both time points. Reported side effects were low grade.¹ The authors’ own conclusion is measured. They say the result warrants evaluation in a properly powered phase III trial.

Why a sham arm is hard to build in a light-therapy trial

The paper describes its sham honestly. Sham patients got the same visit schedule and the same eye mask. They got the same equipment and the same application points. An opaque aluminum cover blocked the laser aperture. That way the sensory experience would match the active treatment.¹ That is a careful design. And with a device delivering 8 milliwatts, there is little heat or sensation to give the difference away.

Blinding was still incomplete, and the authors say so. The trial was single-blinded. The physician investigator who did the clinical neuropathy assessment was unblinded. The paper’s own list of limitations names the unblinded clinical assessor and therapist as a weakness.¹ An unblinded assessor knows which group a patient is in. That can shift a clinician-rated score in either direction.

None of this is a reason to discount the trial. It is a reason to hold both arms’ numbers loosely, including the six-week ones.

What this design could not capture

The authors list the limitations themselves. The sample was small, and the treatment period was short. The assessor and therapist were unblinded. COVID-19 restrictions caused unavoidable delays to study visits. The authors also note that no neurophysiological testing (nerve testing) was done because of limited resources. They suggest it as an objective measure for a future trial.¹

Three more things follow from the design, not from any fault in it. First, the trial tested laser alone. So it cannot say anything about laser used alongside metabolic correction, nutritional repletion (restoring missing nutrients) or exercise. Second, follow-up stopped at twelve weeks, which is six weeks after the last session. Nothing in it speaks to how long results last beyond that. Third, there was no nerve conduction testing. So the trial measured symptoms and function, not the nerve itself.

The NEUROLIGHT pilot trial: 60 patients, a class 4 laser, 2026

The second trial is the one that actually used a class 4 device. It is a pilot (a small early study) without a control group.

Who was studied

Claes and colleagues published in Lasers in Medical Science. They treated 60 cancer patients with chemotherapy-induced peripheral neuropathy. The work took place at Jessa Hospital in Hasselt, Belgium, between February 2022 and November 2023. Twenty-eight received six sessions at 6 joules per square centimeter. And thirty-two received six sessions at 8 joules per square centimeter. Both groups were treated twice weekly over three weeks.²

Most participants were women, with mean ages around 61 to 64. Breast cancer was the most common primary cancer. Next came colorectal, head and neck, ovarian, endometrial, bladder, lung and prostate.²

Who was screened out

The entry rules were narrower than they first appear. A patient needed a physician diagnosis of chemotherapy-induced neuropathy. They had to be at least 18. They had to have had one of a specific list of neurotoxic agents: paclitaxel, docetaxel, oxaliplatin, cisplatin, thalidomide, bortezomib or vincristine. The last dose had to be at least two weeks earlier. And they needed a Fitzpatrick skin type between I and V.²

That last rule excluded Fitzpatrick type VI, the most deeply pigmented skin. Pigment absorbs light. So this is a real limit on who the reported doses have been tested in.

The stated exclusions were two. One was skipping more than two treatment sessions in a row. The other was having neuropathy symptoms before receiving chemotherapy.² That second one is the important one. It removes exactly one kind of patient. That patient arrives at a neuropathy clinic with pre-existing diabetic or idiopathic (no known cause) neuropathy that chemotherapy then made worse. That is a common and difficult case, and this trial cannot speak to it.

What moved and what did not

The modified Total Neuropathy Score improved significantly over time (P = 0.048). So did the six-minute walk test (P < 0.001). Walking distance improved about 13 percent in the lower-dose group and about 18 percent in the higher-dose group. Pain scores on the numeric rating scale improved over time (P < 0.001), with better scores in the lower-dose group (P = 0.034). Patient satisfaction improved (P = 0.003). No adverse events were reported.²

Not everything moved. There was no significant change in the FACT/GOG-NTX total score or in its neurotoxicity subscale. That means the broader quality-of-life questionnaire did not pick up the same signal.²

That split between a walking test and a questionnaire is common in neuropathy research. It is a practical reason to track what you can do, such as how far you can walk and how steady you are. One overall score is not enough.

Note also that the lower dose, not the higher one, produced the better pain scores. On that basis, the authors decline to name an optimal fluence.² That is the biphasic dose response showing up inside a single trial.

What this design could not capture

The central limitation is built into the design. Both groups received photobiomodulation, and there was no sham arm. So improvement over time cannot be separated from natural recovery. Nor can it be separated from regression to the mean (extreme scores drifting back toward average) or from a placebo effect. The authors say this plainly. They accept that a placebo effect could partly explain the results.²

The authors also report that the sample was too small to sort results by key factors. These included chemotherapy type, number of cycles, and time since chemotherapy ended. They also included prior lines of neurotoxic treatment and neuropathy-inducing comorbidities (other conditions) such as diabetes. The effect of other drugs taken at the same time, like duloxetine and pregabalin, was not assessed.² In other words, the trial could not tell you whether a diabetic patient in the group did better or worse than a non-diabetic one.

Twenty of the sixty patients were lost to follow-up, twelve in the lower-dose group and eight in the higher-dose group.² That is a third of the sample. It is one more reason to read the later time points with caution.

How long does a course need to be?

The timeline in the sham-controlled trial is the most useful thing on this page. The laser arm did not lead at six weeks. It led at twelve.¹

Two readings are possible, and the trial cannot tell them apart. Either the laser effect takes longer to appear than a treatment course lasts. Or the control group’s early response was a short-lived placebo response that faded on schedule, while the laser group’s did not. Both fit the numbers.

Either way, the practical lesson is the same. Judging a course of photobiomodulation the moment the last session ends is judging it too early. It also makes follow-up length a fair question to ask of any trial in this field. The sham-controlled trial stopped at twelve weeks. The class 4 pilot collected data at baseline, after the six sessions, three weeks later, and again at six months and one year. But with no control arm, its long-term numbers cannot be credited to the laser.^1,2

Does laser therapy work for diabetic neuropathy?

Diabetic peripheral neuropathy is the clearest gap in this evidence. Neither trial above enrolled that population. The mechanisms also differ. Metabolic and microvascular injury (damage to the tiny blood vessels) varies from patient to patient. A single fixed protocol is unlikely to address that evenly. Several of those drivers are covered in our review of the hidden drivers behind peripheral neuropathy.

Two registered sham-controlled trials, and what they excluded

Laser trials in diabetic neuropathy have been registered and run. Two sham-controlled trials of the same device were registered on ClinicalTrials.gov. The device was a 635-nanometer, three-diode, 17-milliwatt laser. Both trials applied it fifteen minutes per foot, twice weekly for six weeks.^4,5

The first was completed with 30 participants.⁴ The second was terminated after enrolling 18, because it could not recruit. Summary results are posted on its registry record.⁵ Neither is a peer-reviewed publication, and neither is large enough to settle anything. What they do record precisely is who was allowed in.

Both protocols required foot pain that was chronic, bilateral (in both feet), and roughly the same on each side. The pain had to be rated at least 50 on a 0–100 visual analog scale. Patients also had to be on a stable diabetes medication plan for the preceding 30 days.^4,5

The exclusions are the striking part. Across the two records, people were excluded for any of the following:^4,5

• Foot pain that was unilateral or noticeably different between the two feet.
• Pain rated below 50 on the visual analog scale — that is, milder cases.
• Foot pain not clearly linked to diabetes, or linked to diabetes plus something else.
• Serious organ disease or other serious primary disease.
• Diabetic ketosis, ketoacidosis or severe infection within the previous two weeks.
• An active chronic pain condition. The second record names chronic fatigue syndrome, fibromyalgia, endometriosis, inflammatory bowel disease, interstitial cystitis and peripheral vascular disease.
• Cancer, or treatment for cancer, in the previous six months.
• An active infection, wound or other external trauma anywhere on the treatment area.
• Previous surgery or an implanted device for diabetic neuropathy foot pain.
• Analgesics or NSAIDs within seven days. Antidepressants within 30 days. Gabapentin, pregabalin, tramadol or opioid medicines within 30 days. Local anesthetic injections within 30 days.
• Ongoing litigation or disability benefits related to the study parameters.

Why that matters for a patient with metabolic disease

Line those rules up against a real clinic waiting room. A patient with peripheral vascular disease is out. A patient with a healing ulcer is out. A patient whose neuropathy is part metabolic and part something else is out. A patient with fibromyalgia alongside their neuropathy is out. A patient on gabapentin or pregabalin is out unless they stop for a month. That is a large share of people who have been treated for painful neuropathy. A patient whose pain is bad in one foot and mild in the other is out.

This is not sharp practice by the investigators. Trials are built this way on purpose, to cut noise and isolate a single effect. But it has a consequence that gets skipped over all the time. A modest or null result in such a tightly selected group does not establish that the treatment fails in the patients who were screened out. It establishes what happened in the patients who were let in.

The patients screened out here had vascular disease, unstable glycemic control (blood sugar control) or open wounds. Others had several pain conditions, polypharmacy (many medicines at once) or mixed causes. They are exactly the patients a metabolic neuropathy practice sees most days. The evidence is truly silent about them. Silence is not a negative finding. It is not a positive one either.

Does Medicare cover laser treatment for neuropathy?

A national coverage determination in effect since October 24, 2006 states that infrared therapy devices are not covered by Medicare for treating diabetic or non-diabetic peripheral sensory neuropathy, or wounds or ulcers of the skin and subcutaneous tissues, including for pain arising from those conditions.^6,7

The determination is specific about what it is describing. It defines an infrared therapy device as an array of juxtaposed infrared diodes affixed to a flexible pad held in contact with the skin, which can also produce local warming as a secondary effect.⁶ That is a different piece of equipment from a laser, and the determination was written about the evidence for those pad devices.

It is a payer decision about a device category. It is not a clinical conclusion about laser photobiomodulation. It should not be read as either an endorsement or a verdict. Because it dates from 2006, it also predates both trials on this page. Local coverage rules may differ. Nothing here is a benefits determination for any individual.

Where a service is not covered, patients sign an Advance Beneficiary Notice before it is provided. That way the financial side is settled in writing in advance, not discovered afterward. It is fair to ask any clinic which device it is using. It is also fair to ask which coverage language it is relying on.

How light-based therapy fits into an evaluation-first plan

Class 4 photobiomodulation, class 3B cold laser, and whole-body infrared are offered here. They are part of a plan built around whichever driver the evaluation identifies. They are not offered as nerve regeneration or reversal, and no success rate is published for them.

Before any of it is discussed, the evaluation looks for which mechanism is active. Electrodiagnostic testing (EMG/NCS) is performed on site. VNG (videonystagmography) is also available. It is a diagnostic test of inner-ear balance function, used when dizziness or unsteadiness is part of the picture. It is a test, never a treatment.

The published trials tested light on its own. That is the only way to isolate its effect, but it is not how neuropathy is usually treated. Here, light-based therapy sits alongside metabolic and nutritional care aimed at the driver itself. That combination has not been tested in a randomized trial. Saying so is more useful than implying it has.

Orthobiologic injections (PRP and BMAC) are offered here as well.

What all of this adds up to is a conversation, not a protocol. The risks of photobiomodulation reported in these trials were low: mild, low-grade events in one and none in the other. The potential benefit in a patient like you is truly uncertain. Both halves of that picture belong in the discussion before anyone starts a course of treatment.

What to ask before you commit to a course of treatment

• Which neuropathy driver do you believe is dominant in my case, and what did you base that on?
• Is the plan supported by trial evidence in a population like mine, or extrapolated from a different one?
• If it is extrapolated, what specifically about my case makes you think it transfers?
• How many sessions, over what period, at what wavelength and what energy density?
• When will we judge whether it is working, and why then rather than at the last session?
• What function will we measure, not just what pain score?
• Which device is this, what class is it, and what coverage language applies to it?

Where we are and how to start

Regenerve is located at 4477 Woodson Rd #104, St. Louis, MO 63134, minutes from St. Louis Lambert International Airport, and we see patients from across the St. Louis region, Missouri and Illinois. You can call (314) 886-5739 or text (314) 886-5902, or email info@regenerve.com.

The free Nerve Damage Score is a five-question starting point for the driver question. That is the question that decides whether light-based therapy belongs in your plan at all.

Both laser trials enrolled people treated with chemotherapy. So chemotherapy-induced peripheral neuropathy (CIPN) is the closest match to their results. The injection-based option in the same plan is covered in orthobiologic injections for peripheral neuropathy.

Frequently asked questions

Is the evidence for photobiomodulation in neuropathy strong enough to rely on?

On its own, no. There are two published trials in established neuropathy, both in chemotherapy-induced cases. One is small and sham-controlled, and one has no control group at all.^1,2 That is a reason to treat it as one part of a plan aimed at an identified driver, not as the plan. It is not a reason to call it disproven, because the trials that exist have not studied most of the people asking the question. See the treatments offered here.

Does that evidence transfer to diabetic neuropathy?

Not automatically. Diabetic peripheral neuropathy involves metabolic and microvascular (small blood vessel) drivers. These vary between patients. Neither published trial on this page enrolled that population. Registered diabetic neuropathy laser trials do exist. But they excluded peripheral vascular disease, open wounds on the feet, and recent ketoacidosis. They also excluded patients taking common nerve pain medications. So they say little about a complex metabolic patient either.^4,5 See how diabetic peripheral neuropathy is approached here.

The sham group did better at six weeks. Does that mean the laser did nothing?

It means the trial did not show a laser advantage at the end of treatment, which is worth knowing. It does not mean nothing happened, for three reasons. First, the trial was designed as non-comparative, and its authors state it could not statistically compare the arms. Second, the control arm had only fifteen people, so a five-point gap is smaller than one participant’s response. Third, by twelve weeks the laser group had held its response while the control group’s had fallen.¹ See which specialist to see when neuropathy has not improved.

How is photobiomodulation different from Qutenza?

They are unrelated mechanisms with very different evidence. Qutenza (capsaicin 8% patch) is FDA-approved in adults only for neuropathic pain from postherpetic neuralgia and from diabetic peripheral neuropathy of the feet. It is applied in clinic by a clinician, never dispensed for home use, and repeated no more often than every three months. See how Qutenza is used in clinic.

Will Medicare cover light therapy for neuropathy?

A national coverage determination in effect since October 2006 makes infrared therapy devices non-covered for peripheral sensory neuropathy, wounds and ulcers.⁶ That determination describes arrays of infrared diodes on a flexible pad. It does not describe laser photobiomodulation. And coverage is a payer decision, not a statement about whether something works. Where a service is not covered, an Advance Beneficiary Notice is signed before treatment. Contact us with coverage questions.

Can laser therapy reverse neuropathy?

No published trial shows that. Neither of the two trials in established neuropathy reports nerve regeneration, reversal or a cure. That is why light-based therapy is not offered here as nerve regeneration or reversal. No success rate is published for it. It is used alongside metabolic and nutritional care aimed at whatever driver the evaluation finds.

What are the side effects of class 4 laser therapy?

In the published trials, very few. The class 4 pilot trial in 60 patients reported no adverse events, and the sham-controlled trial reported only mild, low-grade side effects. One limit matters: the class 4 trial excluded the most deeply pigmented skin, Fitzpatrick type VI. Pigment absorbs light, so the reported doses have not been tested in that skin type.

How many laser sessions does neuropathy treatment take?

The two trials used different schedules: twelve sessions over six weeks with a low-power laser, and six sessions over three weeks with a class 4 laser. In the sham-controlled trial, the laser group did not pull ahead until twelve weeks, six weeks after the last session. So a course should not be judged the day it ends. Ask when progress will be measured, and why then.

What are the drawbacks of laser therapy for neuropathy?

The main drawback is a thin evidence base. Only two trials have tested it in established neuropathy, both in people whose nerve damage came from chemotherapy. The class 4 trial had no control group and lost a third of its patients to follow-up. Neither trial enrolled diabetic neuropathy. Medicare does not cover infrared pad devices for neuropathy, though that rule was not written about lasers.

Sources

1. Teng C, Egger S, Blinman PL, Vardy JL. Evaluating laser photobiomodulation for chemotherapy-induced peripheral neuropathy: a randomised phase II trial. Supportive Care in Cancer. 2022;31(1):52. https://pmc.ncbi.nlm.nih.gov/articles/PMC9758032/ (44 cancer survivors at least 3 months after neurotoxic chemotherapy; randomized 2:1, 29 laser and 15 sham; class 2M continuous diode laser, 8 mW through a 3.2 mm aperture, 1–2 J per point at 26 points, twice weekly for 12 sessions; response rates 48% laser and 53% sham at 6 weeks, 45% and 33% at 12 weeks; non-comparative design; null hypothesis of a 5% true response rate; sham delivered with the aperture occluded by an opaque aluminum cover; limitations include small sample, short intervention period and unblinded clinical assessor and therapist).
2. Claes M, Lodewijckx J, Robijns J, Hermans S, Peeters P, Mebis J. Evaluating the efficacy of photobiomodulation therapy in the management of chemotherapy-induced peripheral neuropathy: a pilot trial (NEUROLIGHT trial). Lasers in Medical Science. 2026;41(1):57. https://pmc.ncbi.nlm.nih.gov/articles/PMC12988979/ (60 cancer patients with chemotherapy-induced peripheral neuropathy at Jessa Hospital, Hasselt, Belgium, February 2022 to November 2023; class IV MLS M6 laser, 905 nm and 808 nm, peak power 25 W and 1.1 W, power density 0.168 W/cm², 150 cm² beam spot; 6 sessions at 6 J/cm² (n = 28) or 8 J/cm² (n = 32); Fitzpatrick skin types I–V only; exclusions were interruption of more than two consecutive treatments and neuropathy symptoms preceding chemotherapy; mTNS P = 0.048, 6MWT P < 0.001, NRS pain P < 0.001 favoring the 6 J/cm² group P = 0.034, no significant difference in FACT/GOG-NTX total score or neurotoxicity subscale; no control group; 20 of 60 lost to follow-up).
3. Huang YY, Chen AC, Carroll JD, Hamblin MR. Biphasic dose response in low level light therapy. Dose-Response. 2009;7(4):358–383. https://pmc.ncbi.nlm.nih.gov/articles/PMC2790317/ (low levels of light stimulate and repair tissue more effectively than higher levels, described by the Arndt-Schulz curve; the difficulty of choosing among wavelength, fluence, power density, pulse structure and treatment timing has produced both negative and positive studies).
4. ClinicalTrials.gov. Study of Low Level Laser Therapy to Treat Diabetic Peripheral Neuropathy Foot Pain (NCT02461225). Erchonia Corporation. https://clinicaltrials.gov/study/NCT02461225 (double-blind, placebo-controlled randomized evaluation of the Erchonia FX-635; completed with 30 participants; three 17 mW 635 nm diodes, 15 minutes per foot, twice weekly for 6 weeks; full inclusion and exclusion criteria as summarized above).
5. ClinicalTrials.gov. An Evaluation of the Effect of Low Level Laser Therapy on Diabetic Peripheral Neuropathy Pain (NCT04006392). Erchonia Corporation. https://clinicaltrials.gov/study/NCT04006392 (double-blind, placebo-controlled randomized evaluation of the Erchonia FX-635; terminated for inability to recruit after enrolling 18 participants; results posted March 14, 2023; exclusions include peripheral vascular disease, active infection or wound on the treatment area, serious organ disease, and recent diabetic ketosis or ketoacidosis).
6. Centers for Medicare & Medicaid Services. National Coverage Determination 270.6: Infrared Therapy Devices. Effective October 24, 2006. https://www.cms.gov/medicare-coverage-database/view/ncd.aspx?ncdid=315&ncdver=1 (infrared and near-infrared light and heat, including monochromatic infrared energy, non-covered for diabetic and non-diabetic peripheral sensory neuropathy, wounds and ulcers of the skin and subcutaneous tissues, including pain arising from those conditions; the determination describes an array of juxtaposed infrared diodes affixed to a flexible pad held against the skin).
7. Centers for Medicare & Medicaid Services. Decision Memo for Infrared Therapy Devices (CAG-00291N). 2006. https://www.cms.gov/medicare-coverage-database/view/ncacal-decision-memo.aspx?proposed=N&ncaid=176 (the national coverage analysis underlying NCD 270.6).