Laser-assisted drug delivery: one trial could not show that adding the drug beats the laser alone

A 2021 trial in Acta Derm Venereol from Siriraj Hospital, Mahidol University, Thailand. Randomised, comparative, split-scar.

The paper states the problem plainly in its introduction — topical corticosteroid delivery following fractional laser treatment is an effective means of treating hypertrophic scars, but the relative efficacy of adjuvant corticosteroid treatment versus fractional laser monotherapy alone is unclear.

That is the question of this whole page. And here is how it was asked.

19 subjects' hypertrophic scars were split in half:

• one half — fractional laser + topical corticosteroid
• the other half — fractional laser + petrolatum

The results.

• at 3-month follow-up, a borderline significant reduction in scar thickness was observed in the laser+steroid group (p = 0.049)
• however, no significant long-term difference in scar flattening was observed between the two groups
• Patient and Observer Scar Assessment Scale scores showed significant improvement from baseline, without significant differences between the groups

Conclusion: fractional laser monotherapy is an effective treatment for hypertrophic scars, and the application of topical corticosteroid provides no long-term synergistic effect to fractional laser monotherapy.

Now how to read it.

First, 'borderline' is the paper's own word. p = 0.049. A value that barely stays under 0.05, and the paper itself called it borderline. This site does not delete that word and write only 'significant'. Putting 0.049 and 0.003 in the same sentence is the thing this site is trying to avoid.

Second, even that borderline difference appeared only in thickness at three months. In long-term flattening there was no difference, and on POSAS there was no difference either. One of three, and barely.

Third, the control is good. Not 'nothing' but laser + petrolatum. That is, both halves got the laser, and the only thing that differed was what went on top. A design like this is what it takes to see the drug's share. The absence of exactly this design is what this site regretted on the pycnogenol and N-acetyl glucosamine pages.

Fourth, and in that design almost no difference came out. That is the content of this entry.

Fifth, 19 people. Split-scar is a sensitive design, but this is small. Whether failing to find a difference means there is none, or that 19 could not catch it, cannot be separated from this trial alone. That p = 0.049 was the best of three endpoints is itself information, though.

Sixth, the authors declared no conflicts of interest. It is printed beneath the abstract. Where such a sentence exists, this site carries it across.

So it sits at 'moderate'. Own control with a good comparator, but 19 people and one trial.

A 2022 trial in Lasers Surg Med. Same team, same hospital as above. Randomised, split-scar, double-blinded.

This time the question is different — is it better to inject the corticosteroid, or to make channels and apply it?

Here the channels were made not by a laser but by a thermomechanical fractional injury (TMFI) device. The principle is the same — disrupting the skin barrier in a controlled manner to open a path for a drug.

21 subjects with hypertrophic scars on the abdomen took part, each scar split in half and treated five times.

• one half — TMFI + topical corticosteroid
• the other half — intralesional corticosteroid injection alone

The results.

• scar thickness, volume and Vancouver Scar Scale improved significantly from baseline in both segments
• at every follow-up visit there were no significant differences in mean scar thickness reduction between the two — except at 6 months, where the steroid injection segment's thickness reduction was significantly lower than the TMFI + steroid segment's (95% CI 0.09–0.35, p = 0.002)
• scar volume, Vancouver scores and patient self-assessment showed no significant differences at any visit
• pain — the injection segment was significantly more painful (95% CI −2.16 to −1.29, p < 0.001)
• adverse effects — skin atrophy, telangiectasia and post-inflammatory hyperpigmentation were noted in the injection segment, while none were observed in the TMFI + steroid segment

Conclusion: TMFI-assisted topical corticosteroid delivery is an effective treatment for hypertrophic scars with a lower risk of adverse effects than corticosteroid injection.

Now how to read it.

First, the firmest result here is not efficacy but adverse effects. Thickness, volume, scale and self-assessment were broadly no different; what clearly separated was pain (p < 0.001) and adverse effects. And those are exactly the known problems of intralesional corticosteroid injection — atrophy, telangiectasia, pigment change.

Second, 'no adverse effects were observed' is on 21 people. Not 'there are none', but none were visible in a trial this size.

Third, the direction of the 6-month thickness result needs care. The paper's sentence is that the injection segment's thickness reduction was significantly lower. So at that point TMFI + steroid was better. But at every other visit there was no difference, and there was no difference in volume, scale or self-assessment either.

Fourth, 21 people, on the abdomen. Results for the face or elsewhere cannot be taken from this trial.

Fifth, read it with the entry above. The same team asked two questions.

• 'Is adding a drug to the laser better?' → not in the long term
• 'What if you use channels instead of a needle?' → similar effect, less pain, fewer adverse effects

Put the two answers together and you can see where this technique is actually useful — not in making it work better, but in achieving about the same with less pain and less damage. That is worth something too, and it is a different story from the advertising.

Sixth, both trials came from the same institution. This is not independent replication. Whether the same result appears elsewhere we have not verified.

So this entry also sits at 'moderate'.