Monday, June 1, 2015

Ablative CO2 Fractional Photothermolysis for Burn Scars

Hypertrophic scarring after burn injury presents a clinical challenge. In addition to persistent cosmetic concerns, such scarring can also cause pain, tightness, restricted motion and severe itch. Although the field has seen few advances in the treatment of such scars in the past decade, recent studies have indicated that pulsed dye laser and fractional CO2 laser treatment lead to improvements in abnormal pigmentation, pruritus, pain and tightness (1). A fractional CO2 laser that has been in use at Massachusetts General Hospital since 2011 has shown great promise as a therapy that improves appearance of burn scars and can help address other symptoms.

Burn surgeons at Mass General’s Sumner M. Redstone Burn Center, led by plastic surgeon Jeremy Goverman, MD, FACS, and colleagues, undertook a study to evaluate the effects of ablative CO2 fractional photothermolysis on burn scars. The results, which have yet to be published, showed significant improvements in patient symptoms, enhanced cosmetic appearance of the burn scars and a high level of post-treatment patient satisfaction.

Mechanisms of Action in Laser Treatment of Hypertrophic Scars

The fractional CO2 laser used by Mass General burn surgeons creates small holes in the scar tissue using a finely focused beam of light. This technique, which can penetrate to the base of the scar, selectively ablates only thin columns of tissue, called microthermal zones, limiting damage to the surrounding tissue.

There are several mechanisms through which CO2 fractional photothermolysis is hypothesized to act. First, the laser creates organized columns of microthermal injury, which break down the collagen in those columns, stimulating the process of collagen remodeling and promoting the formation of more elastic tissue. The microscopic holes could also release dermal tension, which is responsible for the tightness and raised nature of hypertrophic scars. Finally, the small columns surrounded by normal tissue might create microscopic healing zones, where the heat from the ablation induces a metabolic cascade that recruits stem cells from the bloodstream to aid in repair at the scar site.

Superficial and Deep Fractional Resurfacing
Superficial and Deep Fractional Resurfacing
Two laser handpieces are used for treatment: the superficial fractional handpiece and the deep Fx handpiece. The superficial handpiece helps to smooth surface abnormalities by ablating a thin layer of skin (left). The deep Fx handpiece is used to perform fractional photothermolysis (FP) by creating columns of thermal damage (referred to as microthermal zones) in the epidermis and dermis surrounded by islands of normal tissue (right). The tissue injury created with FP stimulates the process of collagen remodeling and deposition and promotes elastic tissue formation.
Source: Jeremy Goverman, MD

Assessing Efficacy of Laser Treatment

Although preliminary data seen with ablative fractional CO2 laser treatment of hypertrophic burn scars (2) has been positive, there is a need for more robust evidence to validate its use. Dr. Goverman and his team sought to quantify and assess patient-reported outcomes among those treated with fractional CO2 laser at Mass General’s Sumner M. Redstone Burn Center. Assessing the effects of a treatment on burn scars can present methodological challenges, as it requires objective measurements of changes on scar tissue, which is highly heterogeneous. The research team instead measured success in patient-reported outcomes.

Before vs. After Fractional Photothermolysis
Before vs. After Fractional Photothermolysis
An image of Dr. Goverman’s patient before and after treatment with CO2 fractional photothermolysis. Nearly all patients in the study reported overall satisfaction with the result, showing a 50% reduction in pain, tightness and pruritus.
Source: Jeremy Goverman, MD

The results showed that 96.7% of the 387 patients reported overall satisfaction with laser therapy, citing a 50% reduction in neuropathic pain, tightness/contracture and pruritus.

Further Research on Fractional CO2 Laser Treatment

Given the promising results of their initial analysis, Dr. Goverman and his colleagues are now pursuing studies that aim to elucidate the treatment’s underlying mechanisms of action. One chief area of investigation will be the changes in gene expression that result from laser treatment, which can be observed in samples of scar tissue removed for other purposes that are subsequently laser treated. The scar tissue data will then be compared with existing research showing the laser’s effects on gene expression in normal skin to determine any differences.

The team is also developing a study to quantify the specific parameters of treatment for the fractional CO2 laser that confer the most beneficial effect—what doses of laser and treatment settings produce the best outcomes, what pattern of hole spacing and depth is most efficacious, how long after injury should the lasering be performed and what is the best time interval between laser treatments.

Another potential application of the fractional CO2 laser is for more effective drug delivery into the scarred tissue. It is already common practice for topical steroids to accompany treatment, with the laser facilitating deeper delivery via holes in the tissue. But it is also possible for other medications or stem cells to be delivered to the site with the laser. Future studies are still needed to ascertain which medications may improve the healing process.

References

(1) Hultman, C Scott, Jonathan S Friedstat, Renee E Edkins, Bruce A Cairns, and Anthony A Meyer. "Laser Resurfacing and Remodeling of Hypertrophic Burn Scars: The Results of a Large, Prospective, Before-After Cohort Study, With Long-Term Follow-up." Annals of Surgery, vol. 260, no. 3 (September 2014): 519-29.

(2) Anderson, R Rox, Matthias B Donelan, Chad Hivnor, Eric Greeson, E. Victor Ross, Peter R Shumaker, et al. "Laser Treatment of Traumatic Scars With an Emphasis on Ablative Fractional Laser Resurfacing: Consensus Report." JAMA Dermatology, vol. 150, no. 2 (February 2014): 187-93.

Contributor

  • Jeremy Goverman, MD, FACS
    Division of Burns
    Massachusetts General Hospital
    Assistant Professor of Surgery
    Harvard Medical School

This article first appeared in the Spring 2015 issue of Advances at Mass General

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