Effect of fractional carbon dioxide laser combined with recombinant bovine basic fibroblast growth factor gel in the treatment of mature scar after facial scald burns: a retrospective cohort study

doi:10.21203/rs.3.rs-4830374/v1

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Effect of fractional carbon dioxide laser combined with recombinant bovine basic fibroblast growth factor gel in the treatment of mature scar after facial scald burns: a retrospective cohort study

https://doi.org/10.21203/rs.3.rs-4830374/v1

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Objectives

To assess the safety and clinical effect of fractional carbon dioxide (CO₂) laser combined with recombinant bovine basic fibroblast growth factor (rb-bFGF) in the treatment of mature scars after facial scald burns.

Methods

We collected 123 patients with mature scars after facial scald burns who received fractional CO₂ laser treatment in our department for a retrospective cohort study. According to whether the rb-bFGF gel was used during the treatment, patients were divided into CO₂ + rb-bFGF group and CO₂ group. The modified Patient and Observer Scar Assessment Scale (POSAS) scar score was used to evaluate the clinical effect. Patient satisfaction and adverse events were also assessed.

Results

At the last follow-up visit, the PSAS score was statistically different between the two groups (7.74 ± 2.15 vs. 9.41 ± 1.97; P < 0.01), including color (1.79 ± 0.77 vs. 2.80 ± 1.15; P < 0.01), stiffness (1.75 ± 0.62 vs. 2.00 ± 0.50; P < 0.01), and thickness (1.96 ± 0.48 vs. 2.16 ± 0.51; P < 0.01); the OSAS score was statistically different between the two groups (11.34 ± 3.21 vs. 12.96 ± 3.12; P < 0.01), including pigmentation (1.75 ± 0.78 vs. 2.61 ± 1.20; P < 0.01), thickness (1.92 ± 0.51 vs. 2.10 ± 0.42; P < 0.05), relief (1.64 ± 0.60 vs. 1.86 ± 0.50; P < 0.05), and pliability (1.96 ± 0.62 vs. 2.24 ± 0.52; P < 0.05). For patient satisfaction and adverse events, patients in the CO₂ + rb-bFGF group had faster wound healing, lower incidences of persistent erythema and hyperpigmentation, and higher satisfaction.

Conclusions

The effect of fractional CO₂ laser combined with rb-bFGF gel in the treatment of mature scar after facial scald burn is better than that of laser alone.

fractional carbon dioxide laser

recombinant bovine basic fibroblast growth factor

mature scar

scald burns

retrospective study

The fractional carbon dioxide (CO₂) lasers are widely used in scar treatment. With this technique, microscopic columns of skin called microscopic treatment zones (MTZs) are produced in the scar tissue, resulting in the generation of microscopic thermal wounds with sparing of the tissue surrounding each wound. At the molecular level, fractional laser treatment induces fibroblast apoptosis, upregulation of matrix metalloproteinases and heat shock proteins, alteration of types I and III procollagen levels [1–3]. However, clinical studies have found that after six sessions of fractional CO₂ laser treatment, scars improvement were excellent and good in 70% patients, and poor in 30% patients [4]. For Asian patients, the incidence of hyper-and hypo-pigmentation are prone higher [5]. Therefore, to improve the clinical efficacy and to reduce its complications are the main problems at present.

Basic fibroblast growth factor (bFGF) has been used in the treatment of acute burns, scalds and chronic wounds, which can promote collagen deposition, accelerate wound epithelialization and reduce the generation of secondary scars [6]. Some surgeons also use bFGF for acute wounds after laser treatment of scars to promote tissue repair, but there is still a lack of evidence-based knowledge on its safety and efficacy.

In order to assess the safety and clinical effect of fractional CO₂ laser combined with recombinant bovine basic fibroblast growth factor (rb-bFGF) in the treatment of mature scars after scald burns [7], we collected 123 patients with mature scars after facial scald burns who received fractional CO₂ laser treatment in our department from March 2017 to December 2022 for a retrospective cohort study.

Study design and patient enrollment

This retrospective cohort study is based on clinical and imaging findings of 123 patients with a diagnosis of mature scar after facial scald burns. We reviewed all the records of patients with mature scars (> 2 years) larger than 5 cm² after facial scald burns from March 2017 to December 2022. We included only patients who underwent 5 sessions of fractional CO₂ laser treatment and completed 6 follow-up visits (before treatment and 3 months after each treatment).

According to whether the rb-bFGF gel (Essex Bio-Technology, China) was used during the treatment, it was divided into CO₂ + rb-bFGF group and CO₂ group. There were 56 patients in CO₂ + rb-bFGF group, including 27 males and 29 females, with an average age of 25.09 ± 3.90 years. There were 67 patients in the CO₂ group, including 31 males and 36 females, with an average age of 25.74 ± 4.26 years.

Informed consent

was obtained from each subject prior to their treatment sessions. We have obtained consent for publication from each subject with consent forms fully understood and signed by all the participants themselves/legal guardian.

Treatment protocol

The entire scar of each patient was treated with 10600-nm fractional CO₂ laser (UltraPulse® Encore, Lumenis, Yokneam, Israel). The face was cleansed with mild soap and topical anaesthesia was applied using 5% compound lidocaine cream (Tongfang Pharmaceutical Group Co. Ltd., China) to the entire scar under occlusion for 60 min prior to laser therapy. The treatment parameters were determined based on each patient’s condition and availability as follows: Deep FX mode, Energy: 20 ~ 30 mJ, Frequency: 150 Hz, Density 5%. Scan Shape, and Spot Size were decided by shape and area of scar. The overlap rate of each scan was less than 5% and each treatment session encompassed the entire scar for one pass. Patients in CO₂ + rb-bFGF group were instructed to apply rb-bFGF gel to the treated area 4–6 times a day for 7 consecutive days after each session. We suggested daily use of a broad-spectrum sunscreen with a sun protection factor of 50 or higher after the laser wound healed completely to reduce the risk of post inflammatory hyperpigmentation (PIH). Sunscreen should be applied in an adequate amount in the morning and reapplied every two to three hours while outdoors.

Clinical outcome assessment

The primary outcome was the change from baseline in the modified Patient and Observer Scar Assessment Scale (POSAS) scar score evaluated by patients and 2 non-treating physicians at the last follow-up visit [8]. POSAS has two subscales investigating the opinion of patients (PSAS) versus professionals (OSAS). Each subscale contains six items: ‘scar-related pain’, ‘pruritus’, ‘color’, ‘stiffness’, ‘thickness’ and ‘irregularity’ for PSAS; ‘vascularity’, ‘pigmentation’, ‘thickness’, ‘relief’, ‘pliability’ and ‘surface area’ for OSAS. All items are scored on a 10‐point scale, with 1 indicating normal skin (no symptoms) and 10 reflecting the worst imaginable scar or sensation [9]. Since the patients in this study were basically free of pruritus and pain, the pruritus and pain scores were removed to reduce bias.

The secondary outcomes were patient satisfaction as assessed using a patient global assessment (PGA) score and adverse events [10]. Photographs of each patient before treatment and at each follow-up were captured. All photos were taken with the same digital camera (EOS 6D Mark Ⅱ, Canon, Japan) under consistent background, position, and lighting conditions. Based on the digital photos, self-assessment was performed by the patients using PGA scores ranging from 0 (no response) to 10 (maximum improvement) at the last follow-up visit. Duration of scab shedding and adverse events including persistent erythema (> 15 days), infection, hyperpigmentation, hypopigmentation, and scarring experienced by patients were noted and were statistically analyzed.

Statistical methods

Discrete categorical data are presented as the number and percentage; continuous data (except duration of scab shedding) are presented as the mean and SD. Duration of scab shedding is reported as median and minimum and maximum. Differences in continuous variables were assessed by the un-paired t-test, Mann-Whitney U-test and Fisher's exact test. Statistical significance was defined as P < 0.05. SPSS 22.0 for Windows was used for all statistical analyses.

There was no significant statistical difference in age, gender, Fitzpatrick's skin phototypes (SPT), duration of scar, PSAS score and OSAS score between the CO₂ + rb-bFGF group and CO₂ group before treatment (P > 0.05) (Table 1).

Table 1

Baseline characteristics of patients
	CO₂ + rb-bFGF group(N = 56)	CO₂ group(N = 67)	P-value
Age, years	25.09 ± 3.90	25.74 ± 4.26	> 0.05
Gender, n (%)			> 0.05
Male	27 (48.21)	31 (46.27)
Female	29 (51.79)	36 (53.73)
SPT, n (%)			> 0.05
Type Ⅲ	41 (73.21)	44 (65.67)
Type Ⅳ	15 (26.79)	23 (34.33)
Duration of scar, years	3.93 ± 4.22	4.19 ± 2.82	> 0.05
PSAS Score			> 0.05
Color	4.31 ± 1.75	4.16 ± 1.45
Stiffness	3.30 ± 0.77	3.02 ± 0.90
Thickness	3.34 ± 0.78	3.10 ± 0.80
Irregularity	4.23 ± 1.30	4.06 ± 1.07
Total PSAS Score	15.17 ± 3.85	14.34 ± 3.13
OSAS Score			> 0.05
Vascularization	3.15 ± 0.93	3.02 ± 0.95
Pigmentation	4.28 ± 1.90	4.33 ± 1.68
Thickness	3.17 ± 0.89	3.04 ± 0.84
Relief	3.55 ± 1.05	3.65 ± 1.23
Pliability	2.92 ± 0.84	2.69 ± 0.92
Surface Area	4.11 ± 1.42	4.10 ± 1.33
Total OSAS Score	21.28 ± 5.22	20.88 ± 4.08

From the pretreatment baseline to the 3-month posttreatment follow-up, two groups had a significant decrease in PSAS and OSAS scores ( CO₂ + rb-bFGF group: PSAS score:15.17 ± 3.85 vs. 7.74 ± 2.15, OSAS score: 21.28 ± 5.22 vs.11.34 ± 3.21; CO₂ group: PSAS score: 14.35 ± 3.13 vs. 9.41 ± 1.97, OSAS score:20.88 ± 4.08 vs. 12.96 ± 3.12 ) (Fig. 1, 2 ).

At the last follow-up visit, the PSAS score was statistically different between the CO₂ + rb-bFGF group and CO₂ group (7.74 ± 2.15 vs. 9.41 ± 1.97; P < 0.01) including color (1.79 ± 0.77 vs. 2.80 ± 1.15; P < 0.01), stiffness (1.75 ± 0.62 vs. 2.00 ± 0.50; P < 0.01), and thickness (1.96 ± 0.48 vs. 2.16 ± 0.51; P < 0.01), but no statistical differences in irregularity (2.23 ± 0.67 vs. 2.51 ± 0.68, P > 0.05); the OSAS score was statistically different between the CO₂ + rb-bFGF group and CO₂ group (11.34 ± 3.21 vs. 12.96 ± 3.12; P < 0.01) including pigmentation (1.75 ± 0.78 vs. 2.61 ± 1.20; P < 0.01), thickness (1.92 ± 0.51 vs. 2.10 ± 0.42; P < 0.05), relief (1.64 ± 0.60 vs. 1.86 ± 0.50; P < 0.05), and pliability (1.96 ± 0.62 vs. 2.24 ± 0.52; P < 0.05), but no statistical differences in vascularity (1.43 ± 0.57 vs. 1.55 ± 0.58; P > 0.05) and surface area ༈2.75 ± 1.05 vs. 2.87 ± 0.95; P > 0.05༉(Fig. 3).

A significant difference was observed in the comparison of the PGA scores between CO₂ + rb-bFGF group and CO₂ group (8.09 ± 0.60 vs. 7.02 ± 1.01; P < 0.01). Duration of scab shedding of CO₂ + rb-bFGF group was 4 (4, 6) days, significantly shorter than that of CO₂ group (7 (6, 10) days) (P < 0.01). Erythema lasting for more than 15 days was observed in 3 patients (5.36%) in CO₂ + rb-bFGF group throughout the treatment, which was significantly lower than 13 patients (19.40%) in CO₂ group (P < 0.05). Hyperpigmentation which gradually subsided within 12 weeks occurred in 6 patients in CO₂ group, while no patients in CO₂ + rb-bFGF group developed hyperpigmentation (P < 0.05). One patient (1.49%) in CO₂ group developed multiple areas of irregular texture and linear streaking which developed into scars (Fig. 4), while no such adverse event occurred in CO₂ + rb-bFGF group, but the difference between the two groups was not statistically significant (Table 2). No other adverse events such as hypopigmentation and infection occurred in the two groups.

Table 2

Patient satisfaction (PGA score) and adverse events
	CO₂ + rb-bFGF group(N = 56)	CO₂ group(N = 67)	P-value
PGA score, mean ± SD	8.11 ± 0.60	7.02 ± 1.01	< 0.01
Duration of scab shedding, days, median (min, max)	4 (4,6)	7 (6,10)	< 0.01
Persistent erythema, n (%)	3 (5.36)	13 (19.40)	< 0.05
Hyperpigmentation, n (%)	0	6 (8.96)	< 0.05
Scarring, n (%)	0	1 (1.49)	> 0.05

Evidence from recent years suggests that lasers are effective in treating multiple types of scars, and fractional laser treatments, especially ablative fractional laser therapy, have the greatest potential to treat the entire range of clinical issues with a single modality ^[11]. The fractional CO₂ lasers have the advantages of deep penetration, less damage and definite effect compared to the traditional ablative lasers, which has been the most important treatment for mature scars in our department for more than ten years. However, adverse events such as long downtime, persistent erythema and hyperpigmentation after treatment greatly affect patient satisfaction ^[12]. Therefore, we need to find ways to improve the efficacy of fractional CO₂ lasers and reduce adverse events.

It has been reported that bFGF has a major role in the wound healing process including inflammatory phase, proliferative phase and remodeling phase, which promotes wound healing and reduce scarring ^{[13, 14]}. Peng J et al. found that bFGF can increase the migration of keratinocytes and promote the migration of fibroblasts by regulating the synthesis and deposition of various extracellular matrix components, thus accelerating the formation and re-epithelialization of granulation tissue ^[15]. In this study, the duration of scab shedding of CO₂ + rb-bFGF group was about 3 days shorter than that of CO₂ group (P < 0.05), which may be due to the promotion of wound healing by topical rb-bFGF gel.

Sustained inflammation and proliferation may lead to pathological scarring, and erythema is a surrogate for inflammation/proliferation, so prolonged erythema can be a sign of an incipient pathological scar though erythema is a normal finding in the early phases of wound healing and scar formation ^[16–18]. The incidence of persistent erythema in CO₂ + rb-bFGF group was significantly lower than that in CO₂ group, suggesting that rb-bFGF may help shorten the inflammatory/proliferative phase, thereby reducing scar and improving the effect of laser treatment. After 5 sessions of treatment, POSAS scores in both groups showed significant decrease compared to baseline. However, in the comparison between the two groups, the color, stiffness, thickness and total score of PSAS score, and the pigmentation, thickness, relief, pliability, and total score of OSAS score of CO₂ + rb-bFGF group were significantly lower than those of CO₂ group. This result further indicated that rb-bFGF has the effect of reducing scar and improving the efficacy of fractional CO₂ lasers.

PIH after fractional laser treatment is common among Asians. One retrospective study of 961 successive 1,550-nm non-ablative fractional laser (NAFL) treatments revealed varied PIH rates of 2.6, 11.6, and 33% in patients with SPT III, IV, and V, respectively ^[19]. The incidence of PIH after ablative fractional laser (AFL) treatment may reach to 57.9% in patients with SPT III to V ^[20]. Persistent erythema suggests sustained inflammation and possibly a higher incidence of PIH. In this study, the incidences of persistent erythema and PIH in CO₂ + rb-bFGF group were higher than that in CO₂ group, which indicated that rb-bFGF reduced the inflammation and the occurrence of persistent erythema and PIH.

In this study, 1 patient in the CO₂ group had secondary scarring, and the incidence was slightly higher than that in the CO₂ + rb-bFGF group, but there was no statistical significance, which may be related to the small sample size. There was no secondary scarring in CO₂ + rb-bFGF group, which may be related to the fact that bFGF upregulated matrix metalloproteinase-1 expression in fibroblasts from hypertrophic scars, but not in fibroblasts from normal dermis, leading induced collagen degradation ^[21].

Patients in CO₂ + rb-bFGF group had higher satisfaction with the treatment, which may be due to the short downtime, less adverse reactions such as PIH, and better scar improvement. Therefore, combined with topical rb-bFGF gel can improve patients' satisfaction with fractional CO₂ laser treatment.

It has been demonstrated that bFGF could prevent pathological scarring through various mechanisms. In the remodeling phase, bFGF is one of the enhancers of degradation and replacement of type III collagen by type I collagen, which leads to the scar maturation ^{[22, 23]}. If elevated synthesis of type III collagen occurs in this phase, there is a high risk of pathological scarring. Therefore, the application of bFGF to the injured area soon after wounding may accelerate the appropriate deposition of the collagen, and this effect of local bFGF may help to prevent the onset of the chronic inflammation that drives pathological scarring ^[15]. It has also been revealed that bFGF may interfere with the formation of myofibroblasts, which is considered the most important mechanism underlying the development of keloids and hypertrophic scars ^[21]. Based on the evidence above, combined with the findings in this study, fractional lasers combined with rb-bFGF gel is also likely to achieve good results in the treatment of immature scars, which also brings new hints for the treatment of pathological scars.

In this study, the modified POSAS score was used to comprehensively evaluate mature scars before and after treatment from the perspective of researchers and patients, but there was still a lack of specific objective evaluation. Specific measurement values of relief, hemoglobin concentration and melanin concentration should be introduced for quantitative analysis to reduce the interference of subjective factors, which is more conducive to the clinical research of scar.

The effect of fractional CO₂ laser combined with rb-bFGF gel in the treatment of mature scar after facial scald burn is better than that of laser alone, with faster wound healing, lower incidences of persistent erythema and hyperpigmentation, better scar improvement, and higher patients’ satisfaction, which is worthy of further randomized controlled trials.

Funding

This work was funded by Shaanxi Provincial Science and Technology Department (CN) (Grand number is 2020GXLH-Y-023-1) and The Air Force Medical University (Grand number is 2023LC2345) received by Dr. Yue Yin.

Ethics approval

The study protocol was performed in accordance with the ethical guidelines of the 1975 Declaration of Helsinki and approved by the Institutional Medical Ethics Committee, and informed consent was taken from all the enrolled patients.

Conflict of interest

The authors declare no competing interests.

Author Contribution

Q.Y. and Y.Y. wrote the main manuscript text and W.D. did the statistical work. X.F. dealt with the tables. P.X. and T.L. prepared all the figures. All authors reviewed the manuscript.

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No competing interests reported.

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You are reading this latest preprint version

Effect of fractional carbon dioxide laser combined with recombinant bovine basic fibroblast growth factor gel in the treatment of mature scar after facial scald burns: a retrospective cohort study

Status:

Version 1

Abstract

Objectives

Methods

Results

Conclusions

Figures

INTRODUCTION

MATERIALS AND METHODS

Study design and patient enrollment

Treatment protocol

Clinical outcome assessment

Statistical methods

RESULTS

DISCUSSION

CONCLUSION

Declarations

References

Additional Declarations

Status:

Version 1