Comparison of Ultrasound-Assisted Low-Dose Versus Medium-Dose 5-Fluorouracil and Triamcinolone Acetonide in the Treatment of Hypertrophic Scar

. Intralesional 5-fuorouracil (5-FU) and triamcinolone acetonide (TAC) injection is efective for the treatment of hypertrophic scar. Te side efects of current that recommended 45mg/ml (high-dose) 5-FU have been reported. However, no previous study has investigated the efcacy and safety of low-dose (2.5mg/ml) 5-FU with 4 mg/ml TAC or medium-dose (10mg/ml) 5-FU with 4 mg/ml TAC for treatment of hypertrophic scar. Herein, a retrospective comparative study was conducted. Te records of 70 patients, treated with low-dose (2.5mg/ml) 5-FU and 4mg/ml TAC every 4weeks (Group 1) or medium-dose (10mg/ml) 5-FU and 4mg/ml TAC every 4weeks (Group 2), were analyzed. Te Vancouver Scar Scale (VSS), vascularity, and thickness of hypertrophic scar at baseline and at 7th-treatment (each group received 6 treatment sessions) were compared. Te ultrasound showed the large vascular distribution in scar margins. Both groups gained clinical improvement in VSS, vascularity, and thickness. Group 2 (medium-dose) exhibited signifcantly better improvement than Group 1 (low-dose). However, the overall side efects rate was 11.4% in Group 1, signifcantly lower than 31.4% in Group 2. Scar margins were suggested to be target sites for injection. Medium-dose (10mg/ml) 5-FU +4mg/ml TAC could efectively reduce the thickness of hypertrophic scar; however, the side efects rate was also higher in medium-dose group than in low-dose group.


Introduction
Hypertrophic scar is a fbroproliferative skin disease characterized by disordered collagen accumulation.It is still a major clinical problem although various treatments [1] (including the silicon-based products, agents' injection, surgical intervention, radiotherapy, and laser therapy) are suggested.Among these treatments, combination 5-FU with corticosteroid injection is useful for hypertrophic scar treatment.Fitzpatrick [2] frst proposes the 50 mg/ml 5-FU for the treatment of hypertrophic scar.Recently, Jiang et al. [3] conducted a meta-analysis of 6 trials from USA, Pakistan, Iran, India, and Tailand.In these trials, the high-dose (45 mg/ml) of 5-FU combined with TAC is recommended and applied; the dosage in 5 trials is 4 mg/ml TAC and 45 mg/ml 5-FU, while in 1 trial is 1 mg/ml TAC and 45 mg/ ml 5-FU [4][5][6][7][8][9].Te topical 5-FU injection with TAC is efective; however, side efects associated with high-dose 5-FU injection, including the extreme pain and ulcerations, are addressed [10].Laser-assisted topical steroid injection with 10 mg/ml TAC is efective for keloid [11], while there is no comparative study investigating the efcacy and safety of high-dose (45 mg/ml) or medium-dose (10 mg/ml) or lowdose (2.5 mg/ml) 5-FU combined with TAC in treatment of hypertrophic scar.
Diferent from well recognized standard of 45 mg/ml (high-dose) 5-FU, the drug strength of 5-FU in China is 25 mg/ml [12,13], and we previously treated patients with medium-dose (10 mg/ml) and low-dose (2.5 mg/ml) 5-FU and TAC.Tus, we retrospectively compared the efcacy and safety of medium-dose or low-dose 5-FU combined with TAC in treatment of hypertrophic scar.
In the abovementioned 6 trials, the drug is injected until slight blanching is observed and the maximum volume is less than 0.5 ml/cm 2 .However, the hypertrophic scar presents various thicknesses in clinic; thus, there is limitation in calculating the amount of drug according to area instead of volume.Until now, there is lack of accurate record for the drug dosage per unit volume and lack of comparative study for the efect of drug at diferent concentrations.Tus, further investigations are needed.
Herein, we conducted a comparative study to evaluate the efcacy and safety of ultrasound-assisted 10 mg/ml and 2.5 mg/ml 5-FU and TAC for hypertrophic scar.

Material and Methods
Following institutional review board approval, detailed patients' characteristics were collected from their medical records.Patients receiving less than 6 treatment sessions were excluded.Tirty-fve patients received 2.5 mg/ml 5-FU (Shanghai Xudong Haipu pharmaceutical Co, Ltd., China, 0.25 g/10 ml) and 4 mg/ml TAC (Kunming Jida pharmaceutical Co, Ltd., China, 40 mg/1 ml) every 4 weeks (low-dose group), while 35 patients received 10 mg/ml 5-FU and 4 mg/ml TAC every 4 weeks (medium-dose group) at Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, between Jan 2020 and Aug 2021.Te study was conducted according to the Declaration of Helsinki, and informed consent was obtained from the participants.
Each time before injection, all the patients were photographed and received B ultrasound examination performed by surgeon and sonographer in our groups, respectively.Te surface areas were estimated with the ruler.Ten, the total volume of hypertrophic scar was obtained with the length, width, and thickness.For Group 1 (lowdose), the 4 ml 0.2% lidocaine was used to dilute with 0.5 ml 5-FU and 0.5 ml TAC in a 5 ml syringe.For Group 2 (medium-dose), the 2.5 ml 0.2% lidocaine was used to dilute with 2 ml 5-FU and 0.5 ml TAC in a 5 ml syringe.Te mixed solution was transferred into 1 ml syringe and injected with 30-gauge needle, until slight blanching was noticed.Te spacing between injected points was approximately 1 cm.Te central area of hypertrophic scar was dense with collagen deposition, and the drug was difcult to inject and infltrate.By analyzing the data of B ultrasound, we mainly injected the drug into the bilateral sides as well as the superfcial surface (marginal area).Te injected solution dose was recorded to calculate the dose per unit volume.

Outcome Evaluation.
Te records of patients at baseline and at 7th-treatment (each group received 6 treatment sessions) were analyzed.Te hypertrophic scars were assessed with two blinded plastic surgeons in our groups using the Vancouver Scar Scale.Te thickness of hypertrophic scar was assessed with high-resolution ultrasound with 22-MHz probe (Esaote Mylab).Te ultrasound assessment and related data analysis were performed by our experienced sonographer, Angang Ding.Te thickness of hypertrophic scar was the distance between the ultrasound gel/epidermis border and dermis/subcutaneous fat border.If the shape of hypertrophic scar was irregular, the ultrasound measurements were repeated three times to obtain a mean thickness.Te color Doppler was used to detect the vascularity of hypertrophic scar.

Statistical Analysis.
Statistical analyses were performed with SPSS version 11.For comparison of the outcome of pretreatment and post-treatment in each group and between two groups, student's t-test and chi-square tests were used.Te P value less than 0.05 was considered statistically signifcant.

Clinical Characteristics of Patients.
Of the 70 patients of hypertrophic scar included in this study, 35 received 2.5 mg/ ml 5-FU with 4 mg/ml TAC every 4 weeks and 35 received 10 mg/ml 5-FU and 4 mg/ml TAC every 4 weeks.Te Fitzpatrick skin types of included patients were III-IV.Te clinical characteristics of patients are summarized in Table 1.Te main cause of hypertrophic scar is surgery.Te mean duration of the lesion was 9.6 ± 5.5 months in Group 1 and 8.7.3 ± 6.3 months in Group 2. With ultrasound evaluation, we also observed that most vascular supply for the hypertrophic scar was located near bilateral margins (Supplemental Figure 1).

Vascularity.
Te ultrasound evaluation showed the signifcant improvement in vascularity following treatment in both groups (Figures 1(c) and 1(f ) and Figures 2(c) and 2(f ).

Side Efects.
Te overall side efect rates in Group 1 (11.4%) were signifcantly lower than those in Group 2 (28.6%).Among them, several patients experienced more than one side efect.Te main side efects were erythema, ulceration, and hyperpigmentation.No skin telangiectasia was observed or reported in the participants (Table 4).
Tis is the frst study to assess the use of low-dose and medium-dose 5-FU with 4 mg/ml TAC every 4 weeks for hypertrophic scar.Both the low-dose 5-FU with TAC and medium-dose 5-FU with TAC were proven to be efcient while the medium-dose group had better clinical outcomes compared with the low-dose group.Meanwhile, more side efects were observed in medium-dose 5-FU combined with TAC compared with the low-dose 5-FU combined with TAC.Te ulceration rates in low-dose group and mediumdose group were 2.9% and 11.4%, respectively, which were lower than high-dose group (21.4% or 30%) as previously reported [17,18].As the drug strength of 5-FU in China is 25 mg/ml [13], there were no data about high-dose 5-FU + TAC in the treatment of hypertrophic scar in the current study.
Consider that the formation and progression of hypertrophic scar depended on the cell proliferation of fbroblasts and collagen secretion, which in turn depended on the blood supply.We speculated that injection near the large blood vessels previously marked by ultrasound could lead to vascular atrophy, which accelerated the inhibition of hypertrophic scar.Tus, it is important to investigate a safe and practical chemotherapeutic therapy with the ultrasound assistance for the hypertrophic scar.Our ultrasound data showed the large blood supply mainly located in the bilateral margin of the hypertrophic scar.With ultrasound, we also observed that the injection targeting the bilateral margins of hypertrophic scar could reduce the vascularity of hypertrophic scar.
In addition, compared with Vancouver Scar Scale (VSS), a subjective tool, mostly used in clinical application, the ultrasound could provide a noninvasive objective assessment including the thickness and vascularity.We demonstrated that ultrasound not only provided an accurate volume information of scar lesion for injection but also was reliable for assessment therapeutic outcome.Compared with optical coherence tomography (OCT), ultrasound has deeper penetration, while OCT has better and fner image resolution than ultrasound [19]; it could be an alternative objective tool for evaluating the outcome for hypertrophic scar treatment, which deserves further investigation.

Conclusion
Medium-dose 5-FU combined with TAC is more efective than low-dose group, while the rate of side efects is higher in the medium-dose group.Ultrasound is useful for evaluating the efects of hypertrophic scar intervention.

Figure 1 :
Figure 1: Representative case in Group 1.A 30-year-old female had postoperation hypertrophic scar in the forearm for 6 months.(a, d) Following the 6 sessions of low-dose 5-FU and TAC treatment, clinical improvement was obtained.(b, e) Te ultrasound imaging showed the thickness of hypertrophic scar was reduced.(c, f ) Te ultrasound imaging showed the vascularity reduction following the injection treatment.

Figure 2 :
Figure 2: Representative case in Group 2. A 34-year-old female had post-operation hypertrophic scar in shoulder for 8 months.(a, d) Following the 6 sessions of medium-dose 5-FU and TAC treatment, the hypertrophic scar was markedly fatter.(b, e) Te ultrasound imaging showed the thickness of hypertrophic scar was reduced.(c, f ) Te ultrasound imaging showed the vascularity reduction following the injection treatment.

Table 2 :
Comparison of outcome in each group (pretopical injection and post topical injection).

Table 3 :
Comparison of efect between two groups.

Table 1 :
Characteristics of patients.

Table 4 :
Comparison of side efects between two groups.