Efficacy Evaluation of Photodynamic Therapy for Oral Lichen Planus

A Systematic Review and Meta-analysis

Yuqing He; Jiaxin Deng; Yi Zhao; Huiqian Tao; Hongxia Dan; Hao Xu; Qianming Chen


BMC Oral Health. 2020;20(302) 

In This Article


Study Identification and Selection Criteria

The systematic review and meta-analysis were performed in accordance with the PRISMA statement,[11] as detailed in Additional file 1: Table S1. This study has been registered on the International Prospective Register of Systematic Reviews (PROSPERO) under the registration number CRD42020160512.

Electronic and manual literature searches were conducted in the following five electronic databases: PubMed, Web of Science, the Cochrane Library, Embase, and EBSCO up to 1 December, 2019. Search terms were: "Photodynamic therapy" OR "PDT" AND "lichen planus" OR "oral lichen planus" OR "OLP."

The inclusion criteria were: (a) original articles, clinical studies, and case series; (b) aim of the intervention was to evaluate the efficacy of PDT in the management of OLP; (c) lesion response was assessed and recorded; (d) articles published only in the English language; (e) clinical or histopathological diagnosis of OLP. The PICO questions below were applied:

  • Population (P): patients were diagnosed as OLP;

  • Intervention (I): patients were treated with PDT;

  • Comparison (C): condition of patients before PDT or topical corticosteroids;

  • Outcome (O): lesion response and lesion size of patients with OLP.

The exclusion criteria were: (a) reviews, abstracts, commentaries, letters to the editor, opinion articles, and animal studies; (b) inconsistent efficacy evaluation standard such that subsequent analysis cannot be performed; (c) individuals with idiopathic plaque-like lichen planus (non-erosive), lichenoid drug eruptions, or evidence of dysplasia in the tissue.

Data Extraction

Two authors (Z.Y. and D.J.X.) independently searched these five databases and assessed the titles and abstracts of all eligible publications. Details, including first author's name, publication year, type of PS, disease types, method of administration, disease location, and number of lesions, were collected from the included studies. Four outcome measures were collected for the efficacy evaluation: (a) lesion response, including complete response (CR), which means lack of visible lesion confirmed by clinical evaluation, and PR, which means lesion size decreased by at least 20%; (b) changes in lesion size/area; (c) Thongprasom sign (TH): score of 0 for normal healthy mucosa, 1 for lesions with only white striae, 2 for mixed keratotic and atrophic or erythematous lesions smaller than 1 cm2, 3 for keratotic and atrophic or erythematous lesions larger than 1 cm2, 4 for erosive/ulcerative lesions smaller than 1 cm2, and 5 for erosive/ulcerative lesions larger than 1 cm2; (d) visual analogue scale (VAS) rated by participants (score: 0–10): 0 means no symptoms and 10 means severe symptoms, as perceived by the patient.

Other parameters used for qualitative synthesis included wavelength, energy density of the laser, duration of irradiation, lesion dressing, treatment interval, relapse during follow-up, and adverse reactions during and after PDT.

Quality Assessment

The included randomised controlled trials (RCTs) were assessed by the Cochrane Collaboration's risk of bias assessment tool, with seven fields: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other bias.[12] The included non-RCTs were assessed by the Downs-Black Checklist, with 29 items.[13] The quality assessment was independently performed by two authors (H.Y.Q. and D.J.X.). Any conflicts were fully discussed and the corresponding authors (X.H. and C.Q.M.) would make the final decision.

Statistical Analysis

The I2 statistic and heterogeneity statistic Q were calculated to assess heterogeneity and the random effect model was utilised to assess heterogeneity when the I2 statistic was more than 50% or the p value of the Q test was less than 0.05.

The outcome measures in this study were VAS, TH, size, and response (PR and CR). The weighted mean differences of the first three continuous indexes were pooled by the inverse variance method (for the fixed effects model) and restricted maximum-likelihood (for the random effects model). The proportion and odds ratio (OR) of the response were pooled by the inverse variance method (for the fixed effects model) and the DerSimonian-Laird method (for the random effects model).

Publication bias was evaluated using a funnel plot and weighted linear regression was used to test funnel plot asymmetry if the number of the studies was not less than 10. Publication bias could be ignored when the p value was greater than 0.05.

Sensitivity analysis was utilised in subgroup and influence analyses. The light source, type of PS, administration method, and lesion location were considered for subgroup analysis and the u test was applied for the differential test between different subgroups. The influence analysis of the pooled estimates was conducted by the omission of one study at a time.

The Meta package of R software was applied for the analyses.[14]