Clinicopathological and prognostic characteristics of oral squamous cell carcinomas arising in patients with oral lichen planus: A systematic review and a comprehensive meta-analysis

Objectives: To evaluate current evidence in relation to the prognostic and clinicopathological significance of oral squamous cell carcinomas arising in patients with oral lichen planus (OLP-OSCC). Material and methods: We searched PubMed, Embase, Web of Science and Scopus for studies published before May-2019. We evaluated the quality of studies (QUIPS tool). We carried out meta-analyses to fulfill our objective. We examined the between-study heterogeneity and small-study effects, and conducted sensitivity and subgroup analyses. Results: Inclusion criteria were met by 27 studies (10,505 patients with OLP, of whom 205 developed a total of 247 OSCCs). The combined 5-year mortality rate was 15.48% for OLP-OSCC (95%CI = 7.34-25.19), clearly lower than the 34.70-50.00% mortality rate for conventional oral cancer communicated in previous official reports. Also, 14.67% (95%CI = 6.34-24.81) of OLP-OSCC developed N+ status, compared to 47.00% of conventional oral carcinomas. Likewise, most of the OSCCs in the study were T1/T2 (93.57%, 95%CI = 82.20-99.88) and presented at stage I/II (81.51%, 95%CI = 68.32-92.38) at the time of diagnosis, which contrasts with 50.00% of conventional carcinomas diagnosed in stages I/II. Furthermore, most of the cases were grade I (well differentiated OSCC) (67.79%; 95%CI = 43.50-88.65), in comparison to conventional OSCCs, which present typically in grade II in 90.00% of cases. Our results also show an 11.21% of the OLP-OSCC patients in this study developed multiple tumors. Conclusions: Oral squamous cell carcinomas that developed in oral lichen planus show favorable prognostic parameters, especially with regard to the mortality rate. Around 11% of OLP-OSCC patients develop multiple tumors, which confirms that OLP can lead to field cancerization.