Limited evidence for interventions to treat oral leukoplakia.

Data sourcesCochrane Oral Health's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline Ovid, Embase, Ovid, CancerLit via PubMed. MetaRegister of Controlled Trials, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform were searched for ongoing trials.The reference lists of included studies and existing reviews were manually searched.Study selectionRandomised control trials (RCTs) including patients diagnosed with oral leukoplakia comparing any treatment to placebo or no treatment were included with no restrictions on language or date of publication.Data extraction and synthesisTwo reviewers independently checked for inclusion, performed data extraction using a specially designed form, and assessed the risk of bias for each study and by domain over all studies. The primary outcome considered was onset of oral cancer reported as dichotomous data. Secondary outcomes were clinical resolution, histological changes and adverse events that were mostly reported as ordinal data.ResultsFourteen studies with 909 participants were included in the review. Of the included studies, four compared topical interventions to placebo, nine compared systemic interventions to placebo, and one compared a combination of topical and systemic treatments versus placebo. The risk of bias was considered to be low in one study, unclear in seven, and high for the remaining six. Only three studies provided usable data on the primary outcome: cancer incidence. Clinical improvement was achieved in three studies using: systemic vitamin A or retinoids (two studies) and systemic beta-carotene or carotenoids (one study). Only two studies using beta-carotene or carotenoids were meta-analysed, showing no benefit on the outcome cancer development.ConclusionsThere is no evidence that any of the active treatments included work better than placebo in reducing the risk of developing oral cancer.