Evaluating photodynamic therapy for oral precancerous lesions: Highlighting outcome measure of malignant transformation.

The main outcome measure assessed in previous studies on photodynamic therapy (PDT) for oral precancerous lesions (OPL) is clinical response based on the alteration in lesion size after treatment. However, the primary and secondary outcome measures of the interventions for OPL should be malignant transformation and recurrence. Thus, the objective of this short communication is to summarize the evidence on PDT in preventing the recurrence and malignant transformation of OPL. There were 16 eligible studies which addressed the issue of OPL patients who received PDT with recurrence outcome, and the pooled recurrence rate (95% confidence interval) was analyzed to be 20.1% (16.2-24.6%). Notably, only 1 study reported that 7.5% of malignant transformation rate for OPL received PDT. These should be interpreted with caution due to low-level evidence, such as differences in study design, clinical and pathological features of patients enrolled, limited sample size, short follow-up time. Given few evaluated the effect of PDT on malignant transformation, we highlight that this primary outcome measure of OPL needs to be investigated in further well-designed longitudinal studies with adequate follow-up periods.