[A retrospective analysis on the malignant transformation rate, time and risk factors of oral leukoplakia].

Purpose: A retrospective analysis was made on the oral leukoplakia (OLK) patients archived from 1978 to 2009 at the Department of Oral Medicine, Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University, to analyze the malignant transformation of oral leukoplakia and its influential factors.

Methods: The data was studied with the SAS6.12 software package, using the methods of survival analysis and Cox regression to acquire malignant transformation rate (MTR) and malignant transformation time (MTT).

Results: According to the archived files, there were 576 cases of OLK with 350 males and 226 females. Among them, 66 cases (33 males and 33 females) developed OSCC, the total MTR was 11.46%. Two hundred and sixty-seven cases were suitable for survival analysis and Cox regression. The 1-year MTR was (0.40 ± 0.40)%, (0.86 ± 0.61)% (life-table method/product-limit method); the 2-year MTR went up to (2.84 ± 1.15)%, (2.93 ± 1.18)% and the 5-year MTR was as high as (11.28 ± 2.70)%, (11.31 ± 2.71)%. In Cox regression model, location of lesion and age were the main factors that affected OLK's transformation to OSCC.

Conclusions: The MTR of OLK is related to the follow-up time; The lesion site and age are the most important risk factors. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (08DZ2271100), Shanghai Leading Academic Discipline Project (S30260) and Research Fund of Shanghai Municipal Education Commission (JDY-07061).