Table 1. Oral cancer-free survival (OCFS) analysis of risk factors in transformation of oral leukoplakia.

Characteristic	Malignant events/n	OCFS rate at 3 yr (SE)	OCFS rate at 5 yr (SE)	P
All patients	57/320	0.866 (0.024)	0.820 (0.029)
Gender				0.141
Female	37/175	0.865 (0.032)	0.814 (0.039)
Male	20/145	0.867 (0.037)	0.830 (0.044)
Age (yr)				0.021
< = 60	38/228	0.880 (0.027)	0.849 (0.031)
>60	19/92	0.827 (0.052)	0.726 (0.071)
Lesion site				<0.001
Other sites	19/199	0.920 (0.024)	0.880 (0.032)
Lateral/ventral tongue	38/121	0.789 (0.046)	0.735 (0.052)
Lesion type				0.001
Homogenous	49/301	0.877 (0.024)	0.842 (0.029)
Non-homogenous	8/19	0.697 (0.116)	0.542 (0.132)
Epithelial dysplasia				<0.001
Low grade	27/229	0.937 (0.020)	0.905 (0.026)
High grade	30/91	0.675 (0.065)	0.590 (0.073)
Smoking				0.423
Never	33/194	0.868 (0.031)	0.816 (0.039)
Past and present	11/86	0.888 (0.044)	0.888 (0.044)
Unknown	13/40
Alcohol intake				0.689
Never	32/196	0.875 (0.031)	0.835 (0.037)
Past and present	12/84	0.876 (0.045)	0.847 (0.052)
Unknown	13/40

SE, standard error of the mean.