Table 2. Descriptive and bivariate analysis of oral squamous cell carcinoma patients with or without somatic mutations of D-loop of mitochondrial DNA.

Variables	Total no. of patients (% in column)	No. of patients (%)		P value
		Mutation group (n = 75)	Non-mutation group (n = 45)
Age (yr)				0.961
< 49 years	47(39.2%)	30(63.8%)	17(36.2%)
> = 50 years	73(60.8%)	45(61.6%)	28(38.4%)
Gender				0.999 †
Female	12(10.0%)	8(66.7%)	4(33.3%)
Male	108(90.0%)	67(62.0%)	41(38.0%)
Personal Habit
Smoking	96(80.0%)	59(61.5%)	37(38.5%)	0.814
Alcohol	84(70.0%)	51(60.7%)	33(39.3%)	0.681
Betel quid	76(63.3%)	51(67.1%)	25(32.9%)	0.240
Primary tumor sites				0.157
Lip	2(1.7%)	2(100.0%)	0(0%)
Gum	2(1.7%)	1(50.0%)	1(50.0%)
Floor of mouth	3(2.5%)	2(66.7%)	1(33.3%)
Tongue	48(40.0%)	35(72.9%)	13(27.1%)
Buccal	33(27.5%)	22(66.7%)	11(33.3%)
Palate	8(6.7%)	4(50.0%)	4(50.0%)
Retromolar trigone	1(0.8%)	1(100.0%)	0(0%)
Tonsil	23(19.2%)	8(34.8%)	15(65.2%)
Histological features				0.307
Well differentiated	20(16.7%)	13(65.0%)	7(35.0%)
Moderately differentiated	62(51.7%)	42(67.7%)	20(32.3%)
Poorly or undifferentiated	38(31.7%)	20(52.6%)	18(47.4%)
Perineural invasion				0.917
Yes	30(25.0%)	19(63.3%)	11(36.7%)
No	90(75.0%)	56(62.2%)	34(37.8%)
Angiolymphatic invasion				0.231
Yes	30(25.0%)	16(53.3%)	14(46.7%)
No	90(75.0%)	59(65.6%)	31(34.4%)
Extranodal spread				0.081
Yes	19(15.8%)	8(42.1%)	11(57.9%)
No	101(84.2%)	67(66.3%)	34(33.7%)
Pathological stage				0.696
Stage I-II	36(30.0%)	23(63.9%)	13(36.1%)
Stage III-IV	84(70.0%)	51(60.7%)	33(39.3%)
Postoperative radiotherapy				0.952
Yes	97(80.8%)	60(61.9%)	37(38.1%)
No	23(19.2%)	15(65.2%)	8(34.8%)
Recurrence/distant metastasis				0.394
Yes	54(45.0%)	31(57.4%)	23(42.6%)
No	66(55.0%)	44(66.7%)	22(33.3%)

^† Fisher’s exact test