Table 2. Univariate analysis of pathological characteristics impact on overall and progression-free survival.

Variables	Overall survival			Progression-free survival
	Events	HR (95% CI)	P	Events	HR (95% CI)	P
DTBC	64			41
Lower tertile	9	1		4	1
Intermediate tertile	26	3.0 (1.4-6.5)	0.004	15	4.0 (1.3-12.1)	0.01
Upper tertile	29	4.0 (1.9-8.4)	<0.001	22	7.1 (2.4-20.5)	<0.001
Lymph node metastasesa	67			49
None	36	1		25	1
Micrometastases and ITC	7	1.7 (0.7-3.8)	0.2	6	2.0 (0.8-4.8)	0.1
Macrometastases	24	3.8 (2.2-6.4)	<0.001	15	3.1 (1.6-5.8)	0.001
Differentiation grade	66			45
Well	14	1		8	1
Moderate	39	1.6 (0.9-3.0)	0.1	27	2.1 (1.3-3.6)	0.004
Poor	13	2.1 (1.0-4.5)	0.06	10	2.7 (1.5-4.9)	0.001
Absolute invasive depth	65	1.1 (1.0-1.2)	0.004	46	1.1 (1.0-1.2)	0.008
Invasive depth (>4 mm vs. <4 mm)	65	1.6 (1.0-2.5)	0.08	46	1.6 (0.9-3.0)	0.09
Stage (cT2 vs. cT1)	67	1.7 (1.0-2.7)	0.04	46	2.5 (1.4-4.4)	0.002
Tumor invasive front(Non-cohesive vs cohesive)	64	1.8 (1.1-3.0)	0.03	43	2.1 (1.1-4.2)	0.03
Perineural invasion (yes vs. no)	64	1.7 (1.0-2.9)	0.05	43	2.2 (1.2-4.0)	0.01
Tumor location	67			46
Floor of the mouth	28	1		22	1
Tongue	28	1.2 (0.7-2.0)	0.5	17	0.9 (0.5-1.7)	0.7
Other sub-sites	11	1.9 (0.9-3.8)	0.07	7	1.6 (0.7-3.8)	0.3
Age (per 1 year increment)	67	1.0 (1.0-1.1)	0.005	46	1.0 (1.0-1.0)	0.7
Smokingb (high vs. low)	58	1.5 (0.8-3.1)	0.2	41	0.8 (0.4-1.7)	0.6
Gender (male vs. female)	67	1.0 (0.6-1.6)	1	46	1.5 (0.8-2.6)	0.2

a: The size of the lymph node metastases found during primary surgical treatment.

b: Tobacco consumption was defined as high if the patient reported a history of >10 pack-years and as low if it was ≤ 10 pack-years.

Abbreviations: DTBC, Digital Tumor Bud Count, HR, hazard ratio, CI, confidence interval, ITC, isolated tumor cells.