Table 4.

Cox regression analysis for overall survival by three risk groups according to Ang et al. or Rietbergen et al.

	All OPC		Only HPV positive
	P-value	Hazard ratio (95% CI)	P-value	Hazard ratio (95% CI)
Ang et al.
Intermediate vs. low risk	0.007	3.12 (1.36; 7.13)	0.011	3.07 (1.30; 7.26)
High vs. low risk	<0.001	3.75 (1.82; 7.78)
High vs. intermediate risk	0.466	1.21 (0.73; 1.99)
Rietbergen et al.
Intermediate vs. low risk	0.005	2.50 (1.32; 4.73)	0.009	2.93 (1.30; 6.57)
High vs. low risk	<0.001	3.00 (1.64; 5.46)
High vs. intermediate risk	0.392	1.20 (0.79; 1.83)

HPV+ patients are only classified in the low or intermediate risk group. Hazard ratio >(<1) means higher (lower) risk for the first category. CI, Confidence interval; OPC, oropharyngeal squamous cell carcinoma. Bold values p < 5% significance level.