Table 5.

Validation of R classification system for predicting salivary gland cancer disease free survival (DFS) and disease specific survival (DSS) in FDSCC patients with neck dissection

Staging	Case No	5-year DFS	Log-rank χ2 (P value)	Multivariate analysis of DFSa			5-year DSS	Log-rank χ2 (P value)	Multivariate analysis of DSSb
				HR (95% CI)	C-index	AIC			HR (95% CIs)	C-index	AIC
N classification			25.096		0.73	400.009		10.799		0.734	106.753
N0	88	69.2	(< 0.001)	Reference			92.3	(0.005)	Reference
N1	14	71.4		0.541 (0.124–2.358)			85.7		1.914(0.199–18.460)
N2	52	30.9		3.235 (1.746–5.995)			66.9		6.552(1.764–24.330)
N3	0
R classification			43.897		0.72	397.649		37.986		0.796	98.113
R0	88	69.2	(< 0.001)	Reference			92.3	(< 0.001)	Reference
R1: 0–0.17	29	63.3		1.249 (0.535–2.918)			90.0		1.027(0.107–9.891)
R2: 0.17–0.56	21	34.6		2.527 (1.137–5.616)			71.4		4.715(0.949–23.429)
R3: > 0.56	16	0		7.007 (3.239–15.156)			0		21.677(5.285–88.916)
TNM staging c					0.663	412.414				0.736	110.621
TNM + R stagingd					0.728	402.68				0.856	103.149

^aN classification and R classification were adjusted for extraparenchymal invasion

^bN classification or R classification was the only prognostic variable kept in the Cox model

^cTNM staging was the only variable in the Cox regression model

^dBoth TNM staging and R classification were variables in the Cox regression model