Differentiated Thyroid Cancer with Extrathyroidal Extension: Prognosis and the Role of External Beam Radiotherapy

Table 3

Multivariate analysis summary—Cox proportional hazards modeling. (**)

	CSS ($N=253$ with 26 events)		LRFR ($N=263$ with 41 events)
Variable	Hazard ratio (HR) (95% confidence interval (CI))	$P$ value	HR (95% CI)	$P$ value
Histology	8.7 (3.6–21.0)	$<$.0001
Age	3.1 (1.2–8.2)	.02	1.8 (0.9–3.7)	.09
Differentiation (*)
Tumor size	1.8 (0.7–4.6)	.25	2.1 (1.04–4.1)	.04
Postoperative status	7.1 (2.6–19.6)	.0001	4.6 (2.2–9.8)	$<$.0001
Neck metastasis			1.4 (0.8–2.7)	.26
Multifocal	0.3 (0.1–0.9)	.026
Margin status	1.3 (0.5–3.4)	.56
LVI (*)
T category (worst of pathology/OR)	1.2 (0.5–3.3)	.68
RAI	0.5 (0.1–1.9)	.29	0.9 (0.3–2.4)	.76
RT	0.9 (0.3–2.8)	.81	1.4 (0.7–2.9)	.36
SURGERY	0.6 (0.2–1.7)	.36	1.03 (0.5–2.0)	.93

(*) Not considered in the multivariate analysis because of the extent of missing data.
Note. Cox model was stratified by 3 approximately equal time periods: 1958–1971, 1972–1985, and 1986–1998 [11].