Survival benefits and disparities in radiation therapy for elderly patients with pancreatic ductal adenocarcinoma

Table 3 Cox proportional hazards regression for overall survival and cancer-specific survival of elderly patients with pancreatic ductal adenocarcinoma between 2004 and 2018 from Surveillance, Epidemiology, and End Results database after propensity score matching

Variables	Subgroups	Overall survival				Cancer-specific survival
		Univariate analysis		Multivariate analysis		Univariate analysis		Multivariate analysis
		HR (95%CI)	P value	HR (95%CI)	P value	HR (95%CI)	P value	HR (95%CI)	P value
Age (yr)	65-80	Reference		Reference		Reference		Reference
	> 80	1.486 (1.367-1.615)	< 0.001	0.966 (0.852-1.095)	0.588	1.473 (1.352-1.605)	< 0.001	0.953 (0.838-1.084)	0.466
Year of diagnosis	2004-2010	Reference		Reference		Reference		Reference
	2011-2018	0.825 (0.774-0.880)	< 0.001	1.008 (0.894-1.137)	0.893	0.833 (0.780-0.889)	< 0.001	1.024 (0.905-1.159)	0.704
Sex	Female	Reference				Reference
	Male	0.997 (0.936-1.063)	0.932			0.986 (0.924-1.052)	0.67
Race	White	Reference				Reference
	Black	1.101 (0.988-1.227)	0.082			1.073 (0.959-1.201)	0.219
	Other	1.005 (0.907-1.114)	0.919			1.006 (0.905-1.117)	0.916
Marital status	Married	Reference		Reference		Reference		Reference
	Unmarried	1.217 (1.141-1.299)	< 0.001	1.061 (0.993-1.133)	0.08	1.226 (1.147-1.310)	< 0.001	1.065 (0.995-1.139)	0.068
Primary site	Head	Reference		Reference		Reference		Reference
	Body/tail	1.092 (1.006-1.185)	0.034	1.008 (0.927-1.096)	0.849	1.101 (1.013-1.197)	0.024	1.012 (0.929-1.103)	0.78
	Other	1.216 (1.106-1.336)	< 0.001	1.015 (0.922-1.118)	0.756	1.233 (1.120-1.358)	< 0.001	1.024 (0.929-1.130)	0.632
Histology grade	Grade I-II	Reference		Reference		Reference		Reference
	Grade III-IV	1.344 (1.219-1.482)	< 0.001	1.367 (1.240-1.508)	< 0.001	1.332 (1.204-1.473)	< 0.001	1.355 (1.224-1.500)	< 0.001
	Unknow	1.965 (1.818-2.125)	< 0.001	1.100 (1.005-1.204)	0.039	2.006 (1.851-2.173)	< 0.001	1.096 (0.999-1.203)	0.052
Node status	Negative	Reference		Reference		Reference		Reference
	Positive	0.835 (0.783-0.891)	< 0.001	1.209 (1.125-1.300)	< 0.001	0.837 (0.783-0.894)	< 0.001	1.227 (1.140-1.321)	< 0.001
Tumor size (cm)	< 2	Reference		Reference		Reference
	2-4	1.482 (1.317-1.668)	< 0.001	1.400 (1.242-1.578)	< 0.001	1.497 (1.325-1.692)	< 0.001	1.403 (1.239-1.587)	< 0.001
	> 4	1.854 (1.639-2.098)	< 0.001	1.505 (1.322-1.712)	< 0.001	1.875 (1.651-2.130)	< 0.001	1.492 (1.306-1.705)	< 0.001
SEER stage	Localized	Reference		Reference		Reference		Reference
	Regional	0.948 (0.860-1.045)	0.28	1.124 (1.009-1.252)	0.033	0.967 (0.874-1.070)	0.512	1.147 (1.026-1.282)	0.016
	Distant	2.058 (1.836-2.308)	< 0.001	1.723 (1.522-1.951)	< 0.001	2.154 (1.914-2.423)	< 0.001	1.782 (1.568-2.025)	< 0.001
Surgery	No	Reference		Reference		Reference		Reference
	Yes	0.337 (0.314-0.363)	< 0.001	0.352 (0.320-0.387)	< 0.001	0.322 (0.299-0.347)	< 0.001	0.334 (0.303-0.368)	< 0.001
Radiation	No	Reference		Reference		Reference		Reference
	Yes	0.850 (0.798-0.906)	< 0.001	0.818 (0.768-0.872)	< 0.001	0.851 (0.797-0.908)	< 0.001	0.816 (0.765-0.871)	< 0.001
Chemotherapy	No	Reference		Reference		Reference		Reference
	Yes	0.469 (0.428-0.513)	< 0.001	0.534 (0.485-0.589)	< 0.001	0.467 (0.425-0.512)	< 0.001	0.530 (0.480-0.586)	< 0.001

SEER: Surveillance, Epidemiology, and End Results; HR: Hazard ratio; CI: Confidence interval.