Cystic duct cancer: Should it be deemed as a type of gallbladder cancer?

Table 2 The COX multivariate analysis for cystic duct cancer, gallbladder cancer, and extrahepatic cholangiocarcinoma

Variable	OS			CSS
	HR	95%CI	P value	HR	95%CI	P value
Sex
Male	Ref			Ref
Female	0.886	0.838 to 0.938	< 0.001a	0.895	0.838 to 0.957	0.001a
Age at diagnosis	1.025	1.022 to 1.027	< 0.001a	1.022	1.019 to 1.025	< 0.001a
Year of diagnosis
2006 to 2009	Ref			Ref
2010 to 2013	0.938	0.889 to 0.990	0.019a	0.927	0.870 to 0.987	0.018a
Marital status
Married	Ref			Ref
Unmarried	0.839	0.794 to 0.887	< 0.001a	0.855	0.801 to 0.912	< 0.001a
Race			0.110			0.258
White	Ref			Ref
Black	0.929	0.857 to 1.007	0.074	0.941	0.856 to 1.033	0.200
Other	1.042	0.956 to 1.135	0.347	1.048	0.948 to 1.158	0.359
Tumor size	1.002	1.001 to 1.002	< 0.001a	1.003	1.002 to 1.004	< 0.001a
SEER historical stage			< 0.001a			< 0.001a
Distant	Ref			Ref
Regional	0.342	0.316 to 0.370	< 0.001a	0.277	0.252 to 0.306	< 0.001a
Localized	0.642	0.599 to 0.668	< 0.001a	0.613	0.566 to 0.664	< 0.001a
Surgical procedure			< 0.001a			< 0.001a
No operation	Ref			Ref
Partial resection	0.412	0.378 to 0.449	< 0.001a	0.395	0.356 to 0.438	< 0.001a
Total resection	0.403	0.373 to 0.435	< 0.001a	0.383	0.350 to 0.419	< 0.001a
Radical resection	0.359	0.330 to 0.391	< 0.001a	0.352	0.318 to 0.388	< 0.001a
Region			0.934			0.883
Alaska	Ref			Ref
East	1.081	0.623 to 1.878	0.781	1.055	0.593 to 1.878	0.855
Northern Plains	1.127	0.646 to 1.967	0.673	1.116	0.623 to 2.001	0.711
Pacific coast	1.088	0.628 to 1.885	0.764	1.052	0.593 to 1.867	0.863
Southwest	1.090	0.619 to 1.920	0.766	1.06	0.584 to 1.926	0.847
Histology
Adenocarcinoma	Ref			Ref
Others	1.186	1.094 to 1.285	< 0.001a	1.215	1.107 to 1.334	< 0.001a
Disease			< 0.001a			< 0.001a
CC	Ref			Ref
GC	1.494	0.980 to 2.279	0.062	1.348	0.845 to 2.151	0.210
EC	1.238	0.813 to 1.884	0.320	1.124	0.706 to 1.789	0.623

OS: Overall survival; CCS: Cancer-specific survival; HR: Hazard ratio; CC: Cystic duct cancer; GC: Gallbladder cancer; EC: Extrahepatic cholangiocarcinoma; SEER: Surveillance, Epidemiology, and End Results, CI: Confidence interval.

^aP < 0.05.