Chemotherapy predictors and a time-dependent chemotherapy effect in metastatic esophageal cancer

Table 3 Univariate and multivariable analysis of patient and disease factors on overall survival in advanced esophageal cancer

Variable	Univariate		Multivariable1
	Hazard ratio (95%CI)	P value	Hazard ratio (95%CI)	P value
Chemotherapy
Chemotherapy received vs not received
If 0 < time ≤ 10 mo2	-	< 0.001	-	< 0.001
If time > 10 mo	0.95 (0.88-1.03)	0.204	0.98 (0.86-1.11)	0.699
Age	1.01 (1.01-1.01)	< 0.001	1.01 (1.00-1.01)	< 0.001
Gender
Female	0.99 (0.96-1.02)	0.420	0.90 (0.86-0.95)	< 0.001
Male	1 (reference)		1 (reference)
Race (combined)
Black	1.09 (1.05-1.14)	< 0.001	1.02 (0.96-1.09)	0.457
Other	0.86 (0.82-0.91)	< 0.001	0.87 (0.80-0.95)	0.002
White	1 (reference)		1 (reference)
Insurance type
Medicaid	1.28 (1.22-1.34)	< 0.001	1.21 (1.13-1.31)	< 0.001
Medicare	1.30 (1.26-1.33)	< 0.001	1.04 (0.99-1.10)	0.119
Other government	1.15 (1.04-1.26)	0.006	0.95 (0.82-1.10)	0.493
Not insured	1.37 (1.29-1.45)	< 0.001	1.20 (1.09-1.31)	< 0.001
Private	1 (reference)		1 (reference)
Income quartiles for place of residence
$30000-$34999	0.94 (0.90-0.98)	0.007	Dropped out of the model
$35000-$45999	0.93 (0.90-0.97)	< 0.001
$46000+	0.87 (0.83-0.90)	< 0.001
Less than $30000	1 (reference)
Treatment site
Academic	0.87 (0.85-0.89)	< 0.001	0.91 (0.87-0.94)	< 0.001
Non-academic	1 (reference)		1 (reference)
Geographic location in United States
Northeast	0.92 (0.89-0.96)	< 0.001	0.96 (0.90-1.02)	0.180
Midwest	1.02 (0.98-1.06)	0.340	1.07 (1.01-1.14)	0.032
South	1.03 (0.99-1.07)	0.142	1.05 (0.99-1.11)	0.138
West	1 (reference)		1 (reference)
Residence area type
Metro	0.93 (0.86-1.01)	0.086	Dropped out of the model
Urban	0.95 (0.87-1.03)	0.193
Rural	1 (Reference)
Number of comorbidities
1	1.20 (1.17-1.24)	< 0.001	1.09 (1.04-1.14)	< 0.001
≥ 2	1.45 (1.37-1.52)	< 0.001	1.16 (1.07-1.26)	< 0.001
0	1 (reference)		1 (reference)
Year of diagnosis
2010-2014	0.99 (0.96-1.01)	0.286	Dropped out of the model
2004-2009	1 (Reference)
Grade
2	1.08 (1.00-1.18)	0.065	1.06 (0.95-1.20)	0.297
3	1.30 (1.20-1.41)	< 0.001	1.28 (1.14-1.44)	< 0.001
4	1.30 (1.15-1.48)	< 0.001	1.21 (1.02-1.45)	0.032
1	1 (reference)		1 (reference)
AJCC T stage
pIS	0.57 (0.30-1.09)	0.090	1.11 (0.46-2.66)	0.821
T0	0.94 (0.69-1.26)	0.665	0.86 (0.59-1.25)	0.424
T1	0.88 (0.84-0.93)	< 0.001	0.89 (0.84-0.95)	< 0.001
T2	0.66 (0.62-0.69)	< 0.001	0.69 (0.65-0.74)	< 0.001
T3	0.65 (0.63-0.68)	< 0.001	0.73 (0.70-0.76)	< 0.001
T4	1 (reference)		1 (reference)
AJCC N stage
Positive	0.94 (0.91-0.97)	< 0.001	Dropped out of the model
Negative	1 (reference)

¹12370 observations were used in the multivariable model.

²As chemotherapy effect is not constant over time up to 10 mo, it was modeled with a time-dependent coefficient and the unadjusted hazard ratio for chemotherapy versus no chemotherapy is exp [-2.34 + 0.998 × log(time)] and adjusted hazard ratio is exp [-2.30 + 0.966 × log(time)].

AJCC: American Joint Committee on Cancer; CI: Confidence interval.