Total metastatic^a

N = 2627

<70 years^a

N = 359

≥70 years^a

N = 2268

Chemotherapy

HR

95% CI

HR

95% CI

HR

95% CI

Treated

ref

ref

ref

Not treated

1.095

1.00 - 1.20

1.455

1.08 - 1.96

1.166

1.06 - 1.29

Age at diagnosis

66 - 70

ref

ref

71 - 75

1.095

0.95 - 1.26

76 - 80

1.333

1.16 - 1.54

>80

1.707

1.48 - 1.96

Race/ethnicity

White

ref

ref

ref

Black

0.863

0.76 - 0.98

0.731

0.52 - 1.02

0.851

0.74 - 0.98

Others

0.795

0.64 - 0.99

0.760

0.36 - 1.60

0.781

0.62 - 0.98

Stage at initial diagnosis

Stage I

ref

ref

ref

Stage II

1.196

1.05 - 1.36

1.193

0.76 - 1.87

1.208

1.06 - 1.38

Stage III

1.424

1.22 - 1.66

1.825

1.10 - 3.02

1.455

1.24 - 1.71

Stage IV

1.609

1.40 - 1.85

2.170

1.38 - 3.42

1.564

1.35 - 1.82

PPI

No

ref

ref

ref

Yes

1.180

1.03 - 1.35

1.122

0.71 - 1.79

1.215

1.05 - 1.41

NCI comorbidity score

0

ref

ref

ref

1

1.236

1.11 - 1.38

0.773

0.55 - 1.09

1.304

1.16 - 1.46

2

1.046

0.90 - 1.22

1.268

0.74 - 2.17

1.055

0.90 - 1.24

≥3

1.424

1.21 - 1.67

1.907

1.24 - 2.94

1.339

1.12 - 1.60

Radiotherapy

No

ref

ref

ref

Yes

0.809

0.74 - 0.89

0.972

0.73 - 1.29

0.763

0.69 - 0.84

Breast cancer surgery

No

ref

ref

ref

Yes

0.618

0.55 - 0.70

0.438

0.32 - 0.61

0.663

0.58 - 0.76