Table 2 Univariate and multivariate Cox regression analyses of the training group

Age,years

 20–35

Reference

Reference

 35–59

1.119 (0.639–1.96)

0.693

1.173 (0.680–2.025)

0.564

 60–84

1.234 (0.809–2.176)

0.466

1.279 (0.736–2.222)

0.381

 85 + 

2.393 (1.227–4.666)

0.010

2.362 (1.233–4.524)

< 0.01

Tumor size,cm

 ≤ 2 cm

Reference

 2.1-5 cm

0.849 (0.452–1.594)

0.611

—

—

 5.1-10 cm

1.584 (0.883–2.844)

0.122

—

—

 > 10 cm

1.217 (0.675–2.195)

0.513

—

—

Race

 Black

Reference

 White

1.107 (0.875–1.402)

0.394

—

—

 Other

0.830 (0.606–1.137)

0.247

—

—

Year of diagnosis

—

—

 2010–2011

Reference

 2012–2013

0.912 (0.737–1.128)

0.398

—

—

 2014–2015

0.868 (0.697–1.080)

0.205

—

—

Laterality

 Left

Reference

 Right

0.996 (0.838–1.184)

0.966

—

—

Primary site

 C50.0

Reference

 C50.1

0.924 (0.301–2.839)

0.891

—

—

 C50.2

1.118 (0.370–3.375)

0.842

—

—

 C50.3

1.651 (0.511–5.331)

0.401

—

—

 C50.4

1.316 (0.451–3.844)

0.615

—

—

 C50.5

1.401 (0.466–4.203)

0.547

—

—

 C50.6

0.331 (0.034–3.145)

0.336

—

—

 C50.8

1.165 (0.401–3.387)

0.779

—

—

 C50.9

1.272 (0.440–3.670)

0.656

—

—

Histopathology

 Ductal

Reference

Reference

 Lobular

2.089 (1.293–3.375)

0.003

1.907 (1.204–3.022)

< 0.01

 Other

1.289 (1.008–1.648)

0.042

1.232 (0.972–1.562)

0.083

Grade

 I ~ II

Reference

Reference

 III

1.547 (1.245–1.922)

< 0.01

1.607 (1.299–1.988)

< 0.01

 Unknown

1.528 (1.131–2.065)

0.005

1.473 (1.101–1.973)

< 0.01

T stage

 T1

Reference

 T2

1.661 (0.829–3.326)

0.151

—

—

 T3

1.011 (0.522–1.957)

0.973

—

—

 T4

1.270 (0.681–2.365)

0.451

—

—

N stage

 N0

Reference

 N1

1.187 (0.939–1.501)

0.151

—

—

 N2

1.258 (0.920–1.721)

0.149

—

—

 N3

1.182 (0.876–1.594)

0.272

—

—

Marital status

 Unmarried

Reference

Reference

 Married

1.093 (0.895–1.334)

0.380

1.039 (0.857–1.259)

0.694

 Other

1.428 (1.098–1.857)

0.007

1.347 (1.046–1.734)

0.021

Bone metastasis

 No

Reference

Reference

 Yes

1.564 (1.274–1.921)

< 0.01

1.551 (1.277–1.883)

< 0.01

 Unknown

2.535 (1.055–6.092)

0.037

2.899 (1.231–6.827)

0.014

Brain metastasis

 No

Reference

Reference

 Yes

2.140 (1.607–2.848)

< 0.01

1.964 (1.521–2.535)

< 0.01

 Unknown

1.157 (0.708–1.889)

0.559

1.242 (0.787–1.962)

0.351

Liver metastasis

 No

Reference

Reference

 Yes

1.517 (1.242–1.854)

< 0.01

1.560 (1.284–1.895)

< 0.01

 Unknown

0.772 (0.381–1.563)

0.472

0.732 (0.369–1.452)

0.372

HER2

 Negative

Reference

Reference

 Positive

0.585 (0.468–0.731)

< 0.01

0.586 (0.474–0.726)

< 0.01

 Unknown

0.941 (0.597–1.483)

0.793

0.953 (0.608–1.491)

0.833

ER

 Negative

Reference

Reference

 Positive

0.599 (0.458–0.785)

< 0.01

0.617 (0.473–0.804)

< 0.01

PR

 Negative

Reference

Reference

 Positive

0.626 (0.483–0.812)

< 0.01

0.622 (0.484–0.801)

< 0.01

Surgery

 No

Reference

Reference

 Yes

0.691 (0.539–0.883)

< 0.01

0.690 (0.546–0.871)

< 0.01

Neoadjuvant therapy

 No

Reference

Reference

 Yes

0.647 (0.460–0.911)

0.01

0.651 (0.471–0.901)

< 0.01

Chemotherapy

 No

Reference

Reference

 Yes

0.697 (0.568–0.856)

< 0.01

0.704 (0.576–0.862)

< 0.01

Radiotherapy

 No

Reference

 Yes

0.949 (0.770–1.170)

0.625

—

—