Table 2 Univariate Cox regression analysis of the whole cohort, the Right-sided cohort, and the Left-sided cohort

Age at diagnosis

< 0.001

< 0.001

  < 40

1.000

1.000

1.000

 40–49

1.101 (0.987–1.229)

1.080 (0.928–1.258)

0.319

1.126 (0.961–1.320)

0.143

 50–59

1.158 (1.048–1.279)

1.205 (1.051–1.381)

0.007

1.086 (0.938–1.256)

0.270

 60–69

1.557 (1.414–1.716)

1.499 (1.313–1.711)

< 0.001

1.523 (1.321–1.757)

< 0.001

  > 70

3.364 (3.063–3.695)

2.999 (2.636–3.411)

< 0.001

3.646 (3.178–4.183)

< 0.001

 Female vs. Male

0.989 (0.960–1.019)

0.475

0.875

0.839–0.913

< 0.001

Race

< 0.001

< 0.001

 Black

1.000

1.000

1.000

 White

0.994 (0.959–1.031)

1.056 (1.010–1.105)

0.017

0.879 (0.827–0.935)

< 0.001

 Hispanic/Latino

0.861 (0.730–1.016)

0.913 (0.743–1.122)

0/388

0.793 (0.601–1.046)

0.101

 Asian or Pacific Islander and others

0.699 (0.659–0.742)

0.766 (0.708–0.828)

< 0.001

0.671 (0.614–0.734)

< 0.001

 Unknown

0.445 (0.320–0.618)

0.449 (0.295–0.684)

< 0.001

0.449 (0.265–0.761)

0.003

 Yes vs. No

0.834 (0.799–0.871)

0.838 (0.793–0.885)

< 0.001

0.857 (0.798–0.921)

< 0.001

T stage

< 0.001

< 0.001

 T0–T2 (0, 2, 3)

1.000

1.000

1.000

 T3–T4 (4, 5)

1.973 (1.889–2.061)

1.784 (1.690–1.883)

< 0.001

2.212

2.055–2.381

 TX (6)

1.315 (0.900–1.922)

1.188 (0.714–1.976)

0.507

1.575 (0.891–2.786)

0.118

 N2 vs. N1

1.581 (1.543–1.620)

1.657 (1.608–1.707)

< 0.001

1.415 (1.355–1.477)

< 0.001

 Yes vs. No

0.408 (0.398–0.418)

0.430 (0.417–0.443)

< 0.001

0.386 (0.370–0.403)

< 0.001

Radiotherapy

< 0.001

0.001

 No

1.000

1.000

1.000

 Yes

0.517 (0.410–0.654)

0.637 (0.469–0.865)

0.004

0.508 (0.351–0.735)

< 0.001

 Unknown

0.524 (0.421–0.651)

0.515 (0.390–0.680)

< 0.001

0.506 (0.356–0.721)

< 0.001

Marital status

< 0.001

< 0.001

 Single, separated, divorced,

1.000

1.000

1.000

 Married (including common law)

0.843 (0.818–0.870)

0.872 (0.839–0.907)

< 0.001

0.788 (0.748–0.829)

< 0.001

 Widowed

1.681 (1.623–1.740)

1.592 (1.524–1.659)

< 0.001

1.746 (1.643–1.856)

< 0.001

 Unknown

1.065 (0.996–1.139)

1.082 (0.998–1.173)

0.056

0.984 (0.873–1.110)

0.792

Pathology grade

< 0.001

< 0.001

 Well-differentiated

1.000

1.000

1.000

 Moderately differentiated

1.119 (1.056–1.186)

1.197 (1.112–1.289)

< 0.001

1.020 (0.930–1.119)

0.669

 Poorly differentiated

1.635 (1.540–1.736)

1.673 (1.551–1.804)

< 0.001

1.436 (1.300–1.586)

< 0.001

 Undifferentiated

1.981 (1.825–2.150)

1.988 (1.802–2.192)

< 0.001

1.735 (1.476–2.040)

< 0.001

 Unknown

1.308 (1.188–1.439)

1.403 (1.247–1.578)

< 0.001

1.113 (0.942–1.315)

0.208

Positive lymph node

< 0.001

< 0.001

 0

1.000

1.000

1.000

 1

0.943 (0.851–1.045)

0.933 (0.819–1.062)

0.293

0.932 (0.787–1.105)

0.418

 2–3

1.085 (0.979–1.202)

1.082 (0.951–1.232)

0.232

1.058 (0.893–1.253)

0.514

 4–6

1.347 (1.215–1.495)

1.385 (1.216–1.578)

< 0.001

1.236 (1.041–1.467)

0.015

  ≥ 7

2.012 (1.814–2.232)

2.101 (1.844–2.393)

< 0.001

1.713 (1.441–2.035)

< 0.001

Lymph nodes ratio

< 0.001

< 0.001

  < 0.07

1.000

1.000

1.000

 0.07–0.25

1.312 (1.267–1.360)

1.375 (1.318–1.435)

< 0.001

1.245 (1.168–1.327)

< 0.001

 0.25–0.50

1.771 (1.704–1.842)

1.942 (1.853–2.036)

< 0.001

1.597 (1.490–1.711)

< 0.001

 0.50–1.0

2.873 (2.761–2.990)

3.302 (3.147–3.466)

< 0.001

2.446 (2.279–2.625)

< 0.001

 Left-sided vs. Right-sided

0.716 (0.698–0.734)

  ≥ 12 vs. < 12

0.758 (0.739–0.778)

0.692 (0.670–0.715)

< 0.001

0.765 (0.733–0.798)

< 0.001

^bTotal number of lymph node

0.985 (0.983–0.986)

0.980 (0.978–0.982)

< 0.001

0.986 (0.983–0.988)

< 0.001

  ≥ 11 vs. < 11

0.742 (0.706–0.779)

< 0.001