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Table 1 Characteristics of the study population.

From: Variables with time-varying effects and the Cox model: Some statistical concepts illustrated with a prognostic factor study in breast cancer

 

N

(%)

Year of diagnosis

  

1989

231

23.6

1990

207

21.1

1991

182

18.6

1992

189

19.3

1993

170

17.4

Metastases following surgery

  

Yes

264

27.0

No

715

73.0

Age at diagnosis

  

≤ 40 years

76

7.8

> 40 years

903

92.2

SBR Grade

  

Grade I

275

28.1

Grade II

444

45.3

Grade III

260

26.6

Tumor size

  

≤ 20 mm

753

76.9

> 20 mm

226

23.1

Lymph node involvement

  

No

554

56.6

Yes

425

43.4

Peritumoral vascular invasion

  

No

700

71.5

Yes

279

28.5

Hormone Receptor status

  

Both ER- and PR-

178

18.2

At least ER+ or PR+

801

81.8

Her2 status

  

Positive

100

10.2

Negative

879

89.8

Mib1 status

  

Negative

691

70.6

Positive

288

29.4