Table 5 Identification of the risk factors for developing metachronous lung metastasis in osteosarcoma patients using the Cox proportional hazard regression analysis

Age (year)

 ≤ 18

1.00 (Reference)

 19–40

0.758 (0.438–1.312)

0.323

  ≥ 41

0.717 (0.319–1.612)

0.421

Gender

 Male

1.00 (Reference)

 Female

0.631 (0.373–1.067)

0.086

Tumor site

 Upper limb

1.00 (Reference)

 Lower limb

0.891 (0.405–1.963)

0.775

 Spine-pelvis

2.024 (0.589–6.958)

0.263

Stage T

 T1

1.00 (Reference)

 T2

1.096 (0.650–1.849)

0.731

 T3

2.377 (0.319–17.718)

0.398

 Unknown

0.529 (0.071–3.94)

0.535

Stage N

 N0

1.00 (Reference)

 N1

25.026 (6.879–91.043)

0

 Unknown

1.106 (0.629–1.944)

0.727

Bone Mets

 No

1.00 (Reference)

1.00 (Reference)

 Yes

1.982 (1.164–3.373)

0.012

1.842 (1.053–3.224)

Surgery

 No

1.00 (Reference)

 Salvage

0.731 (0.174–3.075)

0.669

 Amputation

1.341 (0.32–5.609)

0.688

 Unknown

0.312 (0.044–2.222)

0.245

Chemotherapy

 No

1.00 (Reference)

 Yes

NA

NA

 Unknown

NA

NA

Necrosis

  < 90%

1.00 (Reference)

1.00 (Reference)

  ≥ 90%

0.158 (0.056–0.448)

0.001

0.143 (0.050–0.412)

 Unknown

0.470 (0.281–0.785)

0.004

0.515 (0.293–0.904)

Ki-67

  < 50%

1.00 (Reference)

1.00 (Reference)

  ≥ 50%

3.074 (1.183–7.987)

0.021

2.958 (1.098–7.969)

 Unknown

2.249 (1.058–4.779)

0.035

2.371 (1.112–5.056)

LDH

 Normal

1.00 (Reference)

1.00 (Reference)

 Elevated

2.082 (1.249–3.470)

0.005

1.791 (1.020–3.146)

ALP

Normal

1.00 (Reference)

1.00 (Reference)

 Within one time

1.222 (0.629–2.371)

0.554

1.256 (0.620–2.544)

 More than two times

2.262 (1.246–4.106)

0.007

1.317 (0.660–2.626)