Table 2 Multi-factorial analysis by three conceptual groups and final model

Family income

   Low & poor

1

0.039

99%

   Moderate

0.90 (0.70–1.15)

   Good

0.46 (0.23–0.90)

Smoking

   Non-smoker

1

0.016

99%

   Smoker

1.40 (1.07–1.86)

Metastasis to bone

   No

1

0.000

100%

   Yes

2.25 (1.43–3.52)

Metastasis to lung

   No

1

0.000

100%

   Yes

3.21 (1.70–6.05)

Tumour size

   ≤ 2 cm

1

0.000

88%

1

0.000

   >2 & <5 cm

1.43 (0.97–2.09)

1.43 (0.97–2.09)

   ≥ 5 cm

2.07 (1.39–3.09)

2.07 (1.39–3.10)

Tumour grade

   Well-differentiated

1

0.000

88%

1

0.000

   Moderately-differentiated

1.30 (0.88–1.93)

1.30 (0.88–1.93)

   Poorly-differentiated

2.33 (1.52–3.37)

2.33 (1.52–3.57)

No. of involved lymph nodes

   0

1

0.000

88%

1

0.000

   1–5

2.96 (1.78–4.94)

2.96 (1.78–4.94)

   6–10

5.29 (3.11–9.01)

5.29 (3.11–9.01)

   11–15

8.29 (4.98–13.80)

8.29 (4.98–13.80)

   >15

14.96 (8.83–25.33)

14.96 (8.83–25.33)

Lymph node ratio

   0

1

0.000

88%

1

0.000

   > 0 &≤ .3

2.02(1.30–3.13)

2.03 (1.09–3.76)

   > .3 &≤ .6

4.84 (2.72–8.60)

4.84 (2.72–8.60)

   > .6 &< 1

9.30 (5.48–15.80)

9.30 (5.48–15.80)

   1

15.31 (8.89–26.33)

15.31 (8.90–26.34)