Table 3 Univariate and multivariate analyses of OS in the models with or without SIS factor

Age (≤ 70 years vs. > 70 years)

1.34(0.94–1.89)

Gender (male vs. female)

0.90(0.62–1.32)

KPS (< 80 vs. ≥ 80)

0.70(0.38–1.30)

BMI(< 18.5 kg/m² vs. ≥ 18.5 kg/m²)

0.97(0.58–1.63)

Smoking status (no vs. yes)

0.80(0.57–1.13)

Tumour location (cervical + upper thoracic vs. middle and low thoracic)

1.73(1.20–2.49)

T stage (T1-2 vs. T3-4)

1.76(1.07–2.91)

1.83(1.10–3.04)

1.88(1.14–3.12)

N stage (N0 vs. N1)

1.22(0.80–1.86)

M stage (M0 vs. M1)

1.62(1.13–2.31)

1.70(1.16–2.49)

1.58(1.08–2.32)

Tumour TNM stage (I + II vs. III + IV)

1.74(1.10–2.73)

Radiotherapy techniques (2D-RT vs. 3D-RT/IMRT)

0.67(0.45–1.00)

Concurrent chemotherapy (0 vs. 1 vs. 2)

0.72(0.59–0.89)

0.74(0.59–0.92)

0.73(0.59–0.92)

Tumour early response(CR/PR vs. SD/PD)

1.31(0.90–1.90)

Family history of cancer (no vs. yes)

1.06(0.66–1.69)

NLR^c

1.12(1.04–1.20)

PLR^c

1.00(1.00–1.00)

1.00(1.00–1.00)

SII^c

1.00(1.00–1.00)

Alb^c

0.94(0.91–0.98)

0.95(0.91–0.99)

LMR^c

0.89(0.82–0.98)

SIS (0 vs. 1 vs. 2)

1.70(1.32–2.19)

1.50(1.15–1.96)