Table 4 Univariate and multivariate analyses of PFS in the models with or without SIS factor

Age (< 70 years vs. ≥ 70 years)

1.23(0.84–1.80)

Gender (male vs. female)

0.77(0.51–1.16)

KPS (< 80 vs. ≥ 80)

0.92(0.45–1.88)

BMI(< 18.5 kg/m² vs. ≥ 18.5 kg/m²)

1.07(0.63–1.82)

Smoking status (no vs. yes)

0.65(0.45–0.94)

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

2.08(1.39–3.09)

1.75(1.14–2.70)

1.63(1.05–2.53)

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

1.67(0.97–2.89)

N stage (N0 vs. N1)

1.19(0.76–1.84)

M stage (M0 vs. M1)

1.97(1.36–2.85)

1.67(1.13–2.48)

1.60(1.07–2.38)

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

1.84(1.12–3.01)

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

0.57(0.38–0.86)

0.66(0.44–1.00)

0.65(0.43–0.98)

Concurrent chemotherapy (0 vs. 1 vs. 2)

0.79(0.64–0.98)

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

1.52(1.03–2.24)

1.70(1.14–2.53)

1.63(1.10–2.43)

Family history of cancer (no vs. yes)

1.30(0.81–2.08)

NLR^c

1.10(1.02–1.19)

PLR^c

1.00(1.00–1.00)

1.00(1.00–1.00)

SII^c

1.00(1.00–1.00)

Alb^c

0.95(0.91–0.99)

LMR^c

0.86(0.78–0.95)

SIS (0 vs. 1 vs. 2)

1.58(1.21–2.08)

1.40(1.06–1.88)