Table 3 Specification of the primary models for overall survival, locoregional control and freedom from distant metastasis

1

N stage: N0 vs N+

Sex: female vs male

N stage: N0 vs N+

2

T stage: T1–2 vs T3–4

N stage: N0 vs N+

T stage: T1–2 vs T3–4

3

Sex: female vs Male

T stage: T1–2 vs T3–4

Sex: female vs male

4

Age: modelled as a continuous, linear factor

Age: modelled as a continuous, linear factor

Age: modelled as a continuous, linear factor

5

Primary tumour GTV (cm³): modelled as a continuous, log-transformed factor

Primary tumour GTV (cm³): modelled as a continuous, log-transformed factor

Primary tumour GTV (cm³): modelled as a continuous, log-transformed factor

6

Primary tumour dose (EQD2): modelled as a continuous, linear factor

Primary tumour dose (EQD2): modelled as a continuous, linear factor

Primary tumour dose (EQD2): modelled as a continuous, linear factor

7

Histology: SCC vs basaloid SCC

Histology: SCC vs basaloid SCC

Histology: SCC vs basaloid SCC

8

Chemotherapy regimen: [no chemotherapy] vs [mitomycin C-based regimen] vs [cisplatin-based regimen]

Chemotherapy regimen: [no chemotherapy] vs [mitomycin C-based regimen] vs [icsplatin-based regimen];

Chemotherapy regimen: [no chemotherapy] vs [mitomycin C-based regimen] vs [cisplatin-based regimen];

9

RT technique: [3D-CRT] vs [IMRT] vs [VMAT]

RT technique: 3D-CRT vs IMRT vs VMAT

RT technique: 3D-CRT vs IMRT vs VMAT