Table 3 Univariate and multivariate analyses of prognostic factors influencing DFS

 Age (≤60 vs. >60)

1.223

0.699-2.139

0.480

 Sex (Male vs. Female)

0.580

0.331-1.015

0.057

 BMI (<24 vs. ≥24)

0.888

0.507-1.554

0.678

 Tobacco use (No vs. Yes)

1.218

0.714-2.080

0.469

 Alcohol use (No vs. Yes)

1.394

0.802-2.423

0.239

 Diabetes (No vs. Yes)

1.229

0.668-2.260

0.507

 Inferior gingiva

Ref

0.483

 Buccal mucosa

0.948

0.515-1.745

 Upper gingiva

1.437

0.697-2.962

 Exogenous

Ref

0.242

 Ulceration

1.460

0.721-2.957

 Infiltrating

0.884

0.411-1.898

 None

Ref

0.005

 Maxilla

3.955

1.751-8.936

 Mandible

3.135

1.487-6.613

 Both

3.577

1.342-9.533

 Skin invasion (No vs. Yes)

1.959

0.770-4.986

0.158

 I

Ref

0.082

 II

0.779

0.094-6.474

 III

0.000

0.000

 IV

2.299

0.317-16.686

 pT1

Ref

0.006

 pT2

1.115

0.137-9.074

 pT3

0.656

0.059-7.272

 pT4

3.326

0.457-24.190

 pN0

Ref

 pN1

1.108

0.480-2.556

 pN2

1.933

1.008-3.708

 pN3

5.860

2.470-13.903

 Well

Ref

0.591

 Moderate

0.614

0.163-2.318

 Poor

0.899

0.278-2.902

 ≤5 mm

Ref

0.111

 5-10 mm

1.599

0.765-3.342

 >10 mm

2.159

1.049-4.443

 Perineural invasion (Absence vs. Presence)

2.129

0.663-6.837

0.204

 Extracapsular invasion (Absence vs. Presence)

3.069

1.425-6.609

0.004

 Postoperative radiotherapy (No vs. Yes)

1.695

0.990-2.901

0.055

 pN stage

 pN0

Ref

 pN1

1.161

0.493-2.736

 pN2

1.844

0.914-3.719

0.087

 pN3

5.625

2.299-13.765

0.000

 None

Ref

0.007

 Maxilla

4.185

1.835-9.544

0.001

 Mandible

2.770

1.298-5.911

0.008

 Both

2.699

0.981-7.429

0.055