Table 3. Results of the Cox regression analysis summarizing significant independent prognostic factors in the overall material.
| Factor | Hazard Ratio | 95% CI | P |
| Tumor depth | |||
| Superficial | 1.0 | ||
| Deep | 9.6 | 1.3–69 | 0.025 |
| Malignancy grade | <0.001* | ||
| 1 | 1.0 | ||
| 2 | 2.5 | 1.4–4.3 | 0.002 |
| 3 | 3.2 | 1.8–5.7 | <0.001 |
| Metastasis at the time of diagnosis | |||
| No | 1.0 | ||
| Yes | 1.8 | 1.2–2.9 | 0.010 |
| Surgery | |||
| Yes | 1.0 | ||
| No | 2.7 | 1.4–5.3 | 0.002 |
| Resection-margins | |||
| Free | 1.0 | ||
| Non-free | 2.9 | 1.9–4.4 | <0.001 |
| TGF-β1 | |||
| Low | 1.0 | ||
| High | 1.6 | 1.1–2.4 | 0.019 |
Abbreviations: TGF-β1, transforming growth factor beta 1.
*Overall significance as a prognostic factor.