Kaplan-Meier survival curves for 270 patients with oral squamous cell carcinoma. Lymph node metastasis (a), primary site recurrence (b), distant metastasis (c), and disease-specific survival (d). Each consequence was stratified by a clinical event which effectively demonstrated influence of the factors. (a)-(c): Curves show 1 minus cumulative survival. (d): Curve shows cumulative survival.