Depth of invasion alone as a prognostic factor in low-risk early-stage oral cavity carcinoma

Objectives: To evaluate the significance of increasing depth of invasion (DOI) as the sole risk factor for recurrence in patients with low-risk early-stage oral cavity squamous cell carcinoma (OCSCC). Methods: We retrospectively reviewed 560 patients with OCSCC treated at our institution between 2003 and 2013. Patients were included if they had low-risk early-stage OCSCC treated with surgical resection ± neck dissection and no adjuvant therapy. Low risk was defined as absence of positive or close margins, lymphovascular invasion, perineural invasion, and positive lymph nodes. Patients with tumor (T)3-T4 disease were excluded. Pathology specimens were independently re-reviewed by two board-certified pathologists to confirm proper measurement of DOI. Kaplan-Meier and Cox proportional hazards regression analyses were performed to identify factors predictive for recurrence as well as progression-free survival (PFS) and overall survival (OS). Results: A total of 126 patients with low-risk early-stage T1-2N0 OCSCC were included. Median follow-up time was 42.5 months and median DOI was 4 mm. There was no significant difference in incidence of local (P = 0.95), regional (P = 0.81), or distant recurrence (P = 0.96) among patients with DOI < 4 mm versus ≥4 mm. On multivariable analysis, DOI was significant for both PFS (P = 0.03) and OS (P = 0.002). Conclusion: In this study, we show that in the absence of other high-risk pathologic features, DOI ≥ 4 mm does not portend for increased incidence of local, regional, or distant relapse in patients treated with surgery alone; however, increasing DOI is a marker for worse PFS and OS in patients with low-risk, early-stage OCSCC. Level of Evidence: 4. Laryngoscope, 129:2082–2086, 2019.