Utility of DOI and PNI in Conjunction as Prognosticators in Early-Stage OTSCC

Introduction: Oral tongue squamous cell carcinoma (OTSCC) is a challenging disease to treat as standard histopathology does not offer good prognostic information. Depth of Invasion (DOI) is a known histopathologic factor that is associated with poor prognosis in OTSCC. Perineural Invasion (PNI), however, has a controversial role in determining prognosis in early OTSCC.

Methods: This was a retrospective chart review of all patients at LUMC who have undergone primary surgical resection for OTSCC between 2015 and 2023. Only T1 and T2 tumors were included. T1s were split into two groups: T1s with diameter ≤ 2 cm with DOI ≤ 3 mm (shallow) and T1s with DOI 4-5 mm (deep). T2s were split into 2 groups: T2s with diameter 2-4 cm with DOI ≤ 5 mm (shallow) and T2s with diameter ≤ 4cm with DOI 6-10 mm (deep). The patient’s history, operative reports, surgical pathology reports, and postoperative clinic notes were reviewed.

Results: 88 patients were included. There were 34 T1s (25 shallow, 9 deep) and 54 T2s (12 shallow, 42 deep). There were no significant differences histologically between the two T1 groups. Of the T2s, deep T2s displayed more aggressive histological features. The deep tumors were more likely to have PNI (p=0.19), ENE (p=0.56), LVI (p=0.3), and WPOI 5 (p=0.088). T2s with higher DOI were more likely to recur, however these differences were not statistically significant. There were also no significant differences in survival between the two groups. Of those that recurred, there was no association with PNI.

Conclusions: T1 tumors split into shallow and deep groups according to DOI did not show significant histological differences, recurrence rates, or overall survival. Deep T2s compared to shallow T2s showed a higher propensity for PNI, ENE, LVI, WPOI 5, however these results were not statistically significant. Overall recurrence rates and survival did not differ between the deep and shallow T2 tumors. Therefore, based off our study, DOI and PNI were not useful prognosticators when used in conjunction for T1 and T2 OTSCC. This could suggest that at such an early stage, DOI and PNI are not as influential on prognosis as they are in later stage tumors.