Background: In early oral tongue cancer, depth of invasion (DOI) of 4 mm or greater is thought to increase the risk of nodal metastasis. Current data suggests that the presence of micrometastasis is 25-30%, however, this is primarily determined from pathologic evaluation of patients who undergo elective neck dissection (END). The rates of neck recurrence in patients with DOI of 4 mm or greater who observe the neck is not known.
Objective: To determine the rates of neck recurrence in patients with early oral tongue cancer and DOI 4 mm or greater who forego END.
Methods: Patients with early tongue cancers who underwent glossectomy alone at Vanderbilt Medical Center between 2000-2015 were identified through the electronic medical record. Chart review further defined treatment outcomes and follow up. Pathological data, including margin assessment, DOI, and perineural invasion was additionally reviewed. Stata 15.0 was used for statistical analysis.
Results: Review identified 93 patients with T1 or T2 tongue cancer and clinically N0 neck disease who underwent glossectomy without END. The average age of the cohort was 59 years (range 33-84). Of these, there was slight male predominance, with 57 males (61%) and 36 females (39%). All patients had squamous cell carcinoma, and five of these had verrucous carcinoma. Two patients formerly used smokeless chewing tobacco and two continued use. 83 patients had T1 lesions (89%) and the remaining 10 were T2 (11%). The average follow up was 51.2 months (range 0-225). Of those with at least 2 years of follow up, 37 of 74 patients recurred (50%), with 15 recurring in the oral cavity (21%) and 21 with nodal metastasis (28%).
There were 23 patients with DOI of 4 mm or greater and 40 patients with DOI less than 4 mm with appropriate follow up. 65% of patients with DOI of 4 mm or greater (n=15) recurred in the neck, while only 12.5% (n=5) with a DOI less than 4 mm recurred in the neck (OR 13.1, 95% 3.6-445, p<0.0001). The average time for recurrence was 20.1 months for patients with 4 mm or greater DOI and 28.2 months for those with DOI less than 4 mm.
One patient had no follow up following surgical excision, 17 pathological specimens did not expressly state DOI, and 15 patients had tongue recurrence, leaving 64 patients who underwent time-to-event analysis. The recurrence rate differed significantly by DOI (p<0.0001 log rank test). Kaplan-Meier failure rates at two years was 6% in those with DOI <4 mm and 46% in those with DOI of 4 mm or greater. Overall, there was a 7.5 fold (95% 2.7-21) increase in the hazard for recurrence in those with greater DOI.
Conclusion: Patients with early oral tongue squamous cell carcinoma and DOI of 4 mm or greater who do not undergo END have a substantially increased risk of nodal metastasis. If surgical pathology indicates a tumor depth of 4 mm or greater, the patient may have greater risk of occult nodal disease than previously believed based on pathology alone.