Depth of invasion (DOI) as a predictor of cervical nodal metastasis and local recurrence in early stage squamous cell carcinoma of oral tongue (ESSCOT)

The new AJCC staging system (8th edition) incorporates depth of invasion to stage oral cancers. It is a recognized predictor for neck nodal metastasis and local recurrence, the associated risk is not well defined. The aim of this study was to explore the risk of occult neck nodal metastasis and local recurrence in relation to depth in early stage squamous cell carcinoma of oral tongue. We have evaluated records of 179 patients with early tongue cancer treated in our unit from 2006-2015 with a mean age of 57.92 ± 11.93 years. Treatment modalities used were surgery (26%), surgery followed by radiotherapy (64%) and chemo-radiation (10%). Neck dissection was ipsilateral in 94% and bilateral in 6% of the patients. Patients were grouped according to the AJCC cut off points in 8th edition for depth; group A: 1-5 mm (35%), group B: 6-10 mm (47%) and group C: > 10 mm (18%). Risk of local recurrence and nodal metastasis for Group A was 15% (10/63) and 23% (15/63), group B 20% (17/84) and 34% (29/84), and group C 40% (13/32) and 53% (17/32). Depth more than 10 mm is associated with significantly increased risk of recurrence and nodal metastasis. Elective neck dissection should be a consideration for tumors having depth less than 5mm.