# Elective Neck Dissection Strategies Guided by AJCC-8 Depth-of-Invasion (DOI) in cT1–T2N0 Oral Cavity Cancer—A Systematic Review

## TL;DR

This study reviews how using tumor depth to guide neck surgery in early oral cancer can improve survival and reduce unnecessary procedures.

## Contribution

The study identifies practical depth thresholds for elective neck dissection in early oral cancer based on tumor depth and clinical outcomes.

## Key findings

- Elective neck dissection at 3–4 mm tumor depth improves disease control and survival.
- Depth of invasion ≥ 5 mm increases risk of nodal failure.
- Diagnostic thresholds around 4 mm show high predictive value for metastasis.

## Abstract

There is often debate regarding whether to retain or remove lymph nodes in cases of early-stage oral cancer when they are not swollen. The 8th edition of the American Joint Committee on Cancer (AJCC) identifies the “depth of invasion” of a tumor as an indicator of potential metastasis or hidden spread; however, the optimal threshold for intervention remains uncertain. We have systematically reviewed relevant clinical studies that use “depth of invasion” to guide neck dissection in the early stages of oral cancer. The variables extracted from the data included hidden node rates and survival outcomes. Our qualitative synthesis indicates that the removal of neck nodes with a depth of 3 to 4 mm correlates with improved rates of disease control and survival. Avoiding needless surgical procedures is crucial when dealing with superficial tumors. These results provide plausibility to a selective, depth-guided approach to neck treatment, which can help guideline committees and doctors customize surgical plans for specific patients.

Background/Objectives: Clinically node-negative (cN0) neck management in cT1–T2 oral cavity squamous cell carcinoma continues to be a subject of controversy. The eighth edition AJCC has incorporated depth of invasion (DOI) as a significant factor in staging and consideration for possible neck dissection. Establishment of accurate DOI thresholds and their clinical relevance is crucial to maximize oncological outcomes with reduced unnecessary morbidity. Methods: A comprehensive analysis of clinical research assessing elective neck dissection (END) techniques in oral cavity cancers classified by DOI in cT1–T2N0 patients was carried out. The included studies reported occult nodal metastasis rates, overall survival, disease-specific survival, disease-free survival, and regional control. Results: With hazard ratios favoring END for overall survival (HR 0.64; 95% CI 0.45–0.92) and disease-free survival (HR 0.45; 95% CI 0.34–0.59), elective neck dissection provided advantages in both survival and regional control. In a national registry, DOI ≥ 5 mm independently raised the risk of nodal failure (HR 2.099; 95% CI 1.346–3.271), while END enhanced neck control in comparison to observation (HR 1.749; 95% CI 1.141–2.680). With ROC-derived cut-offs like 4.59 mm producing positive predictive values for nodal metastasis up to 41.7%, diagnostic thresholds clustered around 4 mm. Conclusions: Under DOI guidance, elective neck dissection consistently showed oncologic benefit, with practical thresholds convergent around 4 mm for sites in the mixed oral cavity and 3 mm for high-risk subsites. The synthesized results confirmed that DOI is the primary determinant of END when combined with histopathologic and subsite-specific risk factors.