Post written by Daisuke Kikuchi, MD, PhD, from the Department of Gastroenterology, Toranomon Hospital, Tokyo, Japan.

We evaluated the risk factors of cervical lymph node metastasis (LNM) in 331 patients with superficial pharyngeal squamous cell carcinoma (PSCC) without a history of chemoradiotherapy for PSCC who underwent endoscopic submucosal dissection (ESD) at Toranomon Hospital in Tokyo, Japan.

We also investigated the correlation between tumor size and thickness because tumor size, rather than depth, is the dominant factor in the current TNM classification for PSCC.

Superficial PSCC has received increasing attention as a therapeutic target in the GI field with the recent innovations in ESD. The opportunities that endoscopists encounter PSCC are increasing because PSCC also is often detected as a metachronous cancer after the treatment of both esophageal squamous cell carcinoma and PSCC.

We have treated >600 lesions in >350 patients for 15 years at Toranomon Hospital. However, there are currently no defined criteria for the application of ESD to superficial PSCC. Considering that one of the serious issues we encounter during follow-up post-ESD is cervical LNM, identifying the clinicopathological predictors of cervical LNM would definitely help provide a basis for further therapeutic innovations.

For a large cohort of PSCC patients, we identified tumor thickness of ≥1000 μm and positive lymphatic invasion as significant independent predictors for cervical LNM. In particular, one of the landmark discoveries in the study is that both factors also were revealed to be significantly associated with cervical LNM even when the cases were limited to 204 with subepithelial invasion.

Although we found positive correlation between tumor thickness and size, there were noticeable variabilities in the values. We revealed that the tumor thickness was >1000 μm in 15.9% of PSCCs with tumor size of <20 mm (classified as T1), indicating that the current staging classification is inadequate to identify groups at high risk of cervical LNM. I am convinced that the time has arrived to establish ESD application criteria for superficial PSCC centered on tumor thickness and lymphatic invasion.

There is room for further innovation in ESD for PSCC, such as preoperative prediction of tumor thickness using magnifying endoscopy, application of an ultrathin scope for challenging cases, risk-based follow-up intervals, and improved postoperative chemotherapeutic regimens for high-risk cases. I hope that we can all collaborate on these improvements beyond facilities and national borders.

Graphical Abstract

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