Analysis of lymph node metastasis for hypopharyngeal carcinoma based on computed tomography

Abstract

Objective To explore the pattern of lymph node metastasis and provide guidance for the delineation of clinical target volume for patients diagnosed with hypopharyngeal squamous cell carcinoma (HSCC). Methods A total of 123 patients who were initially diagnosed with HSCC by electrolaryngoscope and computed tomography (CT) of the head and neck in Shandong Tumor Hospital between 2014 and 2017 were recruited in this study. The lymph node metastasis was evaluated based on the diagnostic criteria of CT scan. The lymphatic metastasis ratio (LMR) at each node level was calculated. Analysis of variance (ANOVA) and χ2 test were used to analyze the relationship between LMR and primary tumors. Results Among 123 patients, primary tumors were originated from the pyriform sinus (PS) in 101 cases (82.1%), posterior pharyngeal wall (PPW) in 15(12.2%) and postcricoid (PC) in 7(5.7%), respectively. The overall LMR was calculated as 84.6%(n=104), in detail, 84.2% for patients with primary tumors originating from PS, 93.3% for those from PPW and 71.4% for patients from PC, respectively. For PS-derived tumors, the ipsilateral neck LMR at the level Ⅰa, Ⅰb, Ⅱa, Ⅱb, Ⅲ, Ⅳ, Ⅴ, Ⅵa, Ⅵb, and Ⅶ was 0, 3.0%, 66.3%, 42.6%, 46.5%, 10.9%, 5.0%, 2.0%, 7.9%, and 11.9%, respectively, and 0, 0, 14.9%, 5.0%, 3.0%, 2.0%, 0, 0, 3.0%, and 2.0% for the contralateral neck. For PPW tumors, the ipsilateral neck LMR at the level Ⅰa, Ⅰb, Ⅱa, Ⅱb, Ⅲ, Ⅳ, Ⅴ, Ⅵa, Ⅵb, and Ⅶ was 6.7%, 6.7%, 66.7%, 46.7%, 46.7%, 20.0%, 0, 13.3%, 33.3%, and 60.0%, respectively, and 6.7%, 6.7%, 33.3%, 26.7%, 20.0%, 20.0%, 0, 0, 13.3%, and 33.3% for the contralateral neck. For PC tumors, the ipsilateral neck LMR at the level Ⅱa, Ⅱb, Ⅲ, Ⅳ, Ⅴ and Ⅵb was 71.4%, 28.6%, 14.3%, 14.0%, 14.0%, and 14.3%, respectively, and the LMR at the level Ⅱa was 14.3% for the contralateral neck. No lymph node metastasis occurred in other lymph node levels. The mean levels of lymph node metastasis for the T1-T4 stage tumors were 2.4, 1.9, 2.2, 3.3 with statistical significance (P=0.023), and 2.2, 4.5 and 1.6 for patients with the tumors originated from PS, PPW and PC (P=0.000). The PPW invasion was significantly correlated with the level Ⅶ metastasis (P=0.000), and PC or esophageal invasion was intimately correlated with the level Ⅵ metastasis (P=0.002 and 0.001). Conclusions The most common lymphatic metastasis includes ipsilateral neck Ⅱa, Ⅲ, and Ⅱb, whereas the level Ⅰ and Ⅴ are rarely observed. For PPW-derived tumors, the LMR at the level Ⅶ is up to 60.0%. The incidence of PC or esophageal invasion enhances the risk of level Ⅵ lymph node metastasis. Key words: Hypopharyngeal carcinoma; Lymph node; Clinical target volume