Pattern of Lymph Node Metastases and its Implication in Radiotherapeutic Clinical Target Volume in Patients with Small Cell Carcinoma of the Esophagus

Abstract

<h3>Purpose/Objective(s)</h3> In order to study the pattern of lymph node metastases after esophagectomy of small cell carcinoma of the esophagus (SCCE) and clarify the clinical target volume (CTV) delineation of definite radiotherapy for SCCE. <h3>Materials/Methods</h3> From January 2007 to December 2020, 286 patients with SCCE who had undergone esophagectomy and lymphadenectomy were retrospectively examined from 14 cancer centers in China. The distribution of lymph node metastases was evaluated and the clinicopathologic factors related to lymph node metastasis were analyzed using logistic regression analysis. <h3>Results</h3> 177 patients (61.9%) occurred lymph node metastases in the 286 patients, including 1 positive lymph node (n=58), 2 positive lymph nodes (n=32), 3 positive lymph nodes (n=32) and more than 4 positive lymph nodes (n=55). The mean number of dissected lymph nodes was 17.0, with a rage of 7-60. The incidence of lymph node metastasis was 12.3% (597/4850). The rates of lymph node metastases in patients with upper thoracic tumors were 0% cervical, 32.1% (9/28) upper mediastinal, 7.1% (2/28) middle mediastinal, 0% lower mediastinal, 3.6% (1/28) abdominal, respectively. The rates of lymph node metastases in patients with middle thoracic tumors were 4.3% (6/139), 20.9% (29/139) , 26.6% (37/139) , 2.9% (4/139) , 25.9% (36/139), respectively. The rates of lymph node metastases in patients with lower thoracic tumors were 0%, 12.6% (15/119) , 41.2% (49/119) , 5.0% (6/119) , 47.9% (57/119), respectively. T stage and the length of tumor were the statistically significant risk factors of lymph node metastases of SCCE (<i>P</i><0.05). <h3>Conclusion</h3> To our known, this is a first study about investigating the pattern of lymph node metastases after esophagectomy and guiding the CTV delineation of definite radiotherapy for SCCE. Regardless of tumor location, the upper middle mediastinum is high incidence area of lymph node metastases, abdominal is also high incidence area of lymph node metastases for middle and lower thoracic tumors. The rate of lymph node metastasis of the SCCE increased with the T stage and the length of tumor. These factors and the correlated lymphatic drainage regions should be considered when designing the CTV for Selective regional irradiation of SCCE.