Mediastinal Nodal Involvement After Neoadjuvant Chemoradiation for Siewert II/III Adenocarcinoma

Adenocarcinoma of the gastroesophageal junction (AEG) poses a management challenge, as preoperative prediction of occult mediastinal nodal metastasis is difficult. We sought to identify factors predictive of mediastinal involvement among patients undergoing trimodality therapy.

Patients undergoing trimodality therapy for Siewert II and III AEG at a single institution between 2000 and 2015 were identified. Mediastinal involvement was defined as pathologic nodal involvement after neoadjuvant chemoradiation (ypN+) in mediastinal stations or mediastinal recurrence 2 years or less after resection. Maximal χ² analysis and Youden's J index were used to identify the pretreatment proximal tumor extent that best discriminated mediastinal involvement.

In all, 204 patients (151 [74%] AEG II, 53 [26%] AEG III) were included, of whom 47 (23%) had clinical evidence of thoracic nodal disease. Thirty-one of the 204 patients (15%) met criteria for mediastinal involvement (24 of 31 ypN+, 10 of 31 mediastinal recurrence). Patients with mediastinal involvement had greater proximal tumor extent (median 2 cm [interquartile range, 1.0 to 3.0 cm] vs 1.4 cm [interquartile range, 0.7 to 3.0 cm], P = .030), were more frequently Siewert II lesions (27 of 31 [87.1%] vs 124 of 173 [71.7%], P = .071), and were more often observed to have clinical thoracic nodal metastasis (cN) evidence (13 of 31 [42%] vs 34 of 173 [20%], P = .007) than patients who did not. On multivariable analysis of patients with intrathoracic cN0, esophageal extent of 1.5 cm or greater was independently predictive of mediastinal involvement (odds ratio 5.46, P = .011), whereas Siewert classification was not (Siewert II odds ratio 3.48, P = .116).

Pretreatment proximal tumor extent, rather than Siewert classification, is an independent predictor of mediastinal involvement among AEG II/III patients without clinical evidence of mediastinal metastasis and should be considered during treatment planning.