Endoscopic ultrasound determined maximal tumor thickness is an objective measure of tumor response to chemotherapy in esophageal cancer

Introduction: Endoscopic ultrasound (EUS) plays an important role in staging of tumor depth (T-stage) and regional lymph node involvement (N-stage) in patients with esophageal carcinoma (EC). However, the role of EUS in assessing tumor response to neoadjuvant chemotherapy in surgically resectable EC has not been clearly defined. Methods: As part of a protocol at our institution, patients with EC underwent initial EUS staging followed by two cycles of chemotherapy. A second EUS was performed prior to surgical resection. We reviewed the results of pre-chemotherapy EUS (pre-EUS) and post-chemotherapy EUS (post-EUS) and recorded T and N stages as well as a measurement of maximal tumor thickness. Comparison was made to final pathologic staging. Results: 15 patients with EC had pre- and post-EUS while another 2 patients had only post-EUS prior to surgical resection. Of these 17 patients, all were Caucasian, 16 were male, and mean age was 60.4 years 16 patients had adenocarcinoma and 1 had squamous cell cancer. When compared to final pathology, post-EUS correctly defined the T-stage in 10 patients (accuracy=59%). Of the other 7 patients, post-EUS incorrectly downstaged T-stage in 5 and incorrectly upstaged it in 2. Post-EUS N-staging was correct in 12 patients (accuracy=71%) while it incorrectly downstaged N-stage in 3 patients and incorrectly upstaged it in 2 (these accuracy values compare to our institutional rates of 90% for T-staging and 90% for N-staging in EC patients not receiving chemotherapy prior to resection). When the results of pre-EUS staging were compared to final pathology, the majority of patients (73% T, 60% N) showed no change in tumor stage following chemotherapy. However, tumor thickness decreased significantly (mean pre-EUS= 19.0 mm vs mean post-EUS= 12.1 mm; p< 0.02). When change in maximal tumor thickness was compared to clinical response (dysphagia), no correlation was found. Conclusions: 1. EUS T and N-staging following chemotherapy is inaccurate 2. EUS measured tumor thickness is an objective marker of tumor response to chemotherapy in patients with EC. This marker may provide a more reliable measure of tumor response to chemotherapy than clinical symptoms which rely on subjective measures. 3. Prospective evaluation of EUS determined maximal tumor thickness in relation to clinical response and patient outcome is needed.