PTH-139 The effect of neo-adjuvant chemotherapy on the discrepancy between the eus and pathological staging of oesophageal cancer

Abstract

Introduction EUS plays an important role in the preoperative staging of oesophageal cancer with high sensitivity and specificity when determining TN stage. However, discrepancy remains between EUS and the pathological TN staging. The majority of patients now undergo neoadjuvant chemotherapy prior to resection which may result in downstaging the tumour if they respond to chemotherapy but may also lead to disease progression if the patient has no response during their 3 months of chemotherapy. We sought to determine whether the patient’s response to chemotherapy correlated with a difference in staging between EUS and pathology. Method A cohort of 107 patients that underwent staging EUS, neoadjuvant chemotherapy, surgical resection and histopathological examination were evaluated. EUS examinations took place at a high volume centre, by 4 different consultants, between July 2011 and July 2014. The patients were grouped according to their tumour regression grade (TRG), with a TRG of 1–3 considered a response to chemotherapy and a TRG of 4–5 considered resistance to chemotherapy. If the difference between EUS and pathology TN stage was greater than 1, the patient was considered to have been over or under-staged. Results Of the 107 EUS examinations, 26 were over-staged and 12 under-staged. Patients with a TRG 1–3 (n = 39), were never under-staged by 2, by either T or N. Eighteen T grades were over-staged: by 2 (n = 9), and by greater than 2 (n = 9). Three N grades were over-staged: this was by 2 (n = 3). Patients with a TRG 4–5 (n = 68) were more frequently under-staged than over-staged. One patient’s T grade was under-staged, by an under-estimation of 2. Eleven N grades were under-staged, this was by 2 (n = 6), and by greater than 2 (n = 5). Two T grades were over-staged, by 2 (n = 2). Four N grades were over-staged: by 2 (n = 3), and by greater than 2 (n = 1). There were 4 incomplete EUS examinations, all within TRG 4–5 group. There was no association between endoscopist and staging accuracy. Conclusion Patients with a TRG 1–3 were never distinctly under-staged, but were over-staged in 50% of cases. This is likely a reflection of the down staging of disease following response to neo-adjuvant chemotherapy. Those patients with a TRG 4–5 had a distinctly different EUS from pathological staging in 25% of cases, and this was twice as frequently under-staging than over staging, potentially reflecting disease progression. In conclusion, response to chemotherapy dramatically affects the perceived accuracy of EUS staging. Disclosure of interest None Declared.