AIM:To examine cytokeratin-18(CK-18) and caspasecleaved CK-18 expression in tumours and correlate with clinicopathological outcomes including tumour regression grade(TRG) response.METHODS:Formalin-fixed human gastro-oesophageal cancers were constructed into tissue microarrays.The first set consisted of 122 gastric/gastro-oesophageal cancer cases not exposed to neoadjuvant chemotherapy and the second set consisted of 97 gastric/gastrooesophageal cancer cases exposed to pre-operative platinum-based chemotherapy.Expression of CK-18 and caspase-cleaved CK-18 was investigated using immunohistochemistry.RESULTS:CK18 was commonly expressed in gastrooesophageal tumours(92.6%).Fifty-six point seven percent of tumours previously exposed to neoadjuvant chemotherapy were positive for caspase-cleaved CK-18 expression compared to only 24.6% of tumours not previously exposed to neoadjuvant chemotherapy(P = 0.009).In patients who received neoadjuvant chemotherapy,caspase-cleaved cytokeratin-18 expression correlated with favourable TRG response(TRG 1,2 or 3,P = 0.043).CONCLUSION:This is the largest study to date of CK-18 and caspase-cleaved CK-18 expression in gastrooesophageal tumours.We provide the first evidence that caspase-cleaved CK-18 predicts tumour regression with neoadjuvant chemotherapy. AIM: To examine cytokeratin-18 (CK-18) and caspasecleaved CK-18 expression in tumors and correlate with clinicopathological outcomes including tumor regression grade (TRG) response. METHODS: Formalin-fixed human gastro-oesophageal cancers were constructed into tissue microarrays. The first set consisted of 122 gastric / gastro-oesophageal cancer cases not exposed to neoadjuvant chemotherapy and the second set consisted of 97 gastric / gastrooesophageal cancer cases exposed to pre-operative platinum-based chemotherapy. Expression of CK-18 and caspase-cleaved CK -18 was investigated using immunohistochemistry .RESULTS: CK18 was commonly expressed in gastrooesophageal tumors (92.6%). Fifty-six point seven percent of patients previously exposed to neoadjuvant chemotherapy were positive for caspase-cleaved CK-18 expression compared to only 24.6% of tumours not previously exposed to neoadjuvant chemotherapy (P = 0.009). In patients who received neoadjuvant chemotherapy, caspase-cleaved cytokeratin-18 express CONCLUSION: This is the largest study to date of CK-18 and caspase-cleaved CK-18 expression in gastrooesophageal tumors. We provide the first evidence that caspase-cleaved CK-18 predicts tumor regression with neoadjuvant chemotherapy.