OGC SO15 - Utility of radiological re-staging following neo-adjuvant chemotherapy and its impact on oncological outcomes in resectable gastric adenocarcinoma

Abstract Background The current perioperative chemotherapy regimen that comprises the multimodal treatment strategy for gastric cancer consists of Fluorouracil, Leucovorin, Oxaliplatin, and Docetaxel. Despite improvement in outcomes at a population level, real-world data suggests that ≤40% of patients show a poor/no response to the neoadjuvant phase of treatment. Identification of these poor/non-responders may facilitate a re-evaluation of their treatment strategy and prevent potentially futile surgery. Radiological re-staging following neoadjuvant treatment is routinely performed despite its debatable accuracy and benefits. This study aimed to define the accuracy of radiological re-staging and its impact on survival following neoadjuvant treatment for resectable GC. Method Patients with resectable gastric cancer who completed 4 cycles of neoadjuvant FLOT and underwent resectional surgery with curative intent between 2018 and 2022 were retrospectively identified. All patients were clinically staged with gastroscopy, CT and staging laparoscopy. The index radiological/clinical stage at diagnosis was compared to the radiological re-staging following neoadjuvant treatment. Patient were re-staged with either a CT or PET-CT. Both were then compared with the final pathological stage to assess for correlation between the radiological and pathological stage. A survival analysis was then performed to evaluate the impact of radiological-pathological staging discrepancy on overall survival Results A total of 65 consecutive patients met the inclusion criteria of this study. On comparison of the index clinical stage with the radiological re-stage post-neoadjuvant treatment, 71% had concordant stages, 25% were downstaged, and 4% were upstaged. On comparison of the index clinical stage with the final pathological stage, 35% had concordant stages, 38% were upstaged and 27% were down staged (Cohen kappa = -0.224, 95% CI -0.390, -0.058). Discrepancy between clinical stage and radiological re-stage did not influence survival. However, discrepancy between clinical and pathological stage highlighted survival differences where upstaged patients had reduced survival (p = 0.018). Conclusion The accuracy of clinical staging compared to final pathological staging in the setting of aggressive tumour biology remains undefined. Radiological re-staging following neoadjuvant treatment proves to be an unreliable tool for assessing treatment response and does not predict long-term survival outcomes. These findings highlight the importance of accurate staging and the need for more precise methods of evaluating treatment response. This may enhance decision-making, individualise treatment regimens, and improve patient outcomes.