O-OGC06 Genomic analysis of response to neoadjuvant chemotherapy in oesophageal adenocarcinoma

Background Oesophageal adenocarcinoma (OAC) is the ninth most common cancer worldwide, with an estimated mortality of over 500,000 deaths yearly. Neoadjuvant chemotherapy (NAC) followed by surgery is the standard of care (SOC) for locally advanced OAC. Although almost all patients receive chemotherapy as SOC, fewer than 20% obtain a clinically meaningful response and benefit before surgery. The OAC genome is complex and heterogeneous between patients, and it is not yet understood whether specific mutational patterns may result in chemotherapy sensitivity or resistance. Methods To identify associations between genomic events and response to NAC in OAC, a comparative genomic analysis was performed in 65 patients using whole-genome sequencing. We defined response to NAC using Mandard Tumour Regression Grade (TRG), with responders classified as TRG1-2 (n = 27) and non-responders classified as TRG4-5 (n = 38). Results We report a higher non-synonymous mutation burden in responders (median 2.08/Mb vs 1.70/Mb, P = 0.036) and elevated copy number variation (CNV) in non-responders (282 vs 136/patient, P<0.001). We identified CNVs unique to each group, with cell cycle (CDKN2A, CCND1), c-Myc (MYC), RTK/PIK3 (KRAS, EGFR) and gastrointestinal differentiation (GATA6) pathway genes being specifically altered in non-responders. Of particular interest was the identification of the Neuron Navigator-3 (NAV3), a known tumour suppressor downstream of EGFR, which was mutated exclusively in non-responders with a frequency of 22%. Conclusions Our work characterises genetic features and mutations that are uniquely associated with response to NAC. We envision a treatment pipeline that incorporates driver mutation profiling in OAC, combining response prediction with targeted therapies to enhance response to NAC and improve survival outcomes.

P-OGC29 Pathological response profiles of FLOT and ECX neoadjuvant chemotherapy in oesophageal adenocarcinoma

Background 70% of patients undergoing neo-adjuvant ECX chemotherapy for adenocarcinoma of the oesophagus, show little to know response in their primary tumour (Mandard 4,5). However, among these patients, those who have a complete nodal response (cN+ to ypN0) have equivalent survival to those with Mandard 1,2,3 tumours. FLOT chemotherapy has shown a survival advantage to ECX, however, rates of primary tumour response and nodal response are yet to be the focus of published study. Methods Retrospective cohort study comparing patients undergoing ECX and FLOT neoadjuvant chemotherapy between 2014 and 2021. Pathological outcomes were examined including, Mandard tumour regression grade (1-5), complete nodal response (cN+ to ypN0), clinically node negative nodal progression (cN0 to ypN+). Results 226 patients had data available for analysis (193 ECX and 33 FLOT). 27% (52/193) of patients receiving ECX showed a response in the primary tumour (Mandard 1,2,3) compared to 63% (21/33) with patients undergoing FLOT (p < 0.001). Complete nodal response rates were 25% in ECX patients and 21% FLOT patients (p = 0.556). Clinically node negative nodal upstaging (cN0 to pN+) was higher among FLOT patients 30% (13/33) than ECX patients 12% (24/193) (p < 0.001). Conclusions FLOT chemotherapy confers improved primary tumour response. However, these findings were not echoed in locoregional nodal responses. Survival advantages with FLOT may result from improved responses in primary tumour and not improved systemic coverage. More data will be needed to explore this and over-come the confounding effect of staging inaccuracies. However, understanding systemic and loco-regional responses of different chemotherapy regimens will be needed to tailor future neoadjuvant treatment regimens.

SP5.1.11 The immune landscape of the Tumour draining lymph node and the Tumour Microenvironment in oesophageal; A novel therapeutic target

Aim The tumour microenvironment (TME) and tumour-draining lymph node microenvironment (LNME) remain poorly understood. Our study profiles the immune, angiogenic and inflammatory environment of the LNME and the TME of oesophagogastric patients. Methods The prognositc value of nodal status, clinical stage and tumour regression grade (TRG) was evaluated using a cohort of OAC patients (n = 702). Immune checkpoints (ICs) on tumour-draining lymph nodes(TDLNs, n = 6) and tumour tissue(n = 9) at surgical resection was assessed by flow cytometry. We also screened for cytokines, angiogenic mediators and chemokines. Using The Cancer Genome Atlas (TCGA), protein and mRNA levels (n = 72) and mutated versus non-mutated copies(n = 87) of this panel was correlated with survival. Results The frequency of CD3+TIM-3 and PD-1+T cells in TDLNs positively correlated with clinical tumour status as did CD8 + PD-1+TIGIT + T cells with nodal burden. Pro-angiogenic factor bFGF was significantly higher within the TME compared with the LNME. PIGF and SAA mediators of tumour growth were significantly higher in the LNME and levels of SAA in LNME positively correlated with adverse features. High levels of pro inflammatory IL-8,IL-6 and Flt1, mutations in pro-inflammatory genes CCL26,IL-31 and IL-17C and anti-tumour IL-1RN and CCL22 correlated with reduced overall survival. Conclusions The TME is more immunosuppressive than the TDLN, however, certain pro-angiogenic factors were enriched in TDLNs suggesting the priming of a pre-metastatic niche. Given the association of ICs with clinical features and tumour biology this may help to inform novel therapeutic approaches.

796 OUTCOMES OF DELAYED SURGERY IN PATIENTS WITH RESIDUAL DISEASE AFTER NEOADJUVANT CHEMORADIOTHERAPY FOR OESOPHAGEAL CANCER

Standard treatment for locally advanced oesophageal cancer is neoadjuvant chemoradiotherapy (nCRT), plus surgery 6-8 weeks later. Time to surgery (TTS) after nCRT seems safe up to 12 weeks, and possibly improves patient condition and pathological response. However, it is unknown whether prolonged TTS is safe in patients with residual disease. The aim of this study was to investigate whether prolonged TTS leads to inferior surgical outcomes and survival in patients with residual disease after nCRT. Methods Patients with pathologically confirmed residual disease 4-6 weeks after nCRT who underwent preoperative PET/CT and surgery were selected from the preSANO-trial and SANO-trial. Patients were stratified by TTS ≤12 weeks versus TTS >12 weeks after completion of nCRT. Primary endpoint was overall survival (OS). Secondary endpoints were progression-free survival (PFS), peroperative unresectability, microscopically radical resections (R0), tumour regression grade (TRG), postoperative complications and risk of distant dissemination. Effects of TTS on OS, PFS and distant dissemination were analysed with Cox regression, adjusted for Charlson comorbidity index (CCI) at baseline, as well as WHO performance score and weight loss after nCRT. Results Forty-two patients were included in the TTS >12 weeks and 132 patients in the TTS ≤12 weeks group. Median follow-up was 20.6 months (IQR 16.1-30.3). Adjusted hazard ratios for OS and PFS were 0.50 (95% CI: 0.24-1.02) and 0.47 (95% CI: 0.25-0.91), respectively, in favour of TTS >12 weeks. Patients with TTS >12 weeks had more postoperative complications (89% vs 72%, p = 0.049), but comparable peroperatively unresectable tumours (11.9% vs. 3.8%, p = 0.11), R0-resections (89% vs 87%, p = 0.89), and TRG-scores (p = 0.97) compared to patients with TTS ≤12 weeks. Patients with TTS >12 weeks showed less distant dissemination (HR 0.40, 95% CI: 0.18-0.88). Conclusion Prolonged TTS beyond 12 weeks in patients with clinically proven residual disease after nCRT did not have a negative effect on OS and on PFS, but was correlated with an increase in postoperative complications. The (non-significantly) better survival outcomes for TTS >12 weeks may be explained by the fact that patients had a lower risk of developing distant dissemination, which may reflect improved selection prior to surgery.

646 PREDICTING RESPONSE TO NEOADJUVANT CHEMOTHERAPY IN PATIENTS WITH OESOPHAGEAL ADENOCARCINOMA

Neoadjuvant chemotherapy is often used prior to surgical resection for oesophageal adenocarcinoma but remains ineffective in a high proportion of patients. The histological Mandard tumour regression grade is used to determine chemoresponse but is not available at the time of treatment decision-making. The aim of this study was to identify factors that predict chemotherapy response prior to surgery. Methods A prospectively collected database of patients undergoing surgical resection for oesophageal adenocarcinoma from a high-volume UK institution was used. Patients were subcategorised using pathological tumour response into ‘responders’ (Mandard grade 1–3) and ‘non-responders’ (Mandard grade 4&5). Multivariable logistic regression analysis was performed to calculate crude and adjusted odds ratios (OR) with 95% confidence intervals (CI) for responder status adjusting for a variety of parameters. Receiver-operator curves (ROC) were calculated. Results Among 315 patients included, 102 (32%) were responders and 213 (68%) non-responders. A decrease in radiological tumour volume (OR 1.92 95%CI 1.02–3.62; p = 0.05), a ‘partial response’ RECIST score (OR 7.16 95%CI 1.49–34.36; p = 0.01), a clinically improved dysphagia score (OR 2.79 95%CI 1.05–7.04; p = 0.04) and lymphovascular invasion (OR 0.06 95%CI 0.02–0.13; p = 0.000) influenced responder status. ROC curve analysis for responder status utilising all available parameters had an area under the curve (AUC) of 0.86. Conclusion This study has highlighted the potential for using pre-defined factors to identify those patients who have responded to neoadjuvant chemotherapy, prior to surgical resection, potentially facilitating a more individualised therapeutic approach.

450 FACTORS AFFECTING CIRCUMFERENTIAL RESECTION MARGIN AFTER ESOPHAGECTOMY AND ITS PROGNOSTIC SIGNIFICANCE-LARGE SINGLE CENTRE EXPERIENCE

The evidence regarding the importance of circumferential resection margin (CRM) as a prognostic factor after esophagectomy is inconclusive in the era of neoadjuvant therapy. We retrospectively analysed our prospectively maintained database for factors that affect CRM positivity, and whether a positive CRM affects event free and overall survival. 2843 patients underwent esophagectomy with curative intent from October 2004 to 2019 at our centre. CRM was analysed as negative, close but technically free (<1 mm) and involved. Methods Data on the following variables was retrospectively extracted from prospective database. CRM status was noted for clinic-radiological T and N stage, level of growth, histology, differentiation grade and neoadjuvant treatment. Intra-operative details such as surgical procedure, approach, surgeon grade, lymphadenectomy and resection status were analysed. On final histopathology; proximal and distal margins, lymph node positivity, lymphovascular invasion(LVI), tumour regression grade(TRG) were analysed. The effect of CRM on development of recurrence and overall survival was evaluated. CRM data was available for 2439 (85.78%) patients. 71.2% of the patients received neoadjuvant chemotherapy. Factors were analysed separately for both close and positive margins. Results 75.8% had negative, 15.6% close and 8.6% positive CRM. Univariately, T stage, adenocarcinoma, poor differentiation, transhiatal approach, R+ resection, positive margins, TRG > 3, LVI and upfront surgery predicted positive CRM. On multivariate, negative CRM was seen in T1/T2 stage [OR 0.325, 95% CI-0.144-0.732, p = 0.007], squamous carcinoma [OR 0.574, 95% CI-0.351-0.958, p = 0.027], R0 resection [OR 0.228, 95% CI-0.086-0.599, p = 0.003] while positive CRM was seen in upfront surgery [OR 2.32, 95% CI-1.55-3.46, p < 0.001], positive nodes [OR 1.748, 95% CI-1.19-2.56, p = 0.004] and LVI [OR 2.73, 95% CI-1.87-3.98, p < 0.001]. Median event-free survival in CRM negative was 64 months compared to 14 months in CRM positive (p < 0.001). Conclusion Positive CRM involvement is a prognostic indicator in patients undergoing esophagectomy and associated with worse event-free and overall survival. CRM-positive disease in esophageal cancer may represent residual tumor, advanced disease, aggressive biology, or poor response to neoadjuvant treatment. All attempts should be made to achieve a clear circumferential resection margin. More evidence is needed to evaluate if adjuvant therapy is justified in these patients and the type of therapy also needs to be determined.

The Prognostic Value of the Lymph Node in Oesophageal Adenocarcinoma; Incorporating Clinicopathological and Immunological Profiling

Response rates to the current gold standards of care for treating oesophageal adenocarcinoma (OAC) remain modest with 15–25% of patients achieving meaningful pathological responses, highlighting the need for novel therapeutic strategies. This study consists of immune, angiogenic, and inflammatory profiling of the tumour microenvironment (TME) and lymph node microenvironment (LNME) in OAC. The prognostic value of nodal involvement and clinicopathological features was compared using a retrospective cohort of OAC patients (n = 702). The expression of inhibitory immune checkpoints by T cells infiltrating tumour-draining lymph nodes (TDLNs) and tumour tissue post-chemo(radio)therapy at surgical resection was assessed by flow cytometry. Nodal metastases is of equal prognostic importance to clinical tumour stage and tumour regression grade (TRG) in OAC. The TME exhibited a greater immuno-suppressive phenotype than the LNME. Our data suggests that blockade of these checkpoints may have a therapeutic rationale for boosting response rates in OAC.

O4 Neural network image capture to predict response of oesophageal adenocarcinoma to neoadjuvant therapy

Introduction Locally advanced oesophageal adenocarcinoma is typically treated with neoadjuvant chemotherapy (NACT) or chemoradiotherapy (NACRT) followed by surgery. Significant benefit to neoadjuvant treatment however is confined to a minority of patients (<25%) and there are no reliable means of establishing prior to treatment in whom this benefit will occur. In this study, we assessed the utility of features extracted from high-resolution digital microscopy of pre-treatment biopsies in predicting response to neoadjuvant therapy in a machine-learning based modelling framework. Method A total of 102 cases were included in the study. Pre-treatment clinical information, including TNM staging, was obtained, along with diagnostic biopsies. Diagnostic biopsies were converted into high-resolution whole slide-images and features extracted using a pre-trained convolutional neural network (Xception). Elastic net regression models were then trained and validated with bootstrapping with 1000 resampled datasets. The response was considered according to Mandard tumour regression grade (TRG). Result There were 45 (44.1%) responders (TRG1-2) and 57 (57%) non-responders (TRG3-5) in the dataset. 34 patients (33.3%) received NACT and 68 (66.7%) received NACRT. A model trained with RNA-seq data achieved fair performance only in predicting response (AUC 0.598 95% CI 0.593–0.603), which was far exceeded by use of segmented diagnostic biopsy images (AUC 0.872 95% CI 0.869–0.875), which also produced well calibrated predictions of risk. Conclusion Despite using a small dataset, impressive performance in classifying response to neoadjuvant treatment can be achieved, particularly using automated image classification. Further study to refine the methodology is required before expansion to clinical settings. Take-home Message Response to neoadjuvant treatment for oesophageal cancer can be predicted from diagnostic biopsies

Real-world data (RWD) reveals benefit for adjuvant chemotherapy with docetaxel, oxaliplatin and fluorouracil/leucovorin (FLOT) is limited to those with tumour regression grade (TRG) ≥3 in oesophago-gastric cancer (OGC).

4039 Background: Despite potentially curative surgery, long-term survival from OGC remains poor due to high relapse rate. Neoadjuvant (naFLOT) and adjuvant (aFLOT) FLOT is currently standard treatment for resectable OGC based on data from the FLOT-4 trial. We explored whether TRG was associated with FLOT-outcome using RWD. Methods: Pts with OGC treated with naFLOT +/- aFLOT at a tertiary UK centre were identified following institutional board approval. Clinical and laboratory data were extracted from the patient record. TRG was evaluated by a histopathologist. Median overall survival (OS) and median progression-free survival (PFS) were evaluated using Kaplan-Meier and Log-rank tests; time taken from start of naFLOT, and associations between factors with Fisher’s exact (FE) test. Results: 171 pts were identified, median FU 30 mths. 144 (84%) male; median age 66 (32-84); oesophagus 66 (38%), junctional (GOJ) 73 (43%), gastric 32 (19%); stage IB 3 (2%), stage IIB 26 (15%), stage III 91 (53%), stage IVA 47 (28%) and unknown 4 (2%). Pts had median of 2 comorbidities (range 0-6); performance status (PS) 0: 95 (56%), PS 1: 71 (41%), PS 2: 3 (2%) and PS unknown 2 (1%). 132/171 pts completed 4 cycles of naFLOT and this was significantly associated with undergoing surgery (p = 0.02). Those who had surgery (140/171) had significantly improved PFS (not reached (NR) vs. 6 mths; 95% CI 2-10; p < 0.001) and OS (NR vs. 12 mths; 95% CI 6-18; p < 0.001). TRG was reported for 126/140 patients who underwent surgery. TRG 1/2 (42/126) vs. TRG ≥3 was significantly associated with improved PFS (NR vs. 35 mths; 95% CI NR; p < 0.001) and OS (median NR either group; p < 0.001). Pts with TRG 1/2 who commenced aFLOT (≥1 cycle; n = 31/42) or completed 4 cycles of aFLOT (17/31) did not have improved PFS or OS vs. those who did not. Those with TRG ≥3 who commenced aFLOT (≥1 cycle; n = 62/85) had improved PFS (median NR vs. 22 mths; 95% CI 13-31 p = 0.006) and OS (median NR vs. 25 mths; 95% CI 18-32 p = 0.019). Those with TRG ≥3 who completed 4 cycles of aFLOT (n = 38/62) had significantly improved PFS (median NR vs. 25 mths; 95% CI 14-36 p = 0.016) and OS (median NR vs. 36 mths; 95% CI 16-55 p = 0.012). There was no difference in PFS or OS in pts with TRG ≥3 who had a dose reduction at any time during aFLOT. Conclusions: TRG is a predictor of outcome following naFLOT + surgery with superior outcomes in those with TRG 1/2. Our analyses suggest that only pts with TRG >3 following naFLOT + surgery benefit from adjuvant FLOT. Prospective randomised studies are required to confirm whether pts with TRG 1/2 require treatment with aFLOT.

Efficacy and safety of camrelizumab combined with FLOT versus FLOT alone as neoadjuvant therapy in patients with resectable locally advanced gastric and gastroesophageal junction adenocarcinoma who received D2 radical gastrectomy.

e16020 Background: Docetaxel-based neoadjuvant chemotherapy has been suggested to be beneficial in patients with locally advanced gastric and gastro-oesophageal junction cancer (GC/GEJC). And immunotherapy also show promising treatment efficacy for advanced GC/GEJC. Here we compared the safety and efficacy of camrelizumab combined with chemotherapy versus chemotherapy alone as the neoadjuvant therapy for patients with resectable locally advanced GC/GEJC. Methods: Eligible patients diagnosed as resectable locally advanced GC/GEJC were randomized to receive neoadjuvant treatment, in arm A, the patients received FLOT alone (docetaxel 50 mg/m²; oxaliplatin 85 mg/m²; leucovorin 200 mg/m²; 5-FU 2600 mg/m², every 2 weeks), in arm B, the patients received FLOT combined with camrelizumab(camrelizumab 200mg intravenously every 3 weeks). Eligible patients underwent gastrectomy with D2 lymph node dissection. The primary end point of this trial was pCR rate and R0 resection rate, and the secondary end points were ORR,PFS, OS and safety profile. Results: From January 15 2020 to January 15 2021, 24 patients were recruited (11 patients in arm A and 13 patients in arm B). 19 patients had completed planned neoadjuvant treatment for 4 cycles (9 pts in the arm A, 10 ptsin the arm B). Two patients in the arm A were waiting for gastrectomy. This analysis was based on the 17 pts. In the arm A, the median age was 61 years (47-72 years) and a total of 5 males and 4 females, ECOG PS 0 (n = 1), ECOG PS 1 (n = 8). In the arm B, the median age was 63 years (57-71 years) and a total of 9 males and 1 females, all patients with ECOG PS 1. The R0 resection rate was high in arm B compared with arm A (10/10,100% vs. 5/7, 71.4%). No pCR were observed in the two arms. Tumour regression grade were as follows:TRG1 [arm A 0% (0/7), arm B 10% (1/10)], TRG2 [arm A 43% (3/7), arm B 60% (6/10)], TRG3 [arm A 29% (2/7), arm B 30% (3/10)].There was a significantly higher proportion of patients achieved a postoperative ypN0 in the arm B than arm A(60% vs 0%), which had preoperative clinical stage cT3-4N+M0. Postoperative pathologic staging was as follows: ypT1 [arm A 14% (1/7); armB 30% (3/10)]. ypT2 [armA 0% (0/7); armB 30% (3/10)]. ypT3 [arm A 29% (2/7); arm B 20% (2/10)]. ypT4 [armA 29% (2/7); armB 20% (2/10)]. Neither serious intraoperative complications nor immune-related adverse events were observed during perioperation. Treatment-related AEs neutropenia and leukopenia were manageable and there was no treatment-related death. Conclusions: Camrelizumab combined with FLOT showed promising efficacy as neoadjuvant treatment for patients with locally advanced gastric or GEJ adenocarcinoma, with low complications and acceptable toxicity. Clinical trial information: ChiCTR2000030610.