Advanced Gastroesophageal Cancer Research Articles

Multiomics reveals tumor microenvironment remodeling in locally advanced gastric and gastroesophageal junction cancer following neoadjuvant immunotherapy and chemotherapy

BackgroundPerioperative chemotherapy is the standard of care for patients with locally advanced gastric and gastroesophageal junction cancer. Recent evidence demonstrated the addition of programmed cell death protein 1 (PD-1) inhibitors...

Abstract A049: Peritoneal tumor DNA as a prognostic biomarker in locally advanced gastroesophageal cancer: A pilot prospective cohort study

Abstract Background: Gastroesophageal cancers commonly spread to the peritoneum. Peritoneal disease significantly alters patient prognosis and treatment-intent. Currently, peritoneal lavage cytology (PLC) is the method of choice for detecting peritoneal micro-metastasis within the peritoneum. Despite its pervasive use, PLC has a variable sensitivity of 10% - 80% in detecting peritoneal micro-metastasis in gastroesophageal cancers. Peritoneal tumor DNA (ptDNA) is tumor-derived DNA detectable in peritoneal lavage fluid. ptDNA-positivity may indicate peritoneal micro- metastasis and may be more sensitive than PLC in staging the peritoneum and predicting disease- free survival (DFS) and overall survival (OS). We aimed to develop and test a tumor-informed platform for ptDNA detection and validate its sensitivity and specificity against PLC. Methods: For this pilot study, peritoneal lavage fluid were collected at staging laparoscopy from 15 patients with gastroesophageal cancer. Cytology and peritoneal metastases (where clinically detectable) were confirmed by histopathology. A tumor-informed ptDNA testing was performed via whole-genome sequencing of tumor tissue and buffy coat to identify somatic variants for each patients, followed by tracking of up to 96 variants in each patient’s peritoneal fluid. Results: 5 out of 15 patients were either cytology positive or had macroscopic peritoneal disease and ptDNA was detectable in all 5 cases. Additionally, out of the 10 cytology-negative patients without macroscopic peritoneal disease, ptDNA positivity was detected in 6 patients prior to commencing neoadjuvant chemotherapy or surgery. Two of these 6 patients demonstrated radiological evidence of recurrence at 15- and 18-months follow-up respectively. Interestingly, one patient with macroscopic peritoneal disease tested negative for cytology. In this case, peritoneal lavage was carried out to the upper two abdominal quadrants only, and the pelvic deposit of disease was detected after the lavage had been completed. Despite a negative cytology result, ptDNA was detected using the same fluid sample, suggesting a higher sensitivity compared to PLC. Conclusions: This pilot study demonstrates that a tumor-informed ptDNA detection platform is feasible and potentially more sensitive than PLC in gastroesophageal cancer. To further validate the clinical utility of ptDNA we are proceeding to a multi-center prospective cohort study. Citation Format: Zexi Allan, Yuxuan Wang, Jeanne Tie, Niall Tebbutt, Nicholas Clemons, Nickolas Papadopoulos, Kenneth Kinzler, Bert Vogelstein, David SH Liu. Peritoneal tumor DNA as a prognostic biomarker in locally advanced gastroesophageal cancer: A pilot prospective cohort study [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A049.

Ramucirumab plus paclitaxel as switch maintenance versus continuation of first-line oxaliplatin-based chemotherapy in patients with advanced HER2-negative gastric or gastro-oesophageal junction cancer (ARMANI): a randomised, open-label, multicentre, phase 3 trial.

Paclitaxel plus ramucirumab is recommended as a second-line treatment regimen in patients with advanced HER2-negative gastric or gastro-oesophageal junction cancer. We aimed to assess whether switch maintenance or early second-line therapy with paclitaxel plus ramucirumab improved outcomes compared with continuation of oxaliplatin and fluoropyrimidine doublet chemotherapy as a first-line strategy. ARMANI was a multicentre, open-label, randomised, phase 3 trial done in 31 hospitals in Italy. We enrolled patients aged 18 years or older with an Eastern Cooperative Oncology Group performance status of 0 or 1 and locally advanced unresectable or metastatic HER2-negative gastric or gastro-oesophageal junction cancer, who had disease control after 3 months of FOLFOX (leucovorin, fluorouracil, and oxaliplatin) or CAPOX (capecitabine and oxaliplatin). Patients were randomly assigned (1:1) to either paclitaxel 80 mg/m2 on days 1, 8, and 15 plus ramucirumab at 8 mg/kg on days 1 and 15 every 28 days intravenously (switch maintenance group) or continuation of oxaliplatin-based doublet chemotherapy (FOLFOX or CAPOX) for an additional 12 weeks, followed by fluoropyrimidine monotherapy maintenance (control group). Randomisation was stratified by previous gastrectomy (no vs yes), peritoneal carcinomatosis (yes vs no), and primary tumour location (gastro-oesophageal junction vs gastric). Treatment group allocation was done using a web-based system with a minimisation algorithm implementing a random component. The primary endpoint was progression-free survival, analysed on an intention-to-treat basis. The safety population included patients who received at least one dose of the study treatment. This study is registered with ClinicalTrials.gov, NCT02934464, and is complete. Between Jan 1, 2017, and Oct 2, 2023, 280 patients were randomly assigned to receive paclitaxel plus ramucirumab (switch maintenance group; n=144) or to continue FOLFOX or CAPOX (control group; n=136). All patients were White. 180 (64%) of 280 patients were male and 100 (36%) were female. At a median follow-up of 43·7 months (IQR 24·0-57·9), 253 (90%) of 280 patients had a progression-free survival event: 131 (91%) of 144 patients in the switch maintenance group and 122 (90%) of 136 patients in the control group. Median progression-free survival was 6·6 months (95% CI 5·9-7·8) in the switch maintenance group and 3·5 months (2·8-4·2) in the control group (HR 0·61, 95% CI 0·48-0·79; p=0·0002). The assumption of proportional hazards was violated; in an analysis of 24-month restricted mean survival time, restricted mean progression-free survival was 8·8 months (95% CI 7·7-9·9) in the switch maintenance group and 6·1 months (5·0-7·2) in the control group (p=0·0010). The most frequent grade 3-4 treatment-related adverse events were neutropenia (37 [26%] patients in the switch maintenance group vs 13 [10%] patients in the control group), peripheral neuropathy (eight [6%] vs nine [7%]) and arterial hypertension (nine [6%] vs none). Serious adverse events occurred in 28 (20%) of 141 patients in the experimental group and 15 (11%) of 135 patients in the control group; these events were treatment-related in two (1%) patients in the switch maintenance group (pulmonary embolism) and two (1%) patients in the control group (mucositis and anaemia). No treatment-related deaths occurred. Paclitaxel and ramucirumab switch maintenance could be a potential treatment strategy in patients with advanced HER2-negative gastric or gastro-oesophageal junction cancer who are not eligible for immunotherapy or targeted agents. Partly funded by Eli Lilly.

Cost-effectiveness analysis of first-line sintilimab plus chemotherapy vs. chemotherapy alone for unresectable advanced or metastatic gastric or gastroesophageal junction cancer in China.

The Chinese Society of Clinical Oncology (CSCO) has recommended sintilimab plus chemotherapy (SINT + Chemo) as a standard first-line therapy for advanced gastric cancer or gastroesophageal junction cancer (GC/GEJC), based on the proven effectiveness and safety in the ORINT-16 trail. Its cost-effectiveness, however, remains to be evaluated. We established a partitioned survival approach (PartSA) model with a 10-year time horizon to determine whether SINT + Chemo (vs. chemotherapy) was more cost-effective as a first-line treatment for unresectable advanced or metastatic GC/GEJC. Survival data was generated from the ORIENT-16 trail. Cost calculation was limited to direct medical costs. Database of Hunan Public Resources Trading Service Platform was used as the source for obtaining drug prices. Other cost and utility values were gathered from established literature. Incremental cost-effectiveness ratio (ICER) was the primary output. Additionally, we conducted sensitivity analysis, subgroup analysis, and scenario analysis. In the base-case analysis, group SINT + Chemo showed an increase in utility value by 0.32 quality-adjusted life-years (QALYs) at an extra cost of $7988.43, resulting in an ICER of $25239.29/QALY, below the Chinese cost-effective willingness-to-pay (WTP) threshold of $38223.34. Upon further subgroup analysis according to patients' programmed death 1 ligand (PD-L1) combined positive score (CPS), the ICERs were $26341.01/QALY for patients highly expressing PD-L1 (CPS ≥5) and $17658.26/QALY for patients lowly expressing PD-L1 (CPS <5). Based on the sensitivity analysis, we found the PFS utility was the parameter that had the most significant impact on the model's outcomes. Moreover, in scenario analysis, the results remained consistent despite variations in the model's time frame. In China, SINT + Chemo is a more cost-effective option (vs. chemotherapy) as a first-line therapy for unresectable advanced or metastatic GC/GEJC, irrespective of PD-L1 expression levels.

785. MANAGEMENT OF ESOPHAGEAL CANCER WITH CONCURRENT CERVICAL NODE METASTASIS: A NATIONWIDE POPULATION-BASED COHORT STUDY

Abstract Background In the Netherlands, the standard treatment of locally advanced, resectable esophageal cancer without metastasis is neoadjuvant chemoradiotherapy followed by esophagectomy. There is a small subset of patients that present with concurrent cervical lymph node metastasis (LNM). Historically this was seen as distant metastasis and surgical intervention has usually not been an option for these patients. The contemporary TNM classification now categorizes these lymph node stations as locoregional disease. Our current study aims to describe current treatment paradigms in the Netherlands for patients presenting with esophageal cancer and concurrent cervical LNM. Methods This population-based cohort study utilized data from the Netherlands Cancer Registry (NCR), encompassing patients with locally advanced thoracic esophageal or gastroesophageal junction cancer and concurrent cervical lymph node metastasis. Treatment modalities were categorized into five options: neoadjuvant therapy followed by surgery (Neo + S), definitive chemoradiotherapy (dCRT), chemotherapy with or without radiotherapy &amp;lt; 30 Gray (CT), radiotherapy (RT), and best supportive care (BSC). Overall survival (OS) was assessed using the Kaplan-Meier method and compared via the log-rank test. Hazard rates were computed using Cox proportional hazards regression, with adjustment for confounding achieved through inverse probability of treatment weighting (IPTW). Results Between 2015 and 2021, a cohort of 412 patients was identified from the NCR database. Median survival durations were observed as follows: 24.2 months for Neo + S, 18.0 months for dCRT, 14.5 months for CT, 7.0 months for RT, and 3.2 months for BSC (Figure). A comparison between the Neo + S group and dCRT demonstrated a significant improvement in survival (p=0.02). Further subdivision of the surgical group into neoadjuvant CRT or chemotherapy did not reveal a significant difference in survival (p=0.6). Utilizing IPTW to adjust for confounding factors, Neo + S maintained its survival advantage. Conclusion The retrospective cohort findings suggest that neoadjuvant therapy followed by surgery may represent the optimal approach for managing esophageal cancer patients with cervical LNMs Yet, it's vital to recognize the influence of confounding by indication, which statistical adjustments may not entirely rectify. Furthermore, immortal time bias notably skews results favorably toward surgery. Nevertheless, the results emphasize the importance of considering surgery as a viable option for these patients. These limitations underscore the critical need for a prospective study, prompting the launch of the NODE-II trial.

1420P Fibroblast growth factor receptor 2 isoform IIIb (FGFR2b) protein overexpression and biomarker overlap in patients with advanced gastric or gastroesophageal junction cancer (GC/GEJC)

1420P Fibroblast growth factor receptor 2 isoform IIIb (FGFR2b) protein overexpression and biomarker overlap in patients with advanced gastric or gastroesophageal junction cancer (GC/GEJC)

From guidelines to radiology practice: navigating the 2023 ASCO guidelines for advanced gastroesophageal cancer and beyond.

The American Society of Clinical Oncology (ASCO) updated the guidelines for the treatment of advanced gastroesophageal (GE) cancer in 2023, signifying a major shift towards targeted therapeutics and precision medicine. This article serves as an imaging-based review of recent developments in the care of patients with GE cancer. We cover the epidemiology, the developing treatment paradigms, and the imaging assessment of GE malignancy. In addition, this review aims to familiarize radiologists with the unique adverse effects pertaining to therapeutics, surgeries, radiation therapies, and associated imaging corollaries. A case-based approach will be used to both explore the efficacy of modern treatments and demonstrate their adverse effects, such as chemotherapy-associated pneumonitis, radiation esophagitis, and anastomotic failure. With this comprehensive exploration of gastroesophageal cancer, radiologists will be equipped with the essential tools to inform the treatment decisions made by medical oncologists, radiation oncologists, and surgical oncologists in the new era of precision medicine.

Pembrolizumab in combination with trastuzumab for treatment of HER2-positive advanced gastric or gastro-esophageal junction cancer.

Gastric cancer remains a challenging malignancy with a high global mortality rate. Recent advances in targeted therapy and immunotherapy have shown promise in improving patient outcomes. This paper reviews the impact of incorporating targeted agents such as trastuzumab and immunotherapeutic agents like pembrolizumab into standard chemotherapy regimens for gastric cancer treatment. A comprehensive analysis was conducted on pivotal clinical trials, including KEYNOTE-590, KEYNOTE-811, and ToGA, focusing on their methodologies, patient populations, treatment regimens, and outcome measures. The review also explored emerging research avenues in precision medicine, particularly genomic sequencing and biomarker identification. To assess the efficacy and survival benefits of adding trastuzumab and pembrolizumab to standard chemotherapy in the treatment of gastric cancer and to outline future directions in gastric cancer research. Including trastuzumab and pembrolizumab in treatment regimens for human epidermal growth factor receptor 2 (HER2)-positive and PD-L1-expressing gastric cancers significantly improved progression-free and overall survival rates compared to chemotherapy alone. These findings highlight the potential of personalized therapy in enhancing treatment outcomes. Furthermore, ongoing research into the gastric cancer microenvironment and the role of the microbiome suggests novel targets for future therapeutic interventions. The integration of targeted and immunotherapeutic agents with traditional chemotherapy represents a pivotal shift in gastric cancer treatment, moving towards more personalized and effective regimens.

Cost-effectiveness analysis of pembrolizumab plus chemotherapy versus placebo plus chemotherapy for HER2-negative advanced gastric/gastroesophageal junction cancer in the Chinese healthcare system

ABSTRACT Background This study compares first-line pembrolizumab plus chemotherapy with chemotherapy alone for patients with HER2-negative advanced gastric cancer (GC) and gastroesophageal junction cancer (GEJC) in China. Methods A Markov state-transition model was developed based on the phase 3 randomized KEYNOTE-859 clinical trial data. The health state utility values and direct medical costs were derived from the KEYNOTE-859 clinical trial, the relevant literature, and local charges. The measured outcomes included quality-adjusted life-years (QALYs) and the incremental cost-effectiveness ratio (ICER). Probabilistic and one-way sensitivity analyses (OWSA) were performed to assess the uncertainty of the model. Results In the base analysis, the incremental effectiveness and cost of pembrolizumab plus chemotherapy versus chemotherapy alone were 0.22 QALYs and $16,627.31, respectively, resulting in an ICER of $76,936.60/QALY, which is higher than the willingness-to-pay threshold in China ($35,864.61/QALY). Subgroup analyses revealed that the ICERs of pembrolizumab plus chemotherapy versus chemotherapy alone were $72,762.68 and $34,813.70 in the populations with PD-L1 CPS of 1 or higher (CPS ≥ 1) and PD-L1 CPS ≥ 10 (CPS ≥ 10), respectively. Conclusions As first-line therapy for patients with locally advanced or metastatic HER2-negative GC/GEJC in China, pembrolizumab plus chemotherapy is less cost-effective than chemotherapy alone, however, in the CPS ≥ 10 subgroup is more.

Molecular SPECT/CT Profiling of Claudin18.2 Expression In Vivo: Implication for Patients with Gastric Cancer.

Zolbetuximab (IMAB362), a monoclonal antibody targeting Claudin18.2 (CLDN 18.2), demonstrates a significant clinical benefit in patients with advanced gastroesophageal cancers. The noninvasive assessment of CLDN18.2 expression through molecular imaging offers a potential avenue for expedited monitoring and the stratification of patients into risk groups. This study elucidates that CLDN18.2 is expressed at a noteworthy frequency in primary gastric cancers and their metastases. The iodogen method was employed to label IMAB362 with 123I/131I. The results demonstrated the efficient and reproducible synthesis of 123I-IMAB362, with a specific binding affinity to CLDN18.2. Immuno-single-photon emission computed tomography (SPECT) imaging revealed the rapid accumulation of 123I-IMAB362 in gastric cancer xenografts at 12 h, remaining stable for 3 days in patient-derived tumor xenograft models. Additionally, tracer uptake of 123I-IMAB362 in MKN45 cells surpassed that in MKN28 cells at each time point, with tumor uptake correlating significantly with CLDN18.2 expression levels. Positron emission tomography/computed tomography imaging indicated that tumor uptake of 18F-FDG and the functional/viable tumor volume in the 131I-IMAB362 group were significantly lower than those in the 123I-IMAB362 group on day 7. In conclusion, 123I-IMAB362 immuno-SPECT imaging offers an effective method for direct, noninvasive, and whole-body quantitative assessment of tumor CLDN18.2 expression in vivo. This approach holds promise for accelerating the monitoring and stratification of patients with gastric cancer.

Cost-effectiveness of tislelizumab plus chemotherapy vs chemotherapy as first-line treatment of PD-L1 positive advanced gastric or gastroesophageal junction adenocarcinoma from a Chinese perspective

ABSTRACT Background This work was designed to assess the cost-effectiveness of front-line tislelizumab plus chemotherapy (TIS+Chemo) in advanced gastric cancer (GC) or gastroesophageal junction cancer (GEJC) with positive expression of programmed cell death ligand 1 (PD-L1) from the perspective of Chinese healthcare system. Research design and methods A 10-year partitioned survival model was undertaken utilizing clinical data from RATIONALE 305. Costs and utilities were both discounted at an annual rate of 5%. The primary outcome was incremental cost-effectiveness ratios (ICERs) and calculated as the cost per quality-adjusted life years (QALYs). The willingness-to-pay (WTP) threshold was set as $18,625/QALY. Only direct medical costs were considered. Sensitivity analyses and subgroup analyses were performed to evaluate the robustness of the model. Results In the base-case analysis, the incremental cost and effectiveness associated with TIS+Chemo vs Chemo was 7,361 and 0.38 QALYs, respectively, leading to an ICER of 19,371/QALY. At the WTP threshold of $18,625/QALY, the TIS+Chemo was not a cost-effective first-line treatment option. The model outcomes were robust. Conclusions TIS+Chemo did not provide a cost-effective approach for PD-L1 positive advanced GC/GEJC in China setting. However, TIS+Chemo might be cost-effective in provinces with higher WTP threshold. Clinical trial registration RATIONALE 305, www.clinicaltrials.gov, identifier is NCT03777657.

Use of artificial intelligence–based digital pathology to predict outcomes for immune checkpoint inhibitor therapy in advanced gastro-esophageal cancer.

4013 Background: Accurate prediction of response and survival outcomes with anti-PD-1/PD-L1 immune checkpoint inhibition (ICI) remains a significant challenge in gastro-esophageal cancers. In this study, we use an artificial intelligence (AI)-based single-cell analysis of digitized whole-slide H&amp;E images (WSIs) to predict objective response and survival benefit of ICI in two independent cohorts of gastro-esophageal cancer patients. Methods: WSIs were obtained from 82 ICI-treated advanced gastroesophageal cancer patients (gastric, esophageal, and gastro-esophageal junction adenocarcinoma and squamous cell carcinoma) at Stanford University for discovery, and 189 ICI-treated advanced gastric adenocarcinoma patients at Southern Medical University for external validation. Deep learning models were deployed for automated tumor area detection and segmentation of cell nuclei within WSIs. We developed a fully automated cell annotation approach by leveraging multiplex immunofluorescence and trained a deep learning model to classify nuclei into four cell types from H&amp;E (tumor cells, lymphocytes, neutrophils, and macrophages). A total of 66 features were computed to quantify cell composition and cell-cell interactions within the tumor microenvironment. Treatment outcomes were assessed using progression-free survival (PFS) and best objective response per the Response Evaluation Criteria in Solid Tumors (v1.1), with statistical significance reported at the 95% confidence level. Results: In the training cohort, a spatial feature characterizing lymphocyte and neutrophil interaction had the strongest association with PFS (hazard ratio = 0.44, 95% CI 0.24-0.79, P = 0.0046). In the validation cohort, the spatial biomarker positive population had significantly improved PFS compared to the spatial biomarker negative population (hazard ratio = 0.41, 95% CI 0.27-0.61, P &lt; 0.0001; median time to event: 19 months vs 9 months). For predicting objective response in the validation cohort, a multivariate model combining the spatial features achieved AUROC = 0.81 compared to AUROC = 0.65 for PD-L1 CPS (P = 0.0014), while combining the multivariate model with PD-L1 CPS achieved AUROC = 0.84. Conclusions: A single-cell computational pathology approachidentifies spatial biomarkers with predictive utility for determining ICI treatment outcomes in advanced gastro-esophageal cancer. Further validation of these findings is being pursued in additional cohorts.

Preoperative nivolumab plus SOX in patients with locally advanced gastric or gastro-esophageal junction cancer: A phase 2, single-arm trial.

4074 Background: Preoperative chemotherapy has been widely recommended in patients with locally advanced gastric or gastro-esophageal junction cancer (GC/GEJC), and the addition of programmed cell death 1 (PD-1) inhibitor is under investigation. We conducted a single-arm phase II trial (Stimulate-01) to evaluate the efficacy and safe of the anti-PD-1 antibody nivolumab plus SOX regimen in patients with locally advanced GC/GEJC and to explore the biomarker associated with therapy response. Methods: Patients with locally advanced GC/GEJC (cT3-4N+M0) were enrolled and received either 3 preoperative and 3 postoperative cycles of nivolumab (360 mg, IV, d1, Q21d) plus SOX regimen (oxaliplatin 130 mg/m2, IV, d1 with oral S-1 40-60mg, bid, d1-d14, Q21d) therapy, followed by 11 cycles of nivolumab monotherapy. The primary endpoint was the pathological complete response (pCR) rate, while the major pathological response rate (mPR), 3-year-DFS and 3-year-OS as the second endpoint. This clinical trial was registered at Clinicaltrial.gov (NCT05739045). In addition, tissue sample before and after treatment from patients were performed scRNA-seq. Results: Forty-six patients were enrolled from November 2022 to March 2023, with a median age of 66 years (range, 34-74), and 38 were male. The pCR rate was 28.26% [95% confidence interval (CI), 15.2%-41.3%], and the major pathologic response (mPR) [tumor regression grade (TRG)0/1] rate was 41.3% (95% CI, 27.1%-55.5%). All the patients underwent R0 resection. The mPR rate in patients with PD-L1 CPS ≥5 and patients with PD-L1 CPS&lt;5 was 42.86% vs 38.89% ( P= 0.790). In addition, This clinical study period spans from epidemic control to full liberalization in China. The mPR rate in patients infected with COVID-19 was 44.44% (12/27), while the mPR rate in patients who have not been infected with COVID-19 was 36.84% (7/19) ( P=0.146). There were no severe complications or death related to the surgery. The scRNA-seq data revealed that the composition of MHC-II (HLA-DRA, HLA-DPA1, HLA-DRB1, HLA-DPB1 and HLA-DQB1) were significantly over-expressed in cancer cell of treatment-sensitive patients (TRG0/1) compared to that of treatment-insensitive patients (TRG2/3). Then the MHC-II expression in pre-treatment biopsy samples from 240 GC patients who received preoperative immunotherapy plus chemotherapy were performed by immunohistochemistry. The results showed that the mPR rate in patients with MHC-II IHC ≥2 and patients with MHC-II IHC&lt;2 was 58.87% (83/141) vs 21.21% (21/99) ( P&lt;0.001). Conclusions: Nivolumab plus SOX as neoadjuvant therapy showed an encouraging pCR rate, mPR rate, and manageable safety. The long-term efficacy of this combination of regimens will be continued to follow up. In addition, the MHC-II expression may be a potential biomarker for predicting the effectiveness of immunotherapy combined with chemotherapy for GC/GEJC. Clinical trial information: NCT05739045 .

Exploration of neoadjuvant chemotherapy and post-tumor microenvironment for advanced gastric cancer (GC) or gastroesophageal junction cancer (EGJ).

e16099 Background: Neoadjuvant chemotherapy (NAC) is still the main strategy for operable local advanced gastric cancer (GC) or gastroesophageal junction cancer (EGJ). Keynote585 and Matterhorn studies had demonstrated the improvement of pathologic complete response rate (PCR), however, the overall survival benefit remains unclear. Little is known why patients’ response differently to NAC in terms of chemotherapy regiment and post neoadjuvant tumor microenvironment (TME). Methods: We retrospectively analyzed the resectable GC or EGJ patients who had been treated with neoadjuvant chemotherapy followed by surgery during 2019.11.26-2023.8.18 in the Chinese PLA general hospital. Patients with complete survival data were enrolled in the final evaluation. The association between clinical features or chemotherapy regiment and outcomes including TGR grade (NCCN criteria) and survival data were explored. Furthermore, tumor-microenvironment by means of multiplex fluorescence staining(mIHC) (CD8, CD68, CD56, PD1, PDL1, PANCK) after SOX neoadjuvant chemotherapy was analyzed. Results: 184 patients were offered neoadjuvant chemotherapy and underwent surgery. Due to follow-up lost, 141 patients with complete survival data were included in this analysis finally. Average age was 61, majority of patients were male. 85 patients received Sox and 33 received Xelox and 12 patients with docetaxel and S1(DS) and 11 patients were administered with triplets (FOLT and DOS). The median cycle of neoadjuvant treatment was 4(range from 1-7). Large proportion of patients were performed Laparoscopic. 31 patients suffered from post surgery complication. Above all, 1-year DFS and 2-year DFS, 3-year DFS rate were 72.6%, 54.8%, 49.0% respectively. 2-year OS and 3-year OS rate were 76.9%, 64.5%. PCR rate was 6.38% (n=9), which is consistent with other previous studies. 9 patients achieved TRG 0 and 26 had TRG 1. There is no statistical difference between triplets and double regiment of NEC for TRG0-1 group (45.5% vs 23.1%, p=0.099). The addition of docetaxel to oxaliplatin based therapy had not improved the TRG0-1 population compared with docetaxel-free regiment (30.4% VS 23.7%, p=0.496). YN0 is a predictor of longer survival in contrast YN+( 1-year DFS, 89.4% vs 62.8%, p=0.000).In the mIHC analyses, the density of CD8 positive and CD8+PD1- in the TGR0-1 group is higher than those cells in the TGR 2-3 group(P&lt;0.05). TGR0-1 group had lower density of PDL1+,CD68+PDL1+ and CD68+PDL1- cells in contrast to TGR 2-3 group(P&lt;0.05).Other multi-dimensional analyses were ongoing to be further disclosure. Conclusions: Neoadjuvant chemotherapy led to nearly 7% PCR rate for patients with local advanced GC. YN0 after NAC is a predictor of longer survival. CD8 positive and CD8+PD1- might be the determinant immune cells for better anticancer-response when exposed to chemotherapy.

Influence of neoadjuvant regimen on the prognosis of locally advanced gastric and gastroesophageal junction cancer with HER2 overexpression.

e16082 Background: The relative high recurrence rate in locally advanced gastric or gastroesophageal junction (G/GEJ) cancer with Her2 overexpression after surgery, along with the absence of a standard neoadjuvant treatment protocol, necessitates exploration of novel approaches for this patient population. Methods: In this study, we conducted a retrospective analysis of clinical characteristics, postoperative pathological results, and survival data for patients who underwent neoadjuvant treatment and subsequent surgery at our center from September 2020 to December 31, 2022. The inclusion criteria were as follows: 1) pathologically confirmed adenocarcinoma of the G/GEJ; 2) diagnosed as cT3-4 or N+ by enhanced CT and endoscopic ultrasound; 3) Her2 immunohistochemistry 3+ or 2+ with Fish positive in biopsy specimens; 4) discussed in a multidisciplinary team for the need for neoadjuvant treatment; 5) received 2-4 cycles of neoadjuvant therapy; 6) underwent radical D2 surgery; 7) had complete follow-up data. Results: Seventy-three patients met the inclusion criteria, with 19 receiving chemotherapy + anti-PD-1, 10 receiving chemotherapy + anti-Her2, and 44 receiving chemotherapy alone. Their pCR rates were 31.6%, 10%, and 2.3%, respectively (P = 0.003); MPR rates were 42.1%, 30%, and 11.4% (P = 0.022). As of the last follow-up on December 31, 2023, the median DFS for the chemotherapy group was 18.1 months (95% confidence interval 14.9-21.3); median DFS for the other two groups had not been reached. DFS analysis revealed differences in median DFS among different neoadjuvant treatment regimens (P = 0.025); further pairwise comparisons indicated that this difference mainly stemmed from the chemotherapy + anti-Her2 group compared to the chemotherapy group. Conclusions: In locally advanced gastric and gastroesophageal junction cancer with Her2 overexpression, neoadjuvant chemotherapy combined with anti-Her2 treatment improves the pCR rate and prolongs DFS compared to neoadjuvant chemotherapy alone.

Neoadjuvant therapy using PD-1 inhibitor plus chemotherapy with different intervals between chemotherapy cycles for locally advanced gastric or gastroesophageal junction cancer: A randomized phase 2 study.

4064 Background: To explore the influence of reducing dose-intensity of chemotherapeutic agents by prolonging the interval of chemotherapeutic cycles on clinical efficacy, especially when combined with immune checkpoint inhibitors, we conducted a single-center, prospective, randomized, phase II exploratory study in patients with locally advanced gastric or gastroesophageal junction (G/GEJ) cancer. Methods: Patients were randomly assigned to receive either toripalimab plus FLOT regimen for four biweekly cycles or three triweekly cycles before the operation. The primary endpoint was pathological complete response (pCR) rate, the secondary endpoints were major pathological response (MPR) rate, event-free survival (EFS), and safety. Results: 70 patients were enrolled; of these, 69 were eligible for inclusion. The overall pCR rate was 26.1% and the MPR rate was 55.1%. There were no statistical differences in pCR rates and MPR rates between the two groups. Although no statistical differences were found among the subgroups, the pCR rate for patients with PD-L1 CPS ≥1 was 42.1% (8/19) while 6.7% (1/15) for PD-L1 CPS&lt;1 in the triweekly group ( P=0.047). Analysis of lymphocyte subsets in peripheral blood showed that CD3+CD8+PD-1+Ki-67+ T lymphocyte absolute counts were elevated in triweekly group and reduced in biweekly group before the second and third cycle of therapy. The incidence rates of pyrexia and myelosuppression in the biweekly group were higher than those in the triweekly group. Conclusions: These data support the idea that the efficacy of toripalimab plus FLOT, given triweekly for three cycles, was not inferior to its administration biweekly for four cycles in locally advanced G/GEJ cancer. The finding is particularly significant for those with PD-L1 CPS ≥1 and warrants further validation. Clinical trial information: NCT04891016 .

Classification of HER2 status across multiple cancers using epigenomic profiles from a novel liquid biopsy assay.

3047 Background: The efficacy of trastuzumab deruxtecan in multiple cancers led to a recent FDA granting of priority review for the treatment of adults with HER2-positive solid tumors. This underscores the critical need for reliable assessment of HER2 expression across cancers. The current standard using IHC/ISH for HER2 scoring is fraught with challenges including scoring discordance and tumor heterogeneity. Here we describe the ability to classify HER2 status from 1 ml of plasma, using epigenomic signatures from a novel multi-analyte liquid biopsy (LBx) platform, offering a minimally invasive approach for patient (pt) selection across cancers. Methods: We selected 179 samples from 172 pts with advanced breast (BC), gastro-esophageal (GEA) and ovarian (OV) cancers who had associated HER2 status scored from tissue-based IHC/ISH according to ASCO/CAP guidelines (table). Samples were taken at baseline or at progression and those with detectable cell free DNA, as assessed by iChorCNA, were profiled for genome-wide epigenomic signals across histone modifications associated with active enhancers, promoters and DNA methylation. A regularized regression model developed to classify HER2 status in BC cell lines and was refined and validated for HER2 status prediction for each pt cohort (HER2+ = 3+, 2+/ISH+; HER2- = 2+/ISH-, 1+, 0). The BC cell-line derived HER2 classifier was refined to incorporate GEA and OV cancer specific features before being applied to those samples. Performance was assessed via AUC in a leave-one-out cross-validation schema. We also evaluated HER2 status at progression in a subset of pts with benchmarked HER2 IHC to assess dynamic changes in receptor status by LBx. Results: The epigenomic HER2 classifier was applied to all samples with ctDNA detectable by ichorCNA (90 of 179; 50%). HER2 classification of BC pts by epigenomic liquid biopsy was concordant with standard tissue-based IHC for 64/72 (89%) BC samples (AUC 0.9, table). HER2 classifier predictions for all longitudinally collected samples were concordant with IHC-based HER2 status, including the one patient whose status switched from HER2+ to HER2- at progression. Accurate classification of 11/14 (79%, GEA) and 4/4 (100%, OV) pts was achieved using the indication-refined HER2 classifier. Conclusions: We demonstrate proof of concept for a HER2 classification approach using comprehensive epigenomic signals from 1 ml of plasma that could be applied across multiple cancers. With further development, our genome-wide profiling approach could alleviate clinical constraints associated with multiple tissue-based HER2 scoring assays (IHC/ISH) and enable longitudinal monitoring of HER2 status on therapy. [Table: see text]

Impact of regulatory t cells in peripheral blood on pathological complete response in patients with locally advanced gastric or gastroesophageal junction cancer undergoing neoadjuvant chemoimmunotherapy.

e16081 Background: Neoadjuvant chemotherapy has become the standard treatment for locally advanced gastric or gastroesophageal junction (G/GEJ) cancer. With the widely clinical application of immune checkpoint inhibitors, represented by anti-PD-1 antibodies, an increasing number of patients with locally advanced G/GEJ cancer are undergoing neoadjuvant chemoimmunotherapy. However, there is currently no effective predictive marker for neoadjuvant chemoimmunotherapy in locally advanced G/GEJ cancer. We explored the role of peripheral blood regulatory T (Treg) cells in patients with locally advanced G/GEJ cancer. Methods: We retrospectively analyzed lymphocyte subpopulations before and after treatment in patients with locally advanced G/GEJ cancer who received neoadjuvant chemotherapy combined with anti-PD-1 antibodies and curative surgery. Inclusion criteria were: 1) Pathologically confirmed adenocarcinoma of the G/GEJ; 2) Clinically staged as gastric cT3-4 or N+ without distant metastasis by enhanced CT and endoscopic ultrasound examination; 3) Patients requiring neoadjuvant treatment according to gastric cancer multidisciplinary team decisions; 4) Receipt of neoadjuvant treatment with chemotherapy combined with PD-1 antibodies; 5) Completion of 3-4 cycles of treatment; 6) Underwent curative resection; 7) Lymphocyte subpopulation testing performed before the first and second cycles. Results: From July 1, 2020, to May 31, 2023, 85 patients were included. All 85 patients underwent D2 radical surgery and achieved R0 resection, with 21 patients achieving pathological complete response (pCR), resulting in a pCR rate of 24.7% (95% confidence interval (CI) 15.3-34.1%). There were no statistically significant differences in baseline characteristics between the pCR and non-pCR groups. There were no statistically significant differences in lymphocyte subpopulations between the baseline pCR and non-pCR patient groups. After one cycle of treatment (before the second cycle), there were statistically significant differences in lymphocytes, T lymphocytes, and Treg cells between the two groups. Further analysis of the absolute changes in lymphocyte subpopulations before and after one cycle of treatment revealed a greater decrease in Treg cells in the pCR group. Based on the increase or decrease in Treg cells after one cycle of treatment, the 85 patients were divided into Treg cell increase and decrease groups. The pCR rate was 11.4% (4/35, 95% CI 0.3-22.5%) in the Treg cell increase group and 34% (17/50, 95% CI 20.4-47.6%) in the Treg cell decrease group, with a statistically significant difference between the two groups ( P= 0.022). Conclusions: In locally advanced G/GEJ cancer, changes in Treg cells after one cycle of neoadjuvant treatment may serve as a predictive marker for achieving pCR.

FS-1502 in patients with HER2 high expression, locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma: An open-label, multicenter, phase II study.

e15000 Background: FS-1502 is an antibody-drug conjugate composed of an anti-HER2 antibody, linker, and Monomethylauristatin F. In this study, we conducted an open-label, multicenter, two-cohort phase II trial to evaluate the efficacy and safety of FS-1502 in HER2- positive locally advanced or metastatic gastric or gastroesophageal junction cancer. Methods: Pts with HER2-positive (IHC 3+ or 2+/FISH+) who had received ≥1 prior treatment regimens were eligible and received FS-1502 2.3 mg/kg alone every 3 weeks. The study consists of Cohort 1 for pts received ≥2 lines of previous therapy and Cohort 2 for pts only received first-line of previous therapy, respectively. The primary endpoint was the objective response rate (ORR). Secondary endpoints included progression free survival (PFS), overall survival (OS), duration of response, disease control rate, and safety. Results: At data cutoff (Dec 24,2023), 46 pts were enrolled (intent-to-treat [ITT]), 35 pts were confirmed HER2-positive (IHC 3+ or IHC 2+/ISH+, Efficacy Evaluable Set [ES]) by central laboratory. In the ES, the median age was 58.3 years, 48.6% were IHC3+ and primary tumor location in 77.1% of pts was GC. 45.7% (16/35) pts had assigned to cohort 1 and 54.3% (19/35) pts had assigned to cohort 2. In cohort 1, median study follow-up time was 10.1 months, the investigator-assessed ORR was 37.5% (95% CI, 15.2-64.6), median PFS and OS were 4.3 months (95% CI, 1.5-5.8 months) and 10.0 months (95% CI,5.1-NA months), respectively. In cohort 2, median study follow-up time was 12.5 months, the investigator-assessed ORR was 52.6% (95% CI, 28.9-75.6). PFS and OS were 4.4 months (95% CI, 3.0-7.3 months) and 14.6 months (95% CI, 8.7-NA months), respectively. Grade≥3 treatment-related TEAEs were reported in 12 (26.1%) pts, ≥5% were hypokalemia (6.5%) and fatigue(6.5%). No adverse events leading to drug discontinuation or death. Efficacy and safety data are shown in table. Conclusions: FS-1502 showed promising activity with tolerable and manageable safety profile, which warrants further development in HER2-postive, advanced gastric or gastroesophageal junction adenocarcinoma who had received ≥1 prior treatment regimens. [Table: see text]

428P Total neoadjuvant FOLFIRINOX in patients with resectable locally advanced gastric and gastroesophageal junction cancer: Updated survival results

428P Total neoadjuvant FOLFIRINOX in patients with resectable locally advanced gastric and gastroesophageal junction cancer: Updated survival results