RAD51 Expression as a Biomarker to Predict Efficacy of Preoperative Therapy and Survival for Esophageal Squamous Cell Carcinoma: A Large-cohort Observational Study (KSCC1307).

OBJECTIVE: The aim of this study is to identify biomarkers that predict efficacy of preoperative therapy and survival for esophageal squamous cell carcinoma (ESCC). BACKGROUND: It is essential to improve the accuracy of preoperative molecular diagnostics to identify specific patients who will benefit from the treatment; thus, this issue should be resolved with a large-cohort, retrospective observational study. METHODS: A total of 656 patients with ESCC who received surgery after preoperative CDDP + 5-FU therapy, docetaxel + CDDP + 5-FU therapy or chemoradiotherapy (CRT) were enrolled. Immunohistochemical analysis of TP53, CDKN1A, RAD51, MutT-homolog 1, and programmed death-ligand 1 was performed with biopsy samples obtained before preoperative therapy, and expression was measured by immunohistochemistry. RESULTS: In all therapy groups, overall survival was statistically separated by pathological effect (grade 3 > grade 2 > grade 0, 1, P < 0.0001). There was no correlation between TP53, CDKN1A, MutT-homolog 1, programmed death-ligand 1 expression, and pathological effect, whereas the proportion of positive RAD51 expression (≥50%) in cases with grade 3 was lower than that with grade 0, 1, and 2 (P = 0.022). In the CRT group, the survival of patients with RAD51-positive tumor was significantly worse than RAD51-negative expressors (P = 0.0119). Subgroup analysis of overall survival with respect to positive RAD51 expression indicated preoperative chemotherapy (CDDP + 5-FU or docetaxel + CDDP + 5-FU) was superior to CRT. CONCLUSIONS: In ESCC, positive RAD51 expression was identified as a useful biomarker to predict resistance to preoperative therapy and poor prognosis in patients who received preoperative CRT. Administration of preoperative chemotherapy may be warranted for patients with positive RAD51 expression.

Identification of SLC38A7 as a Prognostic Marker and Potential Therapeutic Target of Lung Squamous Cell Carcinoma.

BACKGROUND: No effective molecular targeted therapy has been established for SCC. We conducted a comprehensive study of SCC patients using RNA-sequencing and TCGA dataset to clarify the driver oncogene of SCC. METHOD: Forty-six samples of 23 patients were totally analyzed with RNA-sequencing. We then searched for candidate-oncogenes of SCC using the TCGA database. To identify candidate oncogenes, we used the following 2 criteria: (1) the genes of interest were overexpressed in tumor tissues of SCC patients in comparison to normal tissues; and (2) using an integrated mRNA expression and DNA copy number profiling analysis using the TCGA dataset, the DNA copy number of the genes was positively correlated with the mRNA expression. RESULT: We identified 188 candidate-oncogenes. Among those, the high expression of SLC38A7 was a strong prognostic marker that was significantly associated with a poor prognosis in terms of both overall survival (OS) and recurrence-free survival in the TCGA dataset (P < 0.05). Additionally, 202 resected SCC specimens were also subjected to an immunohistochemical analysis. Patients with the high expression of SLC38A7 (alternative name is sodium-coupled amino acid transporters 7) protein showed significantly shorter OS in comparison to those with the low expression of SLC38A7 protein [median OS 3.9 years (95% confidence interval, 2.4-6.4 years) vs 2.2 years (95% confidence interval, 1.9-4.1 years); log rank test: P = 0.0021]. CONCLUSION: SLC38A7, which is the primary lysosomal glutamine transporter required for the extracellular protein-dependent growth of cancer cells, was identified as a candidate therapeutic target of SCC.

Radiomics Texture Analysis for the Identification of Colorectal Liver Metastases Sensitive to First-Line Oxaliplatin-Based Chemotherapy.

OBJECTIVE: The aim of this study was to develop a radiomics-based prediction model for the response of colorectal liver metastases to oxaliplatin-based chemotherapy. METHODS: Forty-two consecutive patients treated with oxaliplatin-based first-line chemotherapy for colorectal liver metastasis at our institution from August 2013 to October 2019 were enrolled in this retrospective study. Overall, 126 liver metastases were chronologically divided into the training (n = 94) and validation (n = 32) cohorts. Regions of interest were manually segmented, and the best response to chemotherapy was decided based on Response Evaluation Criteria in Solid Tumors (RECIST). Patients who achieved clinical complete and partial response according to RECIST were defined as good responders. Radiomics features were extracted from the pretreatment enhanced computed tomography scans, and a radiomics score was calculated using the least absolute shrinkage and selection operator regression model in a trial cohort. RESULTS: The radiomics score significantly discriminated good responders in both the trial (area under the curve [AUC] 0.8512, 95% confidence interval [CI] 0.7719-0.9305; p < 0.0001) and validation (AUC 0.7792, 95% CI 0.6176-0.9407; p < 0.0001) cohorts. Multivariate analysis revealed that high radiomics scores greater than - 0.06 (odds ratio [OR] 23.803, 95% CI 8.432-80.432; p < 0.0001), clinical non-T4 (OR 6.054, 95% CI 2.164-18.394; p = 0.0005), and metachronous disease (OR 11.787, 95% CI 2.333-70.833; p = 0.0025) were independently associated with good response. CONCLUSIONS: Radiomics signatures may be a potential biomarker for the early prediction of chemosensitivity in colorectal liver metastases. This approach may support the treatment strategy for colorectal liver metastasis.

Expression of CD44 variant 9 induces chemoresistance of gastric cancer by controlling intracellular reactive oxygen spices accumulation.

BACKGROUND: CD44 variant 9 (CD44v9) has been reported to suppress reactive oxygen spices (ROS) in association with antioxidant factors such as glutathione (GSH) and glutathione peroxidase 2 (GPx2), resulting in promoted tumor growth. METHODS: CD44v9 and GPx2 expression were investigated by immunohistochemistry in resected specimens from 193 gastric cancer (GC) patients without preoperative chemotherapy and in pretreatment biopsy specimens from 29 GC patients with preoperative chemotherapy. We analyzed the relationship between CD44v9 expression and clinicopathological factors, prognosis, and pathological response to chemotherapy. In GC cell lines, we examined the relationship between CD44v9 expression and chemotherapeutic sensitivity. RESULTS: In patients without preoperative chemotherapy, CD44v9 expression was significantly associated with depth of invasion, lymphatic permeation, vascular invasion, distant metastasis and GPx2 expression. In multivariate analysis, CD44v9 expression was an independent poor prognosis factor for overall survival and recurrence-free survival. In patients with preoperative chemotherapy, CD44v9 expression was significantly associated with worse pathological response and GPx2 expression. In GC cell lines, downregulation of CD44v9 expression enhanced chemotherapeutic sensitivity to 5-fluorouracil with changing GSH and ROS levels. CONCLUSIONS: CD44v9-positive expression was associated with chemotherapeutic resistance by controlling intracellular accumulated ROS, suggesting that CD44v9 may be a predictive biomarker for chemotherapy in GC.

Indications for laparoscopic surgery for older rectal cancer patients with comorbidities.

PURPOSE: Given the lack of safety studies concerning laparoscopic surgery for rectal cancer in patients ≥ 80 years old with comorbidities, we sought to investigate this in the current study. METHODS: Between 2012 and 2019, 24 patients ≥ 80 years old underwent laparoscopic surgery for rectal cancer without preoperative treatment. These patients were divided into those with [comorbidity(+) group, n = 13] and without [comorbidity(-) group, n = 11] comorbidities. The preoperative nutritional status and ASA classification, postoperative complications, time to oral diet, and length of hospital stay were evaluated in each group. RESULTS: In the comorbidity(+)/comorbidity(-) groups, the average age was 85.9/84.1 years old, respectively. The major comorbidities were heart disease including atrial fibrillation and valvular disorder. The average PNI and CONUT scores in the comorbidity(+)/comorbidity(-) groups were 44.7/44.2 an 3.1/2.2, respectively. Planned surgical procedures were completed in all patients. Postoperative complications occurred in 2/3 cases in the comorbidity(+)/comorbidity(-) groups, respectively, and the average time to oral diet was 3.8/3.7 days, while the average length of hospitalization after surgery was 15.2/16.5 days, respectively. In the comorbidity(+) group, there was no exacerbation of comorbidities in any cases. CONCLUSION: The safety of laparoscopic surgery is acceptable among older rectal cancer patients with comorbidities.

[The Efficacy of topo â -pS10 Expression in Gastric Cancer as a Predictive Biomarker for Irinotecan Use].

BACKGROUND: Though irinotecan is commonly used for treating advanced gastric cancer, there is no predictive biomarker to date. We have studied the resistant mechanism for irinotecan and found that phosphorylation of serine 10 residue of topoisomerase Ⅰ(topo Ⅰ)is an important step for irinotecan resistance. We have developed an immunohistochemical staining-based biomarker; topo Ⅰ-pS10, for predicting irinotecan efficacy. PURPOSE: The purpose of this study is to test the accuracy of topo Ⅰ-pS10 immunohistochemical staining in gastric cancer clinical samples. METHODS: In this study we performed 2 sets of tests. In the training set, we stained 79 gastric cancer clinical samples which efficacy of irinotecan was measured by succinate dehydrogenase inhibition(SDI)test. In the validation set, we used 27 gastric cancer clinical samples which irinotecan was used and the efficacy was known. RESULTS: Training set: From the ROC curve the cut-off point was set at 35% positive nuclei. Sixty three cases were positive with topo Ⅰ-pS10 in the nuclei. With the result of irinotecan SDI, the sensitivity was 76.6% and the positive predictive value was 92.5%. This result showed that topo Ⅰ-pS10 positive case does not respond to irinotecan. Validation set: In this set, the sensitivity was 82.4% and the positive predictive value was 82.4%. CONCLUSION: topo Ⅰ-pS10 staining can be used as a predictive biomarker for irinotecan for gastric cancer patients.

Prognostic Impact of Programmed Death-Ligand 2 Expression in Primary Lung Adenocarcinoma Patients.

BACKGROUND: Programmed death-ligand 1 (PD-L1) expression on lung cancer cells is a prognostic marker and a predictive biomarker for response to immunotherapy. However, previous clinical trials have suggested that other programmed cell death 1 ligands, including programmed death-ligand 2 (PD-L2), might have clinical impacts. This study aimed to analyze the prognostic significance of PD-L2 expression in lung adenocarcinoma patients. METHODS: The study included 433 patients who underwent surgical resection for lung adenocarcinoma between 2003 and 2012 at Kyushu University Hospital. Both PD-L1 and PD-L2 expression were evaluated by immunohistochemistry. The cutoff value for PD-L2 positivity was set at 1% according to a time-dependent receiver operating characteristic curve for 5-year survival. RESULTS: Of the 433 patients, 306 (70.7%) were positive for PD-L2. No significant association between PD-L1 and PD-L2 expression was observed (P = 0.094). The multivariate analysis showed that the independent predictors of PD-L2 positivity were never-smoker status (P = 0.002), poor differentiation grade (P = 0.008), and advanced stage (P = 0.048). The PD-L2-positive patients had significantly shorter disease-free survival (DFS) (P = 0.018) and overall survival (OS) (P = 0.016). Both PD-L1 and PD-L2 positivity were independent predictors of OS (P < 0.001 and P = 0.027, respectively). In the subgroup analysis of the PD-L1-negative patients, PD-L2 positivity was significantly associated with shorter DFS (P = 0.018). CONCLUSIONS: The study demonstrated that the clinical characteristics of patients with PD-L1 expression may differ from those of patients with PD-L2 expression, and that both might contribute to poor prognoses. The potential role of PD-L2 expression as a predictive biomarker for response to immunotherapy should be investigated in future studies.

C-reactive protein/albumin ratio is a poor prognostic factor of esophagogastric junction and upper gastric cancer.

BACKGROUND AND AIM: The C-reactive protein (CRP)/albumin (Alb) ratio has been reported as a novel prognostic marker in several cancers. The objective of this study was to investigate the prognostic value of the CRP/Alb ratio in patients who underwent surgery for adenocarcinoma of the esophagogastric junction (AEG) and upper gastric cancer (UGC). METHODS: Data for 144 patients who underwent surgery for AEG and UGC were reviewed. The CRP/Alb ratio, neutrophil-lymphocyte ratio, platelet-lymphocyte ratio, Glasgow Prognostic Score, and controlling nutritional status score were calculated, and the relationship between these biomarkers and postoperative prognosis was analyzed. RESULTS: The optimal cutoff value of the CRP/Alb ratio was determined to be 0.1. According to the cutoff value of CRP/Alb ratio, patients were divided into two groups (CRP/Alb < 0.1, n = 124; CRP/Alb ≥ 0.1, n = 20). The 5-year recurrence-free survival and overall survival (OS) rates were significantly lower in the patients with the CRP/Alb ratio ≥ 0.1 than in those with the CRP/Alb ratio < 0.1 (recurrence-free survival: 44.9% vs 77.9%, P = 0.0011; OS: 43.4% vs 82.0%, P < 0.0001). In the multivariate analyses, the N-stage, and CRP/Alb ratio ≥ 0.1 were identified as independent predictive factors for OS in patients with AEG and UGC (P = 0.0061 and P = 0.0439, respectively). CONCLUSIONS: The CRP/Alb ratio was strongly associated with poor prognosis in patients who underwent surgery for AEG and UGC.

Comparison of computed tomography imaging analyses for evaluation after chemotherapy in patients with colorectal cancer: a retrospective pooled analysis of six phase II clinical trials.

BACKGROUND: There are several methods for analyzing computed tomography (CT) images to evaluate chemotherapy efficacy in clinical studies. However, the optimal analysis method for each drug is still under debate. We conducted a pooled analysis using data from six phase II studies to evaluate four analysis methods in colorectal cancers (CRCs): morphological responses (MRs), early tumor shrinkage (ETS), depth of response (DpR), and response evaluation criteria in solid tumors (RECIST) ver.1.1. METHODS: We included 249 patients in this analysis. Pretreatments and findings of subsequent CT imaging were analyzed based on the MR, ETS, DpR, and RECIST ver.1.1. Differences in overall survival (OS) between the responders and non-responders according to each method were evaluated using survival analysis. RESULTS: The responders had significantly better hazard ratios (HRs) for OS, in terms of DpR (≥ median), ETS, objective response rate (ORR) [complete response (CR) + partial response (PR)], and disease control rate [CR + PR + stable disease (SD)]. Patients with right-sided colon cancers showed better HRs for DpR, but not for ETS and ORR. Contrastingly, patients with left-sided CRCs had better HRs for ETS, DpR, and ORR. MR was not associated with outcomes in this study, even in cases where bevacizumab was used. In patients with liver metastasis, ETS, DpR, and ORR showed better HRs, but not in those with lung metastasis. CONCLUSION: Early tumor shrinkage and DpR might be predictive markers only in left-sided CRCs with liver metastasis. Each imaging analysis has a different value based on the primary and metastatic sites.

Neoadjuvant Chemoradiotherapy for Patients with cT3/Nearly T4 Esophageal Cancer: Is Sarcopenia Correlated with Postoperative Complications and Prognosis?

BACKGROUND: Since the clinical impact of sarcopenia on multimodal therapy for patients with esophageal cancer is not well understood, this study was conducted to determine the influence of sarcopenia on the efficacy of neoadjuvant chemoradiotherapy (NACRT) for locally advanced esophageal cancer. METHODS: The skeletal muscle index was quantified at the level of the third lumbar vertebra on computed tomography images, and sarcopenia was defined as a skeletal muscle index that was less than the average for each gender. We compared treatment outcomes in patients with cT3 and nearly T4 thoracic esophageal squamous cell carcinoma between the sarcopenia group (n = 85) and the non-sarcopenia group (n = 72). RESULTS: The 5-year survival rates were 33.4% in the non-sarcopenia group and 31.5% in the sarcopenia group; these differences were not significant. The prognosis of the patients with sarcopenia was worse than that of the patients without sarcopenia in the surgery-alone group, but there was no difference between patients with and without sarcopenia in the NACRT group. CONCLUSIONS: NACRT could be a useful option for patients with locally advanced esophageal squamous cell carcinoma, even for those with sarcopenia, without increasing the incidence of morbidity and mortality.

Sarcopenia is an independent predictor of complications after colorectal cancer surgery.

PURPOSE: The significance of sarcopenia after colorectal cancer (CRC) resection has only been discussed with relatively small samples or short follow-up periods. This study aimed to clarify the clinical significance of sarcopenia in a large-sample study. METHODS: We retrospectively analyzed the relationship between sarcopenia and clinical factors, surgical outcomes, and the survival in 494 patients who underwent CRC surgery between 2004 and 2013. Sarcopenia was defined based on the sex-specific skeletal muscle mass index measured by preoperative computed tomography. RESULTS: Sarcopenia was associated with sex (higher rate of male, P < 0.0001), and low body mass index (P < 0.0001), but not age or tumor stage. Sarcopenia was associated with higher incidence of all postoperative complications (P = 0.02), especially for patients with Clavien-Dindo classification grade ≥2 (CDC; P = 0.0007). Postoperative hospital stays were significantly longer for sarcopenic patients than for non-sarcopenic patients (P = 0.02). In a multivariate analysis, sarcopenia was an independent predictor for postoperative complications (P = 0.01, odds ratio 1.82, 95% confidence interval 1.13-3.00). Among postoperative complications (CDC grade ≥2), sarcopenia was correlated with non-surgical-site infections (P = 0.03). Sarcopenia was not correlated with the overall or recurrence-free survival. CONCLUSIONS: Sarcopenia was an independent predictive factor for postoperative complications after CRC surgery.

[Resected Pulmonary Cryptococcosis Suspected as Lung Cancer;Report of a Case].

We report a case of pulmonary cryptococcosis suspected of lung cancer. A 65-year-old woman had an abnormal shadow on chest X-ray. A solitary nodule, 12 mm in size, with pleural indentation and spicula in S3 of the left lung was found on chest computed tomography. A serum cryptococcal antigen was negative. An abnormal accumulation of fluoro-2-deoxy-D-glucose(FDG)in the nodule was found with the standardized uptake value (SUV) max 5.04, suggesting lung cancer. The nodule was diagnosed as pulmonary cryptococcosis by surgical resection.

Influence of Robotic Rectal Resection Versus Laparoscopic Rectal Resection on Postoperative Ileus: A Single-center Experience.

AIM: This study was performed to clarify the relationship between robotic rectal resection and postoperative ileus (POI) by comparing robotic surgery with laparoscopic surgery. MATERIALS AND METHODS: We retrospectively reviewed 238 patients who underwent robotic (n=41) or laparoscopic (n=197) rectal resection for rectal cancer in our institution from January 2013 to June 2020. First, we compared the background factors and short-term surgical outcomes between robotic and laparoscopic surgery. Next, we investigated the postoperative complications of robotic and laparoscopic rectal resection. Finally, we identified the risk factors for POI following rectal cancer resection. RESULTS: The percentages of patients with an Rb tumor location, treatment by abdominoperitoneal resection/intersphincteric resection/low anterior resection, a temporary diverting ileostomy, and a long operation time were significantly higher in robotic than laparoscopic surgery ( P <0.0001, P =0.0002, P =0.0078, and P =0.0001, respectively). There was no significant difference in any individual postoperative complication between robotic and laparoscopic surgery. Risk factors for POI were male sex ( P =0.0078), neoadjuvant chemoradiotherapy ( P =0.0007), an Rb tumor location ( P =0.0005), treatment by abdominoperitoneal resection/intersphincteric resection/low anterior resection ( P =0.0044), a temporary diverting ileostomy ( P <0.0001), and operation time of ≥240 minutes ( P =0.0024). Notably, robotic surgery was not a risk factor for POI following rectal resection relative to laparoscopic surgery. CONCLUSION: Although patients who underwent robotic surgery had more risk factors for POI, the risk of POI was similar between robotic and laparoscopic rectal resection.

Impact of a Long Linear Staplers on the Incidence of Stricture after Triangulating Esophagogastric Anastomosis.

BACKGROUND: Various techniques have been reported for esophagogastric anastomosis to prevent anastomotic leakage. Recently, not only postoperative anastomotic leakage but also anastomotic stricture is considered important because stricture contributes to the patient's postoperative quality of life. However, the best procedure for anastomosis has not been established. MATERIALS AND METHODS: The authors divided 101 patients with thoracic or abdominal esophageal cancer who underwent cervical triangulating esophagogastric anastomosis using a linear stapler between May 2017 and May 2020 into 2 groups: surgery with a short (45 mm) linear stapler (SS group, n=59) or a long (60 mm) stapler (LS group, n=42). The frequencies of anastomotic leakage and stricture were compared between the 2 groups. RESULTS: The incidence of anastomotic leakage and stricture without leakage were significantly lower in the LS versus SS group (respectively: leakage: 15% vs. 0%, P=0.01; stricture: 36% vs. 7%, P=0.01). A short linear stapler and anastomotic leakage were independent risk factors for anastomotic stricture in the multivariate analysis (short stapler: odds ratio, 3.27; 95% confidence interval, 1.08-9.9; P=0.03; anastomotic leakage: odds ratio, 2.78; 95% confidence interval, 1.02-8.5; P=0.04). CONCLUSION: A long linear stapler is preferable for cervical triangulating esophagogastric anastomosis.

Cytolytic activity score as a biomarker for antitumor immunity and clinical outcome in patients with gastric cancer.

BACKGROUND: A simple measure of immune cytolytic activity (CYT) base on mRNA expression levels of two genes, GZMA and PRF1, was recently reported. Here, we aimed to evaluate the CYT score's potential as a measure of antitumor immunity and predictor of clinical outcome in gastric cancer (GC) patients. MATERIALS AND METHODS: We evaluated the correlations between tumor-infiltrating immune cells and the CYT score in 238 GC samples from The Cancer Genome Atlas (TCGA). Next, we investigated CYT score associations with molecular subtypes, somatic mutation load, and immune checkpoint molecules in GC samples from TCGA and Asian Cancer Research Group (ACRG). Moreover, we evaluated the clinical significance of the CYT score calculated by reverse transcription (RT)-quantitative PCR (qPCR) data in 123 GC samples and the association of the CYT score with the response to anti-PD-1 therapy in 7 GC samples from Kyushu University Hospital. RESULTS: The CYT score positively correlated with the proportions of tumor-infiltrating CD8+ T cells and macrophages and negatively correlated with the proportion of regulatory T cells in GC tissues. A high CYT score was associated with common immune checkpoint molecules, a high mutation, the Epstein-Barr virus subtype, and the microsatellite instability subtype in GC. Moreover, a low CYT score was a poor prognosis factor in patients with GC. Finally, the CYT score was higher in a responder to anti-PD-1 therapy compared to nonresponders. CONCLUSION: The CYT score reflects antitumor immunity and predicts clinical outcome in GC patients.

Quadruple gastrointestinal cancer with discordance of mismatch repair protein deficiency and microsatellite instability suggesting Lynch syndrome.

A 65-year-old woman with prior personal and family histories of cancer was admitted to our hospital for quadruple cancer. Preoperative endoscopy revealed a type 0-II gastric cancer (GC; gastric body), advanced type-II colon cancer (ascending colon), and early-stage recto-sigmoid colon cancers. We diagnosed her with Lynch syndrome (LS) per Amsterdam criteria, and performed distal gastrectomy, ileocecal resection and high anterior resection. Her pathological diagnoses were GC: well-to-poorly differentiated adenocarcinoma (AD, por2 > tub2) with signet-ring cells, ypT1b SM2; ascending colon cancer: AD with focal mucin products (tub2 > muc), SS; sigmoid colon cancer: AD (tub1), M; recto-sigmoid cancer: AD (tub1 > tub2), SM. Immunohistochemical tests revealed that all cancers lacked the MLH1/PMS2 protein. However, the three colon cancers were found to have high microsatellite instability (MSI); the GC was microsatellite stable (MSS). No recurrence or other cancers were observed for 30 months after surgery without adjuvant chemotherapy. As patients with LS may also develop MSS cancers, we should check for MSI in all LS cancers for proper treatment.

Circulating Tumor DNA Analysis Detects FGFR2 Amplification and Concurrent Genomic Alterations Associated with FGFR Inhibitor Efficacy in Advanced Gastric Cancer.

PURPOSE: FGFR2 amplification is associated with poor prognosis in advanced gastric cancer and its subclonal heterogeneity has been revealed. Here, we examined whether circulating tumor DNA (ctDNA) was useful for detecting FGFR2 amplification and co-occurring resistance mechanisms in advanced gastric cancer. EXPERIMENTAL DESIGN: We assessed genomic characteristics of FGFR2-amplified advanced gastric cancer in a nationwide ctDNA screening study. We also analyzed FGFR2 amplification status in paired tissue and plasma samples with advanced gastric cancer. In addition, we examined patients with FGFR2-amplified advanced gastric cancer identified by ctDNA sequencing who received FGFR inhibitors. RESULTS: FGFR2 amplification was more frequently detected by ctDNA sequencing in 28 (7.7%) of 365 patients with advanced gastric cancer than by tissue analysis alone (2.6%-4.4%). FGFR2 amplification profiling of paired tissue and plasma revealed that FGFR2 amplification was detectable only by ctDNA sequencing in 6 of 44 patients, which was associated with a worse prognosis. Two patients in whom FGFR2 amplification was detected by ctDNA sequencing after tumor progression following previous standard chemotherapies but not by pretreatment tissue analysis had tumor responses to FGFR inhibitors. A third patient with FGFR2 and MET co-amplification in ctDNA showed a limitation of benefit from FGFR inhibition, accompanied by a marked increase in the MET copy number. CONCLUSIONS: ctDNA sequencing identifies FGFR2 amplification missed by tissue testing in patients with advanced gastric cancer, and these patients may respond to FGFR inhibition. The utility of ctDNA sequencing warrants further evaluation to develop effective therapeutic strategies for patients with FGFR2-amplified advanced gastric cancer.