Incidence and factors associated with stent dysfunction and pancreatitis after gastroduodenal stenting for malignant gastric outlet obstruction.

Background and study aims Endoscopic gastroduodenal stent (GDS) deployment is currently a standard treatment for malignant gastric outlet obstruction (mGOO) in patients with limited life expectancy; however, stent dysfunction (SD) and complicated pancreatitis often occur after GDS deployment. We investigated incidence and contributing factors of SD and complicated pancreatitis. Patients and methods We retrospectively reviewed 203 patients who underwent initial GDS deployment for palliation of mGOO symptoms between October 2017 and July 2022, including 109 who underwent GDS deployment across the duodenal papilla (sub-cohort). Results SDs, including tumor ingrowth (n = 26), kinking (n = 14), and migration (n = 13), occurred in 68 patients (33.5%). Cumulative SD incidence was 41.1% (95% confidence interval, 32.6-49.4%). SD incidence increased to 0.4%, 0.16%, and 0.06% per day at < 8, 8-16, and>16 weeks, respectively. On multivariate analysis, Niti-S pyloric/duodenal stent deployment (sub-distribution hazard ratio [sHR] 0.26, P = 0.01) and survival length ≥ 90 days (sHR 2.5, P = 0.01) were respectively identified as favorable and risk factors significantly associated with SD. Pancreatitis developed in 14 patients (12.8%) in the sub-cohort, which had significantly higher parenchymal diameter ( P < 0.01) and lower main pancreatic duct (MPD) caliber ( P < 0.01) than the non-pancreatitis cohort. On multivariate analysis, MPD caliber < 3 mm independently predicted pancreatitis (odds ratio 6.8, P = 0.03). Conclusions Deployment of the Niti-S pyloric/duodenal stent, with conformability even for angulated strictures, significantly reduced the incidence of SD. Stent selection, life expectancy, and MPD caliber should be taken into consideration during decision-making for GDS deployment for mGOO.

Pivotal role of myeloid-derived suppressor cells in infection-related tumor growth.

BACKGROUND: In this study, we investigated infection-related tumor growth, focusing on myeloid-derived suppressor cells (MDSCs) in clinical and experimental settings. PATIENTS AND METHODS: In the clinical study, a total 109 patients who underwent gastrectomy or esophagectomy were included. Blood samples were collected from a preoperative time point through 3 months after surgery, and MDSCs were analyzed using flow cytometry. In animal experiments, peritonitis model mice were created by CLP method. We investigated the number of splenic MDSCs in these mice using flow cytometry. Malignant melanoma cells (B16F10) were inoculated on the back of the mice, and tumor growth was monitored. We compared the level of MDSC infiltration around the tumor and the migration ability between CLP and sham-operated mice-derived MDSCs. Finally, we focused on PD-L1+ MDSCs to examine the effectiveness of anti-PD-L1 antibodies on tumor growth in CLP mice. RESULTS: In patients with postoperative infectious complication, MDSC number was found to remain elevated 3 months after surgery, when the inflammatory responses were normalized. CLP mice showed increased numbers of MDSCs, and following inoculation with B16F10 cells, this higher number of MDSCs was associated with significant tumor growth. CLP-mice-derived MDSCs had higher levels of accumulation around the tumor and had more enhanced migration ability. Finally, CLP mice had increased numbers of PD-L1+ MDSCs and showed more effective inhibition of tumor growth by anti-PD-L1 antibodies compared to sham-operated mice. CONCLUSION: Long-lasting enhanced MDSCs associated with infection may contribute to infection-related tumor progression.

Treatment Decision for Locally Resected T1 Colorectal Carcinoma-Verification of the Japanese Guideline Criteria for Additional Surgery Based on Long-Term Clinical Outcomes.

INTRODUCTION: To verify the value of the pathological criteria for additional treatment in locally resected pT1 colorectal carcinoma (CRC) which have been used in the Japanese Society for Cancer of the Colon and Rectum (JSCCR) guidelines since 2009. METHODS: We enrolled 4,719 patients with pT1 CRC treated at 27 institutions between July 2009 and December 2016 (1,259 patients with local resection alone [group A], 1,508 patients with additional surgery after local resection [group B], and 1,952 patients with surgery alone [group C]). All 5 factors of the JSCCR guidelines (submucosal resection margin, tumor histologic grade, submucosal invasion depth, lymphovascular invasion, and tumor budding) for lymph node metastasis (LNM) had been diagnosed prospectively. RESULTS: Any of the risk factors were present in 3,801 patients. The LNM incidence was 10.3% (95% confidence interval 9.3-11.4) in group B/C patients with risk factors, whereas it was 1.8% (95% confidence interval 0.4-5.2) in those without risk factors ( P < 0.01). In group A, the incidence of recurrence was 3.4% in patients with risk factors, but it was only 0.1% in patients without risk factors ( P < 0.01). The disease-free survival rate of group A patients classified as risk positive was significantly worse than those of groups B and C patients. However, the 5-year disease-free survival rate in group A patients with no risk was 99.2%. DISCUSSION: Our large-scale real-world multicenter study demonstrated the validity of the JSCCR criteria for pT1 CRC after local resection, especially regarding favorable outcomes in patients with low risk of LNM.

Impact of the COVID-19 pandemic on the number and short-term outcomes in hepatectomy for hepatocellular carcinoma: Results from the Japanese National Clinical Database, 2018-2021.

AIM: The coronavirus disease 2019 (COVID-19) pandemic has significantly impacted the allocation of medical resources, including cancer screening, diagnosis, and treatment. We aimed to investigate the effects of the pandemic on morbidity and mortality following hepatectomy for hepatocellular carcinoma (HCC). METHODS: We identified patients who underwent hepatectomy for HCC between 2018 and 2021 from the Japanese National Clinical Database (NCD). The number of surgical cases, the use of intensive care units, and the incidence of morbidity were assessed. The standardized morbidity / mortality ratio (SMR) was used to evaluate the rates of morbidity (bile leakage and pneumonia) and mortality in each month, which compares the observed incidence to the expected incidence calculated by the NCD's risk calculator. RESULTS: The study included a total of 10 647 cases. The number of patients undergoing hepatectomy for HCC gradually decreased. The proportion of patients aged 80 years or older increased and that of cases with T1 stage decreased. The proportion of patients who were admitted to the intensive care unit did not change between the pre- and postpandemic period. The mean actual incidence rates of bile leakage, pneumonia, 30-day mortality, and surgical mortality were 9.2%, 2.3%, 1.4%, and 2.1%, respectively. The SMR for the mortalities and morbidities in each month did not increase mostly throughout the COVID-19 pandemic. CONCLUSIONS: The present study showed the decreasing number of resected cases for HCC, while the surgical safety for hepatectomy was enough to be maintained by managing medical resources in Japan.

Idiopathic myointimal hyperplasia of mesenteric veins: radiological evaluation using CT angiography.

A 44-year-old man presented with a chief complaint of constipation. Initial contrast-enhanced CT showed extensive bowel wall thickening, mainly in the left colon, with a thin cord-like inferior mesenteric vein (IMV), in contrast to ectatic mesenteric venous branches, suggesting bowel ischaemia owing to venous stasis. One month later, at the time of symptom exacerbation, CT angiography showed a cord-like IMV and ectatic mesenteric venous branches with early enhancement, suggesting the presence of an arteriovenous fistula (AVF). Owing to the progression of bowel ischaemia and necrosis with peritonitis, emergency surgery was performed. Surgical specimens showed focal myointimal hyperplasia of the proximal mesenteric veins in both ischaemic and non-ischaemic lesions of the resected colon, thus leading to the diagnosis of idiopathic myointimal hyperplasia of mesenteric veins (IMHMV) when combined with the clinical and imaging findings. IMHMV is a bowel ischaemic disease caused by non-thrombotic venous obstruction that requires bowel resection and has been suggested to be associated with AVF. Cord-like IMV and AVF in the mesentery are important CT findings that characterize IMHMV. CT angiography is useful in diagnosing IMHMV.

Histological differentiation between sporadic and colitis-associated intestinal cancer in a nationwide study: A propensity-score-matched analysis.

BACKGROUND AND AIM: Colitis-associated intestinal cancer (CAC) can develop in patients with inflammatory bowel disease; however, the malignant grade of CAC may differ from that of sporadic colorectal cancer (CRC). Therefore, we compared histological findings distinct from cancer stage between CAC and sporadic CRC to evaluate the features of CAC. METHODS: We reviewed the clinical and histological data collected from a nationwide database in Japan between 1983 and 2020. Patient characteristics were compared to distinguish ulcerative colitis (UC), Crohn's disease (CD), and sporadic CRC. Comparisons were performed by using all collected data and propensity score-matched data. RESULTS: A total of 1077 patients with UC-CAC, 297 with CD-CAC, and 136 927 with sporadic CRC were included. Although the prevalence of well or moderately differentiated adenocarcinoma (Tub1 and Tub2) decreased according to tumor progression for all diseases (P < 0.01), the prevalence of other histological findings, including signet ring cell carcinoma, mucinous carcinoma, poorly differentiated adenocarcinoma, or squamous cell carcinoma, was significantly higher in CAC than in sporadic CRC. Based on propensity score-matched data for 982 patients with UC and 268 with CD, the prevalence of histological findings other than Tub1 and Tub2 was also significantly higher in those with CAC. At pT4, mucinous carcinoma occurred at a significantly higher rate in patients with CD (45/86 [52.3%]) than in those with sporadic CRC (13/88 [14.8%]) (P < 0.01). CONCLUSION: CAC, including early-stage CAC, has a higher malignant grade than sporadic CRC, and this difference increases in significance with tumor progression.

Impact of COVID-19 pandemic on short-term outcomes after low anterior resection in patients with rectal cancer: Analysis of data from the Japanese National Clinical Database.

Aim: The Coronavirus Disease 2019 (COVID-19) pandemic affected the allocation of various medical resources to several areas, including intensive care units (ICUs). However, currently, its impact on the short-term postoperative outcomes of gastrointestinal cancer surgeries remains unclear. We aimed to evaluate the impact of the pandemic on the incidence of complications occurring after low anterior resection in patients with rectal cancer in Japan. Methods: Data from the Japanese National Clinical Database between 2018 and 2021 were retrospectively examined. The primary outcome of the study was the postoperative morbidity and mortality rates before and after COVID-19 pandemic. Moreover, the postoperative ICU admission rate was assessed. Morbidity and mortality rates were also assessed using a standardized morbidity/mortality ratio (SMR, the ratio of the actual number of incidences to the expected number of incidences calculated by the risk calculator). Results: This study included 74 181 patients, including 43 663 (58.9%) from COVID-19 epidemic areas. The mean actual incidences of anastomotic leakage (AL) and pneumonia during the study period were 9.2% and 0.9%, respectively. The SMRs of these complications did not increase during the pandemic but those of AL declined gradually. The mean 30-day mortality and operative mortality rates were 0.3% and 0.5%, respectively. Moreover, SMRs did not change significantly in the pandemic or regional epidemic status. The ICU admission rate temporarily decreased, especially in the epidemic areas. Conclusion: Although the pandemic temporarily decreased the ICU admission rate, its impact on short-term outcomes following low anterior resection in patients with rectal cancer was insignificant in Japan.

No difference in the incidence of postoperative pulmonary complications between abdominal laparoscopy and laparotomy for minimally invasive thoracoscopic esophagectomy: a retrospective cohort study using a nationwide Japanese database.

INTRODUCTION: There remains a lack of evidence regarding the optimal abdominal approach, including laparoscopy, hand-assisted, and open laparotomy for minimally invasive thoracoscopic esophagectomy. We aimed to compare the incidence of postoperative complications, particularly pulmonary complications, between laparoscopy and open laparotomy for minimally invasive thoracoscopic esophagectomy using nationwide Japanese databases. METHODS: Data from patients in the National Clinical Database (NCD) who underwent thoracoscopic esophagectomy for esophageal cancer were analyzed. The incidence of pulmonary complications was compared between abdominal laparoscopy and laparotomy after matching the propensity scores (PS) from preoperative factors to account for confounding bias. Laparoscopic-assisted surgery (LAS) was also compared to hand-assisted laparoscopic surgery (HALS). RESULTS: Of the 24,790 patients who underwent esophagectomy between 2018 and 2021, data from 12,633 underwent thoracoscopic procedure. The proportion of patients who experienced pulmonary complications did not significantly differ between the laparoscopy group and the laparotomy group after matching (664/3195 patients, 20.8% versus 702/3195 patients, 22.0%; P = 0.25). No difference in the incidence of pulmonary complications was observed among patients treated using the laparoscopic approach (508/2439 patients, 20.8% in the LAS group versus 498/2439 patients, 20.4% in the HALS group; P = 0.72). CONCLUSIONS: We observed no significant difference in the incidence of postoperative pulmonary complications between laparoscopy and laparotomy for thoracoscopic esophagectomy. Short-term outcomes were similar between the laparoscopic-assisted approach and the hand-assisted approach. This study provides valuable insights into the optimal abdominal approach for thoracoscopic esophagectomy using data from a nationwide database that reflect real-world clinical practice.

How Does Omitting Additional Surgery After Local Excision Affect the Prognostic Outcome of Patients With High-risk T1 Colorectal Cancer?

OBJECTIVE: To investigate how omitting additional surgery after local excision (LE) affects patient outcomes in high-risk T1 colorectal cancer (CRC). BACKGROUND: It is debatable whether additional surgery should be performed for all patients with high-risk T1 CRC regardless of the tolerability of invasive procedures. METHODS: Patients who had received LE for T1 CRC at the Japanese Society for Cancer of the Colon and Rectum institutions between 2009 and 2016 were analyzed. Those who had received additional surgical resection and those who did not were matched one-on-one by the propensity score-matching method. A total of 401 propensity score-matched pairs were extracted from 1975 patients at 27 Japanese Society for Cancer of the Colon and Rectum institutions and were compared. RESULTS: Regional lymph node metastasis was observed in 31 (7.7%) patients in the LE + surgery group. Comparatively, the incidence of oncologic adverse events was low in the LE-alone group, such as the 5-year cumulative risk of local recurrence (4.1%) or overall recurrence (5.5%). In addition, the difference in the 5-year cancer-specific survival between the LE + surgery and LE-alone groups was only 1.8% (99.7% and 97.9%, respectively), whereas the 5-year overall survival was significantly lower in the LE-alone group than in the LE + surgery group [88.5% vs 94.5%, respectively ( P = 0.002)]. CONCLUSIONS: Those who had decided to omit additional surgery at the dedicated center for CRC treatment presented a small number of oncologic events and a satisfactory cancer-specific survival, which may suggest an important role of risk assessment regarding nononcologic adverse events to achieve a best practice for each individual with high-risk T1 tumors.

Study protocol for a prospective, multicentre, phase II trial on endoscopic treatment using two fully covered self-expandable metallic stents for benign strictures after hepaticojejunostomy.

INTRODUCTION: The current endoscopic treatment for postoperative benign hepaticojejunostomy anastomotic stricture (HJAS) has a high technical success rate and is highly effective in the short term. However, long-term results have shown a high rate of stenosis recurrence, which indicates an insufficient response to treatment. Three prospective studies on fully covered self-expandable metallic stent (FC-SEMS) treatment for benign HJAS used the stenosis resolution rate as the primary endpoint, and no study has yet used the long-term non-stenosis rate (at 12 months) as the primary endpoint. METHODS AND ANALYSIS: We launched the 'saddle-cross study', which will be conducted as a multicentre, prospective intervention of endoscopic treatment using two modified FC-SEMSs (BONASTENT️ M-Intraductal) that have been improved for benign stenosis in patients with benign HJAS, with the long-term non-restenosis rate (at 12 months) as the primary endpoint. This study aims to evaluate the long-term non-restenosis rate (at 12 months) and safety of the saddle-cross technique for benign HJAS. We plan to enrol 50 participants. ETHICS AND DISSEMINATION: This study has been approved by the Certified Review Board of the National Cancer Center, Japan (CRB3180009). The results will be reported at various conferences and published in international peer-reviewed journals.

The impact of COVID-19 for postoperative outcomes using a nationwide Japanese database of patients undergoing distal gastrectomy for gastric cancer.

Background: The coronavirus disease 2019 (COVID-19) pandemic had resulted in either failure to provide required medical resources or delayed treatment for gastric cancer patients. This study aimed to investigate the impact of COVID-19 on the incidence of postoperative complications using a nationwide Japanese database of patients undergoing distal gastrectomy for gastric cancer. Methods: We collected the data of patients who underwent distal gastrectomy from January 2018 to December 2021 from the National Clinical Database (NCD), a web-based surgical registration system in Japan. The number of surgical cases, the use of intensive care units, and the incidence of morbidity per month were analyzed. We also calculated the standardized mortality ratio (SMR), defined as the ratio of the number of observed patients to the expected number of patients calculated using the risk calculator established in the NCD, for several morbidities, including pneumonia, sepsis, 30-day mortality, and surgical mortality. Results: A decrease of 568 gastrectomies was observed from April 2020 to May 2020. Although the absolute number of patients admitted to intensive care units had declined since 2020, the proportion of patients admitted to the ICU did not change before and after the pandemic. Mortality and critical morbidity (such as pneumonia and sepsis) rates were not worse during the pandemic compared to pre-pandemic periods per the SMR. Conclusions: Surgical management was conducted adequately through the organized efforts of the entire surgery department in our country even in a pandemic during which medical resources and staff may have been limited.

Clinical features of germline BRCA1/2 or ATM pathogenic variant positive pancreatic cancer in Japan.

BACKGROUND: There has been increasing interest into the role of germline BRCA1/2 pathogenic variants (gBRCA PV) and gATM PV and likely PV (PV and LPV; PV + LPV) in the carcinogenesis and treatment of pancreatic cancer (PC), but the clinical features have not been well described. METHODS: Patients with confirmed gBRCA PV and gATM PV + LPV PC treated at our hospital between April 2016 and December 2021, were retrospectively evaluated for clinical characteristics and outcomes. RESULTS: Twenty-two patients harbored gBRCA PV and three patients harbored gATM PV + LPV. Of the gBRCA PV patients, 81.8 % received platinum-based chemotherapy with favorable treatment outcomes with an objective response rate of 50.0 % (95 % CI: 23.0-77.0), median progression free survival (PFS) of 334 days, and median overall survival (OS) of 926 days from the initiation of first-line chemotherapy. The annual number of patients with gBRCA PV was two patients per year before January 2021 (when BRACAnalysis became available in Japan), and ten patients during the 10 months thereafter. Four patients (20 %) with gBRCA PV developed soft-tissue metastasis with progression. Two patients with gATM PV + LPV received platinum-based chemotherapy and the best response of those patients was partial response and stable disease and their OS from the initiation of first-line chemotherapy was 1192 and 989 days, and PFS was 579 and 140 days, respectively. CONCLUSION: The diagnosis of gBRCA PV-positive PC has increased revealed in recent years. These tumors appear to be sensitive to platinum-based chemotherapy, with long term survival observed in gATM PV + LPV-positive patients.

A case of emphysematous intrascrotal abscess secondary to sigmoid coloseminal fistula.

A 54-year-old male patient presented with pneumaturia. Right scrotal swelling was observed. CT showed an intrascrotal abscess with gas formation. MRI showed a fistula extending from the sigmoid colon to the seminal vesicles. Since there are many diverticula in the sigmoid colon, an abscess caused by diverticulitis may have formed a fistula. The scrotal abscess was drained; however, the pus discharge did not decrease. A colostomy was then performed, and the scrotal infection rapidly improved. Sigmoidectomy and fistula transection were performed 11 months after the colostomy. Prompt diagnosis of a sigmoid coloseminal fistula using imaging has led to optimal treatment.

A proposed new Japanese classification of synchronous peritoneal metastases from colorectal cancer: A multi-institutional, prospective, observational study conducted by the Japanese Society for Cancer of the Colon and Rectum.

Aim: To establish a new Japanese classification of synchronous peritoneal metastases from colorectal cancer. Methods: This multi-institutional, prospective, observational study enrolled patients who underwent surgery for colorectal cancer with synchronous peritoneal metastases. Overall survival rates were compared according to the various models using objective indicators. Each model was evaluated by Akaike's information criterion (AIC). The region of peritoneal metastases was evaluated by the peritoneal cancer index (PCI). Results: Between October 2012 and December 2016, 150 patients were enrolled. The AIC of the present Japanese classification was 1020.7. P1 metastasis was defined as confined to two regions. The minimum AIC was obtained with the cutoff number of 10 or less for P2 metastasis and 11 or more for P3 metastasis. As for size, the best discrimination ability between P2 and P3 metastasis was obtained with a cutoff value of 3 cm. The AIC of the proposed classification was 1014.7. The classification was as follows: P0, no peritoneal metastases; P1, metastases localized to adjacent peritoneum (within two regions of PCI); P2, metastases to distant peritoneum, number ≤10 and size ≤3 cm; P3, metastases to distant peritoneum, number ≥11 or size >3 cm; P3a, metastases to distant peritoneum, number ≥11 and size ≤3 cm, or number ≤10 and size >3 cm; P3b, metastases to distant peritoneum, number ≥11 and size >3 cm. Conclusion: This objective classification could improve the ability to discriminate prognosis in patients with synchronous peritoneal metastases from colorectal cancer.

Impact of Preoperative Tumor Size on Prognosis of Resectable and Borderline Resectable Pancreatic Ductal Adenocarcinomas.

BACKGROUND: Tumor size (TS) is a well-established prognostic factor of pancreatic ductal adenocarcinoma (PDAC). However, whether a uniform treatment strategy can be applied for all resectable PDACs (R-PDACs) and borderline resectable PDACs (BR-PDACs), regardless of TS, remains unclear. This study aimed to investigate the impact of preoperative TS on surgical outcomes of patients with R-PDACs and BR-PDACs. METHODS: Chart data from three institutions were reviewed to select patients who underwent pancreatectomy for R-PDACs and BR-PDACs between January 2006 and December 2020. The patients were divided into TSsmall and TSlarge groups according to a TS cutoff value determined for each of R- and BR-PDAC using the minimum P value approach for the risk of R1 resection. RESULTS: TS of 35 mm and 24 mm was the best cutoff value in R-PDAC and BR-PDAC, respectively. The R1 rate was higher in the TSlarge than TSsmall group, in both R- (n = 35, 37% versus n = 294, 19%; P = 0.011) and BR-PDAC (n = 89, 37% versus n = 27, 15%; P = 0.030). Overall survival was significantly better in the TSsmall than TSlarge group in R-PDAC (38.2 versus 12.1 months; P < 0.001), but comparable between the two groups in BR-DPAC (21.2 versus 22.7 months; P = 0.363). Multivariate analysis revealed TS > 35 mm as an independent predictor of worse survival in patients with R-PDAC. CONCLUSION: Larger TS was associated with a higher R1 rate and is a worse prognostic factor in patients with R-PDAC.

Clinicopathological Findings and Treatment Outcomes of Patients with Primary Hepatobiliary Neuroendocrine Neoplasms: A Retrospective Single-institution Analysis.

Objective Primary hepatobiliary neuroendocrine neoplasms (NENs) are rare tumors exhibiting several morphological and behavioral characteristics. Considering the lack of relevant data on this topic, we evaluated the clinicopathological features and treatment outcomes of patients with primary hepatobiliary NENs. Methods/Patients We examined 43 consecutive patients treated at the National Cancer Center Hospital with pathological diagnoses of primary hepatobiliary NEN between 1980 and 2016. Results Nine patients were diagnosed with neuroendocrine tumor (NET) G1, 9 with NET G2, and 25 with neuroendocrine carcinoma (NEC) based on the World Health Organization 2019 classification. Patients with NEC had primary sites across the hepatobiliary organs, although sites in patients with NET G1 and NET G2 only included the liver and ampulla of Vater. Patients with primary extrahepatic bile duct or ampulla of Vater NENs tended to be diagnosed earlier than patients with primary gallbladder NENs. The median survival times in the NET G1, NET G2, and NEC groups were 167.9, 97.4, and 11.1 months, respectively. A good performance status, absence of distant metastases, and low tumor grade were identified as independent predictors of a favorable prognosis. Conclusion The NET-to-NEC ratio and tumor stage distribution at the diagnosis differed depending on the primary site. Patients with G1 and G2 NETs who underwent surgical resection had good prognoses, whereas those with NEC exhibited more advanced disease and poorer prognoses. The performance status, staging classification, and tumor grade are important factors to consider when devising an appropriate treatment strategy and predicting the prognoses of patients with primary hepatobiliary NEN.

Impact of retention index on the neoadjuvant chemotherapy effect and the prognosis in oesophageal cancer.

OBJECTIVE: The relationship between retention index calculated from dual-time point 18F-fluorodeoxyglucose positron emission tomography-computed tomography and oesophageal cancer prognosis remains unknown. This study aimed to determine usefulness of retention index as a predictor of long-term prognosis of oesophageal cancer and neoadjuvant chemotherapy efficacy. METHODS: A total of 151 patients with oesophageal cancer who underwent esophagectomy were evaluated retrospectively in this study. We acquired positron emission tomography scans 60 and 120 min (SUVmax1 and SUVmax2, respectively) after the intravenous administration of 3.7 Mbq/kg 18F-fluorodeoxyglucose. The patients were divided into two groups: high-retention index (retention index ≥29%, 107 patients) and low-retention index (retention index <29%, 44 patients). Retention index was calculated as follows: retention index (%) = [(SUVmax2 - SUVmax1)/SUVmax1] × 100. RESULTS: The overall survival and relapse-free survival rates in the high-retention index group were significantly lower than those in the low-retention index group (P < 0.001). Our multivariate analysis identified that the high-retention index group contained independent risk factors for overall survival (hazard ratio: 2.44, P = 0.009) and relapse-free survival (hazard ratio: 2.61, P = 0.002). The high-retention index group exhibited a lower partial response rate to neoadjuvant chemotherapy evaluated by computed tomography (P < 0.001) and a lower pathological therapeutic effect in the resected specimen (P = 0.019) than the low-retention index group. CONCLUSIONS: The retention index was associated with neoadjuvant chemotherapy responses and long-term prognosis for oesophageal cancer.