ObjectiveTo investigate the therapeutic effect of paeoniflorin on metabolic dysfunction-associated fatty liver disease （MASLD） combined with insulin resistance （IR）， and to elucidate its regulatory mechanisms on the Toll-like receptor 4 （TLR4）/nuclear transcription factor （NF）-κB-insulin receptor substrate 1 （IRS1） inflammation-insulin signaling axis. MethodsMASLD mouse model was established using a 60% high-fat diet. Mice were randomly assigned to a normal control group， a MASLD model group， and paeoniflorin groups （low dose： 25 mg·kg^-1·d^-1， medium dose： 50 mg·kg^-1·d^-1， high dose： 100 mg·kg^-1·d^-1）， receiving intragastric administration for consecutive 12 weeks. Concurrently， a palmitic acid/oleic acid （PA/OA）-induced lipid deposition model was established in HepG2 cells. Cell counting kit-8 （CCK-8） assay was performed to determine the optimal concentrations of PA/OA and paeoniflorin for intervention. Mice body weight， liver index， and serum levels of alanine aminotransferase （ALT）， aspartate aminotransferase （AST）， triglycerides （TG）， and total cholesterol （TC） were measured. Fasting blood glucose （FBG） and fasting insulin （FINS） levels were measured， and the homeostatic model assessment of insulin resistance （HOMA-IR） was calculated， while an oral glucose tolerance test （OGTT） was performed to evaluate glucose metabolism. Hematoxylin and eosin （HE） staining was used to observe pathological changes and inflammatory cell infiltration in liver tissue， and oil red O staining was used to evaluate lipid droplet deposition in liver tissue and HepG2 cells. Potential targets were screened using network pharmacology and molecular docking. Western blot analysis was performed to detect the expression of HSP90AA1， TLR4， p-NF-κB p65， p-IRS1， and p-Akt proteins in liver tissue and HepG2 cells. ResultsCompared with the normal control group， mice in the MASLD model group exhibited significantly increased body weight， liver index， and serum levels of ALT， AST， TG， and TC， as well as markedly elevated FBG， FINS， and HOMA-IR， and impaired glucose tolerance （P<0.01）. HE staining revealed marked hepatic steatosis and inflammatory cell infiltration， while oil red O staining showed a significant increase in lipid droplet deposition. Compared with the MASLD model group， after intervention with various doses of paeoniflorin， the increase in body weight and liver index was reduced， serum ALT， AST， TG， and TC levels decreased， and FBG， FINS， and HOMA-IR were significantly lowered， with glucose tolerance markedly improved （P<0.05， P<0.01）， showing a certain dose-dependent trend. HE and oil red O staining results showed a marked reduction in hepatic steatosis and lipid deposition. In vitro experiments demonstrated that， compared with the control group， PA/OA treatment significantly induced increased lipid deposition in HepG2 cells. Compared with the model group， paeoniflorin intervention significantly reduced intracellular lipid droplets， and lipid deposition showed a dose-dependent decreasing trend. Mechanism studies indicated that， compared with the normal control group， the MASLD model group exhibited significantly elevated expression of TLR4， HSP90AA1， and p-NF-κB p65， while p-IRS1 （Ser307） expression was elevated and p-Akt （Ser473） expression was reduced （P<0.01）. Compared with the model group， the expression of the aforementioned proteins was significantly reversed in all treatment groups following intervention （P<0.05， P<0.01）. ConclusionPaeoniflorin significantly alleviates lipid deposition and insulin resistance in MASLD mice. Its mechanism of action may involve targeting HSP90AA1， TLR4， and NF-κB1 to regulate the TLR4/NF-κB-IRS1 inflammation-insulin signaling axis. This regulation suppresses inflammatory responses and restores insulin signaling， thereby ameliorating abnormalities in glucose and lipid metabolism.

ObjectiveTo investigate the therapeutic effect of paeoniflorin on metabolic dysfunction-associated fatty liver disease （MASLD） combined with insulin resistance （IR）， and to elucidate its regulatory mechanisms on the Toll-like receptor 4 （TLR4）/nuclear transcription factor （NF）-κB-insulin receptor substrate 1 （IRS1） inflammation-insulin signaling axis. MethodsMASLD mouse model was established using a 60% high-fat diet. Mice were randomly assigned to a normal control group， a MASLD model group， and paeoniflorin groups （low dose： 25 mg·kg^-1·d^-1， medium dose： 50 mg·kg^-1·d^-1， high dose： 100 mg·kg^-1·d^-1）， receiving intragastric administration for consecutive 12 weeks. Concurrently， a palmitic acid/oleic acid （PA/OA）-induced lipid deposition model was established in HepG2 cells. Cell counting kit-8 （CCK-8） assay was performed to determine the optimal concentrations of PA/OA and paeoniflorin for intervention. Mice body weight， liver index， and serum levels of alanine aminotransferase （ALT）， aspartate aminotransferase （AST）， triglycerides （TG）， and total cholesterol （TC） were measured. Fasting blood glucose （FBG） and fasting insulin （FINS） levels were measured， and the homeostatic model assessment of insulin resistance （HOMA-IR） was calculated， while an oral glucose tolerance test （OGTT） was performed to evaluate glucose metabolism. Hematoxylin and eosin （HE） staining was used to observe pathological changes and inflammatory cell infiltration in liver tissue， and oil red O staining was used to evaluate lipid droplet deposition in liver tissue and HepG2 cells. Potential targets were screened using network pharmacology and molecular docking. Western blot analysis was performed to detect the expression of HSP90AA1， TLR4， p-NF-κB p65， p-IRS1， and p-Akt proteins in liver tissue and HepG2 cells. ResultsCompared with the normal control group， mice in the MASLD model group exhibited significantly increased body weight， liver index， and serum levels of ALT， AST， TG， and TC， as well as markedly elevated FBG， FINS， and HOMA-IR， and impaired glucose tolerance （P<0.01）. HE staining revealed marked hepatic steatosis and inflammatory cell infiltration， while oil red O staining showed a significant increase in lipid droplet deposition. Compared with the MASLD model group， after intervention with various doses of paeoniflorin， the increase in body weight and liver index was reduced， serum ALT， AST， TG， and TC levels decreased， and FBG， FINS， and HOMA-IR were significantly lowered， with glucose tolerance markedly improved （P<0.05， P<0.01）， showing a certain dose-dependent trend. HE and oil red O staining results showed a marked reduction in hepatic steatosis and lipid deposition. In vitro experiments demonstrated that， compared with the control group， PA/OA treatment significantly induced increased lipid deposition in HepG2 cells. Compared with the model group， paeoniflorin intervention significantly reduced intracellular lipid droplets， and lipid deposition showed a dose-dependent decreasing trend. Mechanism studies indicated that， compared with the normal control group， the MASLD model group exhibited significantly elevated expression of TLR4， HSP90AA1， and p-NF-κB p65， while p-IRS1 （Ser307） expression was elevated and p-Akt （Ser473） expression was reduced （P<0.01）. Compared with the model group， the expression of the aforementioned proteins was significantly reversed in all treatment groups following intervention （P<0.05， P<0.01）. ConclusionPaeoniflorin significantly alleviates lipid deposition and insulin resistance in MASLD mice. Its mechanism of action may involve targeting HSP90AA1， TLR4， and NF-κB1 to regulate the TLR4/NF-κB-IRS1 inflammation-insulin signaling axis. This regulation suppresses inflammatory responses and restores insulin signaling， thereby ameliorating abnormalities in glucose and lipid metabolism.

Objective:To evaluate the short-term efficacy of endoscopic-laparoscopic regional gastric resection combined with sentinel lymph node basin dissection in patients with early-stage gastric cancer.Methods:This is a retrospective case series study. Data of 17 consecutive early gastric cancer patients from a prospective cohort at Beijing Friendship Hospital,Capital Medical University were analyzed between August 2023 and August 2024. Sixteen cases were from the department of general surgery and 1 from the department of gastroenterology. The cohort included 9 males and 8 females,with a mean age of 61.4 years (range: 46 to 79 years). Clinical data,including demographics,pathological features,surgical procedures,and follow-up outcomes,were collected through medical records and databases. All patients were followed for over 3 months,with follow-up ending on December 5,2024.Results:A total of 17 patients were involved. Among them, 5 patients underwent endoscopic submucosal dissection (ESD) combined with laparoscopic sentinel lymph node dissection (LSBD),and another 3 patients who underwent complete ESD resection received LSBD due to pathological stage meeting the expanded indications. 6 patients who underwent non-curative ESD resection received laparoscopic gastric regional resection (LRG) combined with LSBD,and another 3 patients directly received LRG combined with LSBD. The average number of sentinel lymph nodes dissected before surgery ( M(IQR)) was 8.9 (4.5) (range: 4 to 21),and the detection rate and accuracy rate were both 100%. Postoperative pathology confirmed that there was no metastasis in the sentinel lymph nodes of 5 patients who underwent ESD combined with LSBD and 3 patients who underwent LSBD after complete ESD resection. The vertical and horizontal margins of ESD were all negative. One patient was an absolute indication for ESD. For the 6 patients who underwent non-curative ESD resection combined with LRG and LSBD,the horizontal margins were all negative. Two patients showed 1 metastasis in each of the 21 and 9 sentinel lymph nodes during the operation,and additional distal gastrectomy was performed during the operation. Postoperatively,73 and 39 lymph nodes were retrieved respectively. The former had 1 additional metastasis,while the latter had no metastasis. Among the 3 patients who underwent direct LRG combined with LSBD,the horizontal margins were negative. One patient was confirmed as an absolute indication for ESD by postoperative pathology,and one patient had 1 metastasis in 8 sentinel lymph nodes during the operation,and additional distal gastrectomy was performed. Postoperatively,there was no metastasis in 54 lymph nodes. All patients had no complications such as infection,bleeding,perforation,or death after surgery. Among the 14 patients who did not receive additional radical surgery,they were able to pass gas and defecate within 3 days after surgery,with an average hospital stay of 6 days. The nutritional indicators and gastric radionuclide emptying imaging half-emptying time were similar to those before surgery at 3 months after surgery. Conclusions:Laparoscopic and endoscopic cooperative regional gastrectomy with sentinel lymph node basin dissection has the advantages of minimal invasiveness,preservation of gastric function,and precise treatment. It maybe suitable for patients with early-stage gastric cancer at high risk of lymph node metastasis and has good short-term efficacy.

Objective To investigate the cIinicopathological features and immunohistochemical expression of gastric hyperplastic polyps(GHPs)with dysplasia/adenocarcinoma.Methods A retrospective analysis of 24 cases(44 polyps)that were diagnosed as GHPs with dysplasia/adenocarcinoma in our hospital from January 2020 to December 2024 was reviewed,and clinical,histomorphological,immunophenotypic and follow-up data were analyzed.Results There were 20 female and 4 male cases,with a mean age of(65.5±7.9)(range 56～76)years.Among 44 polyps,3 occurred in the antrum of the stomach,1 in the gastric horn,and 40 in the fundus/body.Among the polyps,32 cases were diagnosed as high-grade dysplasia,4 cases as low-grade dysplasia,4 cases as coexistence of low-grade+high-grade dysplasia,2 cases as mucinous adenocarcinoma,1 cases as poorly differentiated adenocarcinoma,and 1 cases as signet-ring cell carcinoma.The histological manifestations of 23 cases of background mucosa were autoimmune metaplastic atrophic gastritis(AMAG).the P53 of 8 polyps showed a mutant expression pattern.Through MUC5/MUC6/MUC2/CD10 joint examination,33 cases showed gastric type(25 cases of which were foveal epithelium type),4 cases were intestinal type,5 cases were mixed gastrointestinal type,and 2 cases were non-gastrointestinal type.Conclusion The neoplastic transformation of GHPs is closely related to AMAG.It is necessary for clinicians and pathologists to strengthen their evaluation of background mucosa,to achieve early detection,early diagnosis and early treatment.

Objective:To explore the diagnostic efficacy of methylene blue staining combined with light transmission method (termed as light transmission and staining) in endoscopic submucosal dissection (ESD) specimens of early gastric cancer.Methods:A retrospective study was conducted on 75 specimens of early gastric cancer treated with ESD at Beijing Friendship Hospital, Capital Medical University from October 2021 to August 2023. Under a stereomicroscope, magnified observation and transmitted light transmission and staining observation were performed to compare the demarcation line (DL), irregular microvascular pattern (IMVP) and irregular microsurface pattern (IMSP) of the lesion, and the differences among histological types were compared. Furthermore, the false positive rate of surgical margin, the detection rate of undifferentiated cancer and multifocal lesions were compared against the 88 controls processed by traditional method.Results:Using the light transmission and staining method, DL, IMVP and IMSP were detected in 96.0% (72/75), 89.3% (67/75), and 98.7% (74/75), which was higher than 72.0% (54/75), 6.7% (5/75), and 26.7% (20/75) by using the magnified observation ( χ 2=8.036, P<0.001; χ 2=0.640, P<0.001; χ 2=0.369, P<0.001). There was no statistical difference in the coincidence rate of endoscopy and pathology between differentiated type, undifferentiated type and mixed type [92.2% (59/64), 50.0% (1/2), 77.8% (7/9), χ 2=5.145, P=0.055]. Compared to traditional methods, light transmission and staining could increase the detection rate of undifferentiated cancer [14.7% (11/75) VS 4.5% (4/88), χ 2=4.964, P=0.026] and reduce the false positive rate of surgical margins [1.3% (1/75) VS 11.4% (10/88), χ 2=4.585, P=0.032], but showed no statistical difference in the detection rate of multifocal lesions [5.3% (4/75) VS 0.0% (0/88), χ 2=2.841, P=0.094]. Conclusion:Light transmission and staining enhances pathological recognition of DL, IMVP and IMSP during specimen processing, improving detection of undifferentiated cancer and reducing false positive of margin.

Objective To investigate the cIinicopathological features and immunohistochemical expression of gastric hyperplastic polyps(GHPs)with dysplasia/adenocarcinoma.Methods A retrospective analysis of 24 cases(44 polyps)that were diagnosed as GHPs with dysplasia/adenocarcinoma in our hospital from January 2020 to December 2024 was reviewed,and clinical,histomorphological,immunophenotypic and follow-up data were analyzed.Results There were 20 female and 4 male cases,with a mean age of(65.5±7.9)(range 56～76)years.Among 44 polyps,3 occurred in the antrum of the stomach,1 in the gastric horn,and 40 in the fundus/body.Among the polyps,32 cases were diagnosed as high-grade dysplasia,4 cases as low-grade dysplasia,4 cases as coexistence of low-grade+high-grade dysplasia,2 cases as mucinous adenocarcinoma,1 cases as poorly differentiated adenocarcinoma,and 1 cases as signet-ring cell carcinoma.The histological manifestations of 23 cases of background mucosa were autoimmune metaplastic atrophic gastritis(AMAG).the P53 of 8 polyps showed a mutant expression pattern.Through MUC5/MUC6/MUC2/CD10 joint examination,33 cases showed gastric type(25 cases of which were foveal epithelium type),4 cases were intestinal type,5 cases were mixed gastrointestinal type,and 2 cases were non-gastrointestinal type.Conclusion The neoplastic transformation of GHPs is closely related to AMAG.It is necessary for clinicians and pathologists to strengthen their evaluation of background mucosa,to achieve early detection,early diagnosis and early treatment.

Objective:To explore the diagnostic efficacy of methylene blue staining combined with light transmission method (termed as light transmission and staining) in endoscopic submucosal dissection (ESD) specimens of early gastric cancer.Methods:A retrospective study was conducted on 75 specimens of early gastric cancer treated with ESD at Beijing Friendship Hospital, Capital Medical University from October 2021 to August 2023. Under a stereomicroscope, magnified observation and transmitted light transmission and staining observation were performed to compare the demarcation line (DL), irregular microvascular pattern (IMVP) and irregular microsurface pattern (IMSP) of the lesion, and the differences among histological types were compared. Furthermore, the false positive rate of surgical margin, the detection rate of undifferentiated cancer and multifocal lesions were compared against the 88 controls processed by traditional method.Results:Using the light transmission and staining method, DL, IMVP and IMSP were detected in 96.0% (72/75), 89.3% (67/75), and 98.7% (74/75), which was higher than 72.0% (54/75), 6.7% (5/75), and 26.7% (20/75) by using the magnified observation ( χ 2=8.036, P<0.001; χ 2=0.640, P<0.001; χ 2=0.369, P<0.001). There was no statistical difference in the coincidence rate of endoscopy and pathology between differentiated type, undifferentiated type and mixed type [92.2% (59/64), 50.0% (1/2), 77.8% (7/9), χ 2=5.145, P=0.055]. Compared to traditional methods, light transmission and staining could increase the detection rate of undifferentiated cancer [14.7% (11/75) VS 4.5% (4/88), χ 2=4.964, P=0.026] and reduce the false positive rate of surgical margins [1.3% (1/75) VS 11.4% (10/88), χ 2=4.585, P=0.032], but showed no statistical difference in the detection rate of multifocal lesions [5.3% (4/75) VS 0.0% (0/88), χ 2=2.841, P=0.094]. Conclusion:Light transmission and staining enhances pathological recognition of DL, IMVP and IMSP during specimen processing, improving detection of undifferentiated cancer and reducing false positive of margin.

Objective:To evaluate the short-term efficacy of endoscopic-laparoscopic regional gastric resection combined with sentinel lymph node basin dissection in patients with early-stage gastric cancer.Methods:This is a retrospective case series study. Data of 17 consecutive early gastric cancer patients from a prospective cohort at Beijing Friendship Hospital,Capital Medical University were analyzed between August 2023 and August 2024. Sixteen cases were from the department of general surgery and 1 from the department of gastroenterology. The cohort included 9 males and 8 females,with a mean age of 61.4 years (range: 46 to 79 years). Clinical data,including demographics,pathological features,surgical procedures,and follow-up outcomes,were collected through medical records and databases. All patients were followed for over 3 months,with follow-up ending on December 5,2024.Results:A total of 17 patients were involved. Among them, 5 patients underwent endoscopic submucosal dissection (ESD) combined with laparoscopic sentinel lymph node dissection (LSBD),and another 3 patients who underwent complete ESD resection received LSBD due to pathological stage meeting the expanded indications. 6 patients who underwent non-curative ESD resection received laparoscopic gastric regional resection (LRG) combined with LSBD,and another 3 patients directly received LRG combined with LSBD. The average number of sentinel lymph nodes dissected before surgery ( M(IQR)) was 8.9 (4.5) (range: 4 to 21),and the detection rate and accuracy rate were both 100%. Postoperative pathology confirmed that there was no metastasis in the sentinel lymph nodes of 5 patients who underwent ESD combined with LSBD and 3 patients who underwent LSBD after complete ESD resection. The vertical and horizontal margins of ESD were all negative. One patient was an absolute indication for ESD. For the 6 patients who underwent non-curative ESD resection combined with LRG and LSBD,the horizontal margins were all negative. Two patients showed 1 metastasis in each of the 21 and 9 sentinel lymph nodes during the operation,and additional distal gastrectomy was performed during the operation. Postoperatively,73 and 39 lymph nodes were retrieved respectively. The former had 1 additional metastasis,while the latter had no metastasis. Among the 3 patients who underwent direct LRG combined with LSBD,the horizontal margins were negative. One patient was confirmed as an absolute indication for ESD by postoperative pathology,and one patient had 1 metastasis in 8 sentinel lymph nodes during the operation,and additional distal gastrectomy was performed. Postoperatively,there was no metastasis in 54 lymph nodes. All patients had no complications such as infection,bleeding,perforation,or death after surgery. Among the 14 patients who did not receive additional radical surgery,they were able to pass gas and defecate within 3 days after surgery,with an average hospital stay of 6 days. The nutritional indicators and gastric radionuclide emptying imaging half-emptying time were similar to those before surgery at 3 months after surgery. Conclusions:Laparoscopic and endoscopic cooperative regional gastrectomy with sentinel lymph node basin dissection has the advantages of minimal invasiveness,preservation of gastric function,and precise treatment. It maybe suitable for patients with early-stage gastric cancer at high risk of lymph node metastasis and has good short-term efficacy.

Purpose To investigate the clinical feature and histopathology of pyloric gland adenoma.Methods Clinical da-ta of 16 cases of pyloric adenomas were collected.The expres-sion of Pepsinogen I,p53,MUC6,MUC5AC,CgA,Syn,CD56,Ki67,CDX-2,MUC2,β-catenin,and CD10 was detec-ted by immunohistochemistry EnVision method.The relationship with clinicopathological features and prognosis was analyzed.Results There were 7 males and 9 females,aged from 26 to 81 years with an average of 58 years.Tumor diameters ranged from 0.2 to 4 centimeter with a mean of 1.3 centimeter.The anatomi-cal sites of the 16 PGA were stomach(6 cases),including 3 ca-ses in body,3 cases in fundus and duodenum(3 cases).7 ca-ses of low-grade PGAs were composed of closely packed pyloric-type glands,lined by cuboidal/low columnar epithelia.The nu-clei(round to ovoid)were basally located,with inconspicuous nucleoli.Neoplastic cells characterized by a defined ground-glass appearance,with clear or eosinophilic cytoplasm.The cell was lack of a well-defined apical mucin cap.1 case of high-grade PGAs consistently exhibited architecture,crowded nuclei,and loss of nuclear polarity.The remaining 8 cases had both low-and high-grade components.Squamous morula was found in 5 cases.According to immunohistochemical characteristics,8 of 16 cases were mixed pattern(MUC5AC+,MUC6+).Others were pure pyloric type(MUC5AC-,MUC6+).No foveolar-dominant type(MUC5AC+,MUC6-)was found.Conclusion PGA is a rare tumor of the digestive system,with characteristic morpholog-ical characteristics and immunophenotype.Clinicians and pathol-ogists need to strengthen their understanding and better manage patients because of the risk of malignant transformation.Early detection,early diagnosis and early treatment are needed.

Objective:To investigate the application value of magnetic resonance imaging(MRI) in evaluating the efficacy of anti-PD-1 combined with neoadjuvant therapy for microsatellite stability (MSS)/proficient mismatch repair (pMMR) locally advanced rectal cancer (LARC).Methods:The prospective single-arm phase Ⅱ study was conducted. The clinicopathological data of 37 patients with MSS/pMMR LARC who were admitted to Beijing Friendship Hospital of Capital Medical University from April 2021 to September 2022 were collected. All patients underwent anti-PD-1 combined with neoadjuvant therapy and radical total mesorectal excision. Observation indicators: (1) enrolled pati-ents; (2) MRI and pathological examination; (3) concordance analysis of MRI examination reading; (4) evaluation of MRI examination. Measurement data with normal distribution were represented as Mean± SD. Count data were expressed as absolute numbers or percentages. Linear weighted κ value was used to evaluate the concordance of radiologist assessment. Sensitivity, negative predictive value, accuracy, overstaging rate and understaging rate were used to evaluate the predictive value. Results:(1) Enrolled patients. A total of 37 eligible patients were screened out, including 21 males and 16 females, aged (61±11)years. MRI examination was performed before and after combined therapy, and pathological examination was performed after radical resection. (2) MRI and pathological examination of patients. Among the 37 patients, MRI before combined therapy showed 0, 0, 5, 24 and 8 cases in stage T0, T1, T2, T3 and T4, 10, 17 and 10 cases in stage N0, N1 and N2, 28 and 9 cases of positive and negative extramural vascular invasion (EMVI), 4 and 33 cases of positive and negative mesorectal fascia (MRF), respectively. MRI examination after combined therapy showed 15, 4, 7, 10 and 1 cases in stage T0, T1, T2, T3 and T4, 34, 2 and 1 cases in stage N0, N1 and N2, 9 and 28 cases of positive and negative EMVI, 1 and 36 cases of positive and negative MRF. There were 16, 13, 8 and 0 cases of tumor regression grading (TRG) 0, 1, 2 and 3, respectively. Postoperative pathological examination showed 18, 4, 3, 11, 1 cases in stage T0, T1, T2, T3, T4, 33, 3, 1 cases in stage N0, N1, N2, positive and negative EMVI and unknown data in 1, 35, 1 cases, positive and negative circumferential margin in 0 and 37 cases, grade 0, grade 1, grade 2, grade 3 of American Joint Committee on Cancer TRG in 18, 9, 8, 2 cases, respectively. Pathological complete response rate was 48.6%(18/37) and approximate pathological complete response rate was 24.3%(9/37). (3)Concordance analysis of MRI examination reading. The κ value of T staging and N staging on MRI before combined therapy was 0.839 ( P<0.05) and 0.838 ( P<0.05), respectively. The κ value of T staging and N staging on MRI after combined therapy was 0.531 ( P<0.05) and 0.846 ( P<0.05), respectively. The κ value of EMVI and MRF was 0.708 ( P<0.05) and 0.680 ( P<0.05) before combined therapy, and they were 0.561 ( P<0.05) and 1.000 ( P<0.05) after combined therapy, respectively. The κ value of TRG 3-round reading for TRG was 0.448 ( P<0.05). (4) Evaluation of MRI examination. ① MRI evaluation of T and N staging. The accuracy of MRI examination after combined therapy for distinguishing stage T0 was 75.7%[28/37, 95% confidence interval ( CI) as 62.2%-89.2%], the understaging rate was 8.1%(3/37, 95% CI as 0-18.9%), the overstaging rate was 16.2%(6/37, 95% CI as 5.4%-29.7%). The accuracy of MRI examination for distinguishing stage T0-T2 was 86.5%(32/37, 95% CI as 73.0%-97.3%), its understaging rate and overstaging rate were 8.1%(3/37, 95% CI as 0-18.9%) and 5.4% (2/37, 95% CI as 0-13.5%), respectively. The accuracy of MRI examination for distinguishing N staging was 91.9%(34/37, 95% CI was 81.1%-100.0%), its understaging rate and overstaging rate were 5.4%(2/37, 95% CI as 0-13.5%) and 2.7%(1/37, 95% CI as 0-8.1%), respectively. Among 18 patients in pathological stage T0, the overstaging rate of MRI was 33.3%(6/18). All the 4 patients in pathological stage T1 and 3 pati-ents in pathological stage T2 had correct diagnosis. There were 3 cases with understaging among 12 patients in pathological stage T3-T4. Among the 37 patients in pathological stage N0-N2, 34 cases had correct diagnosis, 1 case was overstaged as stage N1 due to a round mesorectal lymph node with short diameter as 6 mm, and 2 cases were diagnosed as stage N0 due to the small lymph nodes with the maximum short diameter as 3 mm. ② MRI evaluation of EMVI and MRF. The accuracy, sensitivity and negative predictive value of MRI for evaluating EMVI were 86.5%(32/37, 95% CI as 75.0%-97.2%), 100.0% and 100.0%, respectively, and the overestimation rate of EMVI was 13.9%(5/36, 95% CI as 2.8%-25.0%), and no underestimation occurred. Of 35 pathologically negative EMVI patients, a rate of 14.3%(5/35) of patients were positive on MRI. The main reason for overestaging was that thickened fibrous tissue outside the rectal wall was mistaken for vascular invasion. The accuracy of MRI for evaluating MRF was 97.3%(36/37, 95% CI as 91.9%-100.0%), and 1 case (1/37, 2.7%, 95% CI as 0-8.1%) was overestimated as positive MRF due to misdiagnosis of pararectal MRF lymph nodes. The negative predictive value of MRI for assessing MRF was 100.0%. ③ MRI evaluation of TRG. The accuracy, understaging and overstaging rates of MRI for evaluating pathological TRG 0 were 78.4%(29/37, 95% CI as 64.9%-91.9%), 8.1%(3/37, 95% CI as 0-18.9%), 13.5%(5/37, 95% CI as 5.4%-27.0%), respectively. The accuracy, understaging and overstaging rates of MRI for evaluating pathological TRG 0-1 were 89.2%(33/37, 95% CI as 78.4%-97.3%), 8.1%(3/37, 95% CI as 0-18.9%), 2.7%(1/37, 95% CI as 0-8.1%), respectively. Of the 18 patients with pathologic complete response, 5 cases were diagnosed as pathological TRG 1 and 13 cases as pathological TRG 0. One near-pCR patient was assessed as pathological TRG 2. Two patients with pathological TRG 3 were incorrectly diagnosed on MRI. Conclusions:Anti-PD-1 combined with neoadjuvant therapy can downstage the LARC pati-ents with MSS/pMMR. MRI is effective in predicting T staging, N staging, EMVI, MRF and TRG. However, overstaging should be prevented.