Lynch syndrome (LS) is an autosomal dominant cancer predisposition syndrome, associated with substantially increased risks of colorectal and gynecologic malignancies. Endometrial cancer may serve as a sentinel cancer for LS, placing gynecologists and gynecologic oncologists in a key position for early recognition and long-term management. This joint statement was developed through a multidisciplinary process involving the Japan Society of Gynecologic Oncology, the Japan Society of Clinical Oncology, the Japanese Society of Hereditary Tumors, and the Japanese Society for Cancer of the Colon and Rectum. It aims to clarify the clinical utility of diagnosing LS in gynecologic oncology within the Japanese healthcare system. We outline a tumor-first paradigm in which universal mismatch repair immunohistochemistry and/or microsatellite instability testing for endometrial cancer facilitates LS detection and provides actionable biomarkers for systemic therapy. This statement summarizes the clinical impact of LS diagnosis across gynecologic oncology. We highlight patterns of synchronous and metachronous malignancies and the prevalence of LS in ovarian cancer, particularly in endometrioid and clear-cell subtypes. We discuss surgical implications, including risk-reducing hysterectomy with bilateral salpingo-oophorectomy, consideration of concomitant gynecologic risk-reducing surgery during colorectal cancer resection, and individualized ovarian preservation in selected early-stage endometrial cancer or atypical endometrial hyperplasia. We also review the treatment relevance of deficient mismatch repair/microsatellite instability-high status for immune checkpoint inhibitors and emerging fertility-preserving approaches, and address surveillance, cascade testing for relatives, implementation barriers, and the need for multidisciplinary pathways and healthcare system-level support to ensure equitable access to genetic counseling and testing.

To investigate whether colorectal cancer (CRC) sidedness is associated with intraoperative lavage cytology results, tumor recurrence, and prognosis. Using data from a multicenter prospective observational study conducted by the Japanese Society for Cancer of the Colon and Rectum (JSCCR), we retrospectively analyzed prognosis and recurrence patterns in pathological stage II/III right-sided and left-sided CRC, stratified by positive versus negative lavage cytology results. A total of 1500 patients met the inclusion criteria and were enrolled. Of these, 534 had right-sided CRC and 966 had left-sided CRC. Fifty-nine patients (3.9

Robotic surgery is increasingly adopted for rectal cancer management, including selected patients with locally advanced disease. We evaluated perioperative safety and medium- to long-term outcomes after robot-assisted rectal cancer surgery with multivisceral resection for cT4 rectal cancer in a single high-volume center. We retrospectively reviewed 45 consecutive patients with locally advanced rectal cancer who underwent robot-assisted surgery with multivisceral resection between April 2021 and June 2025. Demographic and clinical variables, surgical and postoperative outcomes, and pathological findings were extracted from medical records. Recurrence-free survival (RFS), overall survival, and local recurrence were assessed. The study included 45 patients (19 females) with a median age of 72 years. Postoperative complications of Clavien–Dindo grade III or higher occurred in 4 patients (8.8

INTRODUCTION:Factor XIII deficiency (FXIIID) is a rare coagulation disorder that can cause severe or delayed bleeding and impair wound healing despite normal routine coagulation test results. Congenital FXIIID is caused by homozygous germline pathogenic variants of F13A or F13B. Herein, we report the successful treatment of a patient with FXIIID who underwent surgery for juvenile polyposis syndrome (JPS)-associated early gastric cancer. CASE PRESENTATION:A 44-year-old woman was admitted to the hospital with anemia secondary to menorrhagia. Gastrointestinal examination revealed polyposis throughout the stomach and type 0-Is early gastric cancer, which was consistent with the histological diagnosis of the biopsy specimens. Investigation into her family history revealed that her mother and maternal aunt had gastric polyposis. Preoperative laboratory tests were almost normal, except for low levels of hemoglobin (6.0 g/dL) and Factor XIII (FXIII) activity (31%). Robot-assisted total gastrectomy with D1-level lymph node dissection, followed by Roux-en-Y reconstruction, was successfully performed, with an operative time of 347 min and estimated blood loss of 26 mL. To prevent surgery-related bleeding, preoperative and postoperative administration of FXIII concentrate (30 IU/kg) was planned. The postoperative course was uneventful, and the patient was discharged on POD 9. Genetic testing identified a germline pathogenic frameshift variant in SMAD4 (c.96delT [p.Ser32fs*13]), which was consistent with the phenotype of JPS, and a heterozygous missense variant of uncertain significance in F13A1 (c.308A>T [p.Glu103Val]). Nine months postoperatively, FXIII activity was re-evaluated and remained low at 59%, although it was higher than the preoperative level. CONCLUSIONS:Recognition of FXIIID and appropriate perioperative management may help prevent unexpected bleeding and enable safe gastrectomy in patients with FXIIID.

Aim : This study aimed to clarify whether tumor sidedness in colorectal cancer (CRC) influences intraoperative lavage cytology findings, recurrence patterns, and long-term outcomes. Methods : We performed a secondary analysis of a multicenter prospective dataset collected by the Japanese Society for Cancer of the Colon and Rectum (JSCCR). Patients with pathological stage II/III CRC were categorized by tumor sidedness and lavage cytology status, and survival outcomes and recurrence patterns were compared. This study adhered to the STROBE guidelines for reporting (checklist provided). Results : Among 1,500 eligible patients, 534 had right-sided and 966 had left-sided CRC. Positive lavage cytology was identified in 59 patients (3.9%). In recurrent cases, right-sided tumors were more frequently associated with peritoneal relapse (p = 0.04). In the cytology-negative cohort, right-sided CRC showed a higher 5-year relapse-free survival (RFS) rate than left-sided CRC (79.6% vs. 73.4%, p = 0.01), whereas overall survival (OS) was comparable (89.2% vs. 87.7%, p = 0.52). In the cytology-positive cohort, no statistically significant differences in RFS or OS were observed between tumor locations. However, among patients who developed recurrence, right-sided CRC was associated with significantly worse survival after recurrence (p = 0.04). Conclusion : Tumor sidedness impacts recurrence behavior and prognosis in CRC, particularly in relation to cytology status. Right-sided CRC with positive cytology was characterized by frequent peritoneal recurrence and poor post-recurrence survival.

BACKGROUND:Germline pathogenic variants (GPVs) in cancer predisposition genes increase cancer risk, but their population-level prevalence in Japan remains unclear. AIM:To estimate the prevalence of GPV carriers of hereditary cancer predisposition syndromes (HCPSs) in the Japanese population. DATA SOURCE AND METHODS:A cross-sectional analysis of the Tohoku Medical Megabank Organization datasets was conducted to assess allele frequencies of rare GPVs, estimate carrier prevalence, and describe variant distribution. RESULTS:The cumulative allele frequency of rare GPVs of cancer predisposing genes was 1.47% for autosomal dominant and 3.20% for autosomal recessive diseases. The estimated prevalence of GPV carriers was 2.90% (1 in 35 individuals) and 0.10% (1 in 977 individuals) for autosomal dominant HCPSs and autosomal recessive HCPSs, respectively; ~6.19% of the population (1 in 16 individuals) were carriers. Variant types differed across genes, and hotspot variants had a significant impact on allele frequencies. Moreover, 47 structural variants (0.28%) having the potential to cause structural disruption were identified. CONCLUSIONS:Allele frequency analysis of rare GPVs of cancer predisposition genes offered valuable insight into the prevalence of GPV carriers of HCPSs in the Japanese population. Hotspot variants may represent founder mutations within specific ethnic groups, and their presence or absence could affect gene-specific allele frequencies.

Objectives: Colorectal cancer (CRC) with synchronous peritoneal metastasis is considered to have a worse prognosis. Although macroscopic complete resection is associated with a favorable prognosis, the prognostic determinants in this population remain poorly characterized. Therefore, it is crucial to identify prognostic factors following macroscopic complete resection to determine optimal care strategies that improve patient outcomes and to predict prognosis. Methods: In a multi-institute cohort study, we prospectively assessed clinicopathological factors that affect prognosis in 36 patients with CRC and synchronous peritoneal metastasis who underwent macroscopic complete resection. Results: 26 of 36 patients (72%) developed recurrence during follow-up, with a median of 34 months. Peritoneum was the most common site of recurrence. In survival analysis, patients with low preoperative serum CA19-9 levels had a favorable overall survival compared with those with high preoperative serum CA19-9 levels (HR: 0.42, 95% CI: 0.15-1.21, P=0.044). Also, patients with right-sided CRC had more favorable overall survival than those with left-sided CRC (HR: 0.44, 95% CI: 0.18-1.06, P=0.047). Furthermore, right-sided CRC with low preoperative serum CA19-9 levels was associated with significantly better overall survival than those with high preoperative serum CA19-9 levels or left-sided CRC (HR: 0.17, 95% CI: 0.07-0.41, P<0.001). Conclusions: In this prospective multi-institutional cohort of CRC patients with synchronous peritoneal metastasis undergoing macroscopic complete resection, recurrence was frequent, predominantly involving the peritoneum. Integrating tumor biology (sidedness) and serum biomarkers (CA19-9) may enhance prognostic stratification and guide individualized management strategies in this high-risk population.

Objectives: Familial adenomatous polyposis (FAP) is an inherited disorder characterized by multiple colorectal polyposis and is frequently associated with a variety of extracolonic lesions. However, neoplastic lesions of the biliary tract system, excluding those of the ampulla of Vater, are extremely rare in FAP, and the impact of APC alterations on their tumorigenesis remains unclear. We aimed to clarify the relationship between germline variants and somatic variants in the APC gene in biliary tract neoplasms (BTNs) of FAP patients. Methods: A total of 115 genetically confirmed FAP cases treated at our department between 1997 and 2024 were investigated regarding development of BTNs. APC gene analysis was performed in the BTNs. Results: Of 115 FAP cases, three developed BTNs. Case 1 was a 69-year-old female who underwent subtotal stomach-preserving pancreaticoduodenectomy for duodenal and middle bile duct carcinoma. Case 2 was a 67-year-old female who underwent pancreaticoduodenectomy for gastric, duodenal, and upper bile duct carcinoma. Case 3 was a 47-year-old male who underwent pancreas-sparing total duodenectomy with cholecystectomy for Spigelman Stage IV duodenal polyposis and gallbladder polyposis. In addition to germline pathogenic variants, somatic pathogenic variants of APC were identified in all the BTNs. Conclusions: These findings suggest that the APC two-hit theory may underlie the tumorigenesis of these rare BTNs, consistent with the pathogenic process observed in colonic and other extracolonic lesions in patients with FAP.

Background: Owing to significant clinical heterogeneity, the achievement of accurate survival forecasting for individuals with colorectal cancer and peritoneal metastasis continues to be a complex undertaking. We aimed to transcend traditional prognostic limitations by evaluating machine learning boosting models against standard regression-based methods in terms of estimating overall survival (OS). Methods: Utilizing a multi-institutional registry of 150 patients diagnosed with synchronous peritoneal metastasis of colorectal cancer, we integrated 124 clinicopathological variables to refine our predictive models. Beyond standard preprocessing—including standardization and median imputation—we rigorously compared XGBoost and LightGBM against Ridge, Lasso, and linear regression via five-fold cross-validation. To specifically address right-censoring, an XGBoost Cox model was implemented and validated using Harrell’s C-index, with SHAP and LIME providing essential model interpretability. Results: Boosting models consistently outperformed linear alternatives, which struggled with high error rates and negative R2 values. Specifically, XGBoost achieved an MAE of 475 ± 60 and an RMSE of 585 ± 88. The XGBoost Cox model reached a C-index of 0.64 ± 0.06. SHAP analysis highlighted inflammatory markers and peritoneal disease extent as the most influential prognostic drivers. Conclusions: While boosting models offer a clear accuracy advantage over linear methods, their prognostic power remains moderate. These findings underscore the potential of ensemble learning in oncology, yet mandate external validation before these tools can be integrated into clinical decision-making.

Epidermal growth factor receptor (EGFR) blockade combined with cytotoxic chemotherapy has substantially improved outcomes in unresectable metastatic colorectal cancer (mCRC), particularly in patients with left-sided RAS wild-type disease [...]

We previously identified T4, an undifferentiated histological type, and positive lymph node (LN) metastasis as risk factors for positive intraperitoneal lavage cytology (IPLC) in colorectal cancer (CRC) surgery. However, the number of LN metastases influencing IPLC positivity remains unknown. We conducted a multicenter, prospective, observational study to determine the threshold number of LN metastases associated with IPLC positivity and identify patients with CRC who should undergo IPLC. Patients with clinical stage II and III CRC who underwent tumor resection and IPLC between 2013 and 2017 were included. IPLC was performed once during laparotomy and once after tumor resection. Patients with a T4 stage, ascites, or undifferentiated types were excluded, as these factors affected IPLC. The number of LNs that influenced IPLC positivity was examined using a logistic regression analysis and the Akaike information criterion (AIC). The IPLC positivity rate was 2.0

Approximately 5% of all colorectal cancers have a strong genetic component and are classified as hereditary colorectal cancer (HCRC). Some of the unique features commonly seen in HCRC cases include early age of onset, synchronous/metachronous cancer occurrence, and multiple cancers in other organs. These characteristics require different management approaches, including diagnosis, treatment or surveillance, from those used in the management of sporadic colorectal cancer. Accurate diagnosis of HCRC is essential because it enables targeted surveillance and risk reduction strategies that improve patient outcomes. Recent genetic advances revealed several causative genes for polyposis and non-polyposis syndromes. The Japanese Society for Cancer of the Colon and Rectum (JSCCR) first published guidelines for the management of HCRC in 2012, with subsequent revisions every 4 years. The 2024 update to the JSCCR guidelines for HCRC was developed by meticulously reviewing evidence from systematic reviews and the consensus of the JSCCR HCRC Guidelines Committee, which includes representatives from patient advocacy groups for FAP and Lynch syndrome. These guidelines provide an up-to-date summary of HCRC, along with clinical recommendations for managing FAP and Lynch syndrome.

Aim:Spigelman stage IV duodenal polyposis (SP-stage IV DP) is associated with high duodenal cancer risk in patients with familial adenomatous polyposis (FAP). This study evaluated the surgical and oncological outcomes of pancreas-sparing total duodenectomy (PSTD) as a surgical prophylaxis for severe duodenal polyposis in FAP. Methods:Medical records were reviewed to evaluate factors concerning short- and long-term clinical and oncological outcomes in consecutive patients with FAP who underwent PSTD for SP-stage IV DP. Results:There were twenty-seven patients (median age: 48 years) from 26 families, of whom 12 were female. Clavien-Dindo grade IIIa/IIIb complications included delayed gastric emptying (n = 14) and pancreatic fistula (n = 10); no mortalities were observed. Histopathological examinations revealed no malignant neoplasms deeper than T1a in the duodenum and ampulla. Follow-up (median 6.4 years) revealed anastomotic stricture of the reconstructed neo-common channel (n = 5), anastomotic ulcer of the gastrojejunostomy site (n = 5), acute pancreatitis (n = 4), and acute cholangitis (n = 2), all of which were successfully treated endoscopically or conservatively. Malignant neoplasms after PSTD included gastric cancer (n = 3), remnant ano-rectal cancer (n = 3), ileal cancer (n = 1), ileal pouch cancer (n = 1), and endometrial cancer (n = 1). The cumulative 10-year survival rate following PSTD was 87.4%. Conclusions:PSTD for the prophylactic management of SP-stage IV DP was associated with notable but manageable postoperative morbidity. Long-term surveillance remains essential for the development of extraduodenal malignancies to confirm the oncological efficacy of this type of surgery.

219 Background: Epidermal growth factor receptor (EGFR) blockade can effectively shrink tumors in metastatic colorectal cancer (CRC) patients without RAS nor BRAF mutations. However, some patients without RAS nor BRAF mutations in their primary tumors have them in metastatic tumors (heterogeneity). Circulating tumor DNA (ctDNA) can reflect these mutations in metastatic tumors. Here, we evaluated the efficacy of EGFR blockade in patients who had no RAS nor BRAF mutations in their primary tumors, but who had them in ctDNA. Methods: We prospectively enrolled 100 patients with confirmed metastatic CRC without RAS nor BRAF mutations in their primary tumors. Patients were treated with first-line systemic chemotherapy that included EGFR blockade. We obtained ctDNA from each patient before they started chemotherapy, and at the time they acquired resistance. We detected RAS, BRAF (V600E), and PIK3CA mutations using digital polymerase chain reaction. Results: In the ctDNA obtained before starting chemotherapy, RAS, BRAF, and PIK3CA mutations were detected in 10, 4, and 2 of the 100 patients, respectively. No patients had both RAS and BRAF mutations in their ctDNA; however, one patient had both BRAF and PIK3CA mutations. Eighty-nine patients had measurable tumor lesions. Of those, 3 experienced a complete response (CR), 72 had a partial response (PR), 12 had stable disease (SD), and 2 had progressive disease (PD). Of 14 patients who had measurable tumors and RAS or BRAF mutations in the ctDNA, 11 (79%) had a PR and 3 (21%) had SD. Of 75 patients who had measurable tumors and no RAS or BRAF mutations in the ctDNA, 3 (4%) experienced a CR, 61 (81%) had PR, 9 (12%) had SD, and 2 (3%) had PD. Patients with RAS or BRAF mutations and patients with neither mutation had response rates of 79% and 85%, respectively. There was no significant difference. Conclusions: As we previously reported, incidence of RAS and BRAF heterogeneity were 10% and 4%, respectively. Heterogeneity of RAS and BRAF mutations had no effect on the response rate of EGFR blockade as first line chemotherapy. Other possible causes of resistance could be MET or HER-2 amplification, PIK3CA mutation, or ALK fusion. The effect of heterogeneity on the duration of response is of great interest; however, one-third of patients are still undergoing treatment with EGFR blockade. Clinical trial information: 000031177 .

Objectives: To clarify the risk factors affecting prognosis after primary tumor resection (PTR) in patients with metastatic colorectal cancer with synchronous peritoneal metastasis (mCRC-SPM). Methods: Patients were enrolled prospectively in the JSCCR project "Grading of Peritoneal Seeding in Colorectal Cancer." Factors that may influence overall survival & horbar;age, sex, location of the primary tumor, lymph node metastasis, presence of liver metastasis, degree of peritoneal metastasis, peritoneal cancer index (PCI), cancer cure, and postoperative chemotherapy & horbar;in the PTR group were examined using multivariate analysis. Results: Of the 133 enrolled patients with mCRC-SPM, 112 patients underwent PTR. Among them, 26 (23.2%) had mCRC-SPM of grade P1, 47 (42.0%) of P2, and 39 (34.8%) of P3. The median PCI was 4 (range, 1-28); no surgery-related deaths occurred. Postoperative complications of Clavien-Dindo classification >= grade 2 were observed in 20 (17.9%) patients. R0 surgery became more difficult as the degree of dissemination increased, and the PTR group had a significantly better prognosis than the non-PTR group. In the multivariate analysis, age >= 75 years, rectal cancer, presence of liver metastasis, higher PCI, non-curative resection, and non-treatment with systemic chemotherapy were associated with poor prognosis in patients after PTR. Conclusions: In patients with mCRC-SPM, postoperative complications are infrequent for P1 with localized peritoneal dissemination, and PTR may be considered as aggressive treatment. Factors including age >= 75 years, rectal cancer, presence of liver metastasis, increased PCI, non-curative resection, and non- treatment with systemic chemotherapy are associated with a reduced survival benefit from PTR.

Background:Chemotherapy is the typical choice for treating colorectal cancer with synchronous peritoneal metastases. Nonetheless, surgical resection may be chosen if the metastases are resectable. Unfortunately, there is no reliable preoperative or intraoperative prognostic indicator. This study aimed to determine the prognostic significance of the preoperative Glasgow prognostic score (GPS) in colorectal cancer patients with synchronous peritoneal metastases. Methods:We conducted a prospective study on 143 patients with colorectal cancer and concurrent peritoneal metastases. Our analysis included prognostic factors, such as the GPS, using data from the institutional observational study by the Japanese Society for Cancer of the Colon and Rectum. Results:The 3-year survival rates for the GPS0 or 1 and GPS2 groups were 32.7% and 14.3%, respectively, with a significantly worse prognosis in the GPS2 group (p = 0.003). Multivariate analysis identified GPS2 (p = 0.006) and the peritoneal cancer index (PCI) (p = 0.029) or the Japanese surgical peritoneal metastasis grade (p = 0.009) as independent poor prognostic factors. Additionally, the GPS0 or 1 group with total resection of peritoneal metastases had a significantly better prognosis than the non-resection group (p < 0.001); however, there was no difference between the GPS2 group with total peritoneal resection and the non-resection group (p = 0.713). Conclusions:Preoperative GPS2 is an independent poor prognostic factor in patients with colorectal cancer and synchronous peritoneal metastases, and surgical resection does not improve prognosis in patients with GPS2. Preoperative GPSs may be used as indicators for surgical resection of synchronous peritoneal metastases.

Objectives: Mismatch repair (MMR)-deficient (dMMR) colorectal cancer (CRC) have been largely categorized into three subtypes: MLH1-methylated, Lynch syndrome (LS)-associated, and Lynch-like syndrome (LLS)-associated. No studies have examined the prevalence and subtypes of synchronously diagnosed dMMR CRCs in detail. Therefore, this study aimed to examine the frequency and molecular characteristics of the dMMR status among multiple synchronous CRCs to clarify the clinical significance of identifying patients with such tumors. Methods: Immunohistochemistry (IHC) of MMR proteins (MLH1, MSH2, MSH6, and PMS2) was performed for surgically and endoscopically resected (in conjunction with surgical resection) lesions from consecutive patients with initially diagnosed multiple synchronous CRCs between July 2014 and June 2020. When necessary, MLH1-methylation analysis and testing of germline and somatic MMR genes were performed. Results: In total, 133 patients (33 females) had 309 lesions. The combinations of synchronous tumor sites were the left-sided colon/rectum only (n=67, 50.4%), both the right-sided colon and left-sided colon/rectum (n=42, 31.6%), and the right-sided colon only (n=24, 18.0%). IHC showed a loss of expression of at least one MMR protein in 10 (7.5%) of 133 patients and 17 (5.5%) of 309 lesions. Molecular analysis revealed that these 10 patients were categorized as having MLH1-methylated (n=5, 3.8% of all patients), LS-associated (n=4, 3.0%), or LLS-associated (n=1, 0.8%) CRC. Conclusions: Our data will be useful for genetic counseling in patients with synchronous CRCs suspected of having LS. Screening for LS using IHC for MMR proteins in individuals with multiple synchronous CRCs is an effective approach.

An 81-year-old woman visited our hospital for severe anemia and was diagnosed with ascending colon cancer with a tumor thrombus in the superior mesenteric vein(SMV). After 8 courses of mFOLFOX6+bevacizumab therapy followed by 7 courses of fluorouracil and leucovorin+bevacizumab therapy, the primary lesion and tumor thrombus were found to be shrinkage. Then we performed robot-assisted right hemicolectomy and resection of SMV involving the tumor thrombus. The patient was discharged on postoperative day 19. Histological findings revealed residual tumor thrombus in the SMV. The patient is currently under observation at 4 months postoperatively without adjuvant chemotherapy.

Lynch syndrome (LS) is a genetic condition characterized by an increased risk of colorectal cancer and other associated malignancies. With the limited information available regarding extracolonic tumours, this study aimed to explore tumours associated with LS in the Japanese population and discuss the potential differences in causative pathogenic genetic variants and their phenotypic expression compared with Western cohorts. This multicentre retrospective cohort study analysed 316 genetically confirmed LS cases (148 men and 168 women) from 13 institutions. We analysed the incidence of extracolonic LS-associated tumours according to sex and gene variants, including MLH1 (124 cases), MSH2 (139), MSH6 (37), PMS2 (11), and EPCAM (5). Extracolonic tumour types assessed included 88 endometrial, 47 gastric, 27 small intestinal, 21 urothelial, 13 ovarian, 8 biliary tract, 5 brain, three pancreatic, and 18 other cancers. The cumulative risk by age 70 was 66% for endometrial cancer, 23% for gastric cancer, 14% for small intestine cancer, 10% for upper urothelial cancer, 9% for ovarian cancer, and 3% for biliary tract cancer. The mean age at diagnosis varied, with gastric and small intestinal cancers presenting later in life than urothelial, endometrial, and ovarian cancers. Men had a higher risk of most cancers, except for gynaecological cancers. Gastric and urothelial cancers were primarily associated with MLH1 and MSH2 pathogenic variants. This study highlights the need for tailored surveillance programmes based on cancer type, sex, causative pathogenic genetic variants, and risk profiles to effectively manage LS in Japan.

Peutz–Jeghers syndrome (PJS), a rare genetic disorder characterized by hamartomatous gastrointestinal polyps, poses increased risks of various cancers. Despite the importance of early intervention, the optimal timing for jejunal-ileal polypectomy remains unclear owing to the limited number of comparative studies. Herein, we conducted a nationwide survey in Japan and analyzed data from 184 patients with PJS identified through a two-stage sampling process. The initial screening of 2912 medical institutions yielded 1748 facilities, of which 1077 responded to the survey. Time-dependent Cox proportional hazards models and logistic regression analyses were used to examine the association between the timing of jejunal-ileal polypectomy and the risk of surgery for intussusception. Among 184 patients (47.0