Pseudomyxoma Peritonei Research Articles

Comparison of functional characterization of cancer stem cells in different tumor tissues of pseudomyxoma peritonei.

Pseudomyxoma peritonei (PMP) is a rare malignant peritoneal tumor that readily recurs and metastasizes. Studies have shown that cancer stem cells (CSCs) play an important role in tumor recurrence, metastasis, and prognosis. In this study, our aim was to isolate CSCs from various tissues of PMP patients and compare their proliferation, migration, and anti-inflammatory abilities. We identified CSCs subsets with markers CD133+, CD166+, and CD133+/CD166+ at the gene level using single-cell mRNA sequencing (scRNA-seq). Appendiceal CSCs (AC), peritoneal CSCs (PC), and mucous CSCs (MC) were obtained using MACSQuant Tyto sorting technology and FlowSight imaging flow cytometry. The cells were cultured and markers were identified. Finally, the functional phenotypes of the three cell types were compared. CSCs content was highest in the appendiceal tumor tissue and lowest in the mucous tissue. The cell viability rate of the sorted CSCs was above 98%, and the positive rate of CD133+ and CD166+ was 70-80%, and CD133+/CD166+ was about 30%. Among the three types of CSCs, MC had the highest proliferation ability, and TNF-α has the greatest inhibitory effect on AC migration. AC in patients was more inert and anti-inflammatory, whereas abdominal cavity MC and PC were more active. This study revealed the biological characteristics of CSCs in different tumor tissues of patients with PMP, providing a reference for future targeted CSCs therapy.

Natural History from Appendiceal Mucocele to Jelly Belly

Mucocele of the appendix and pseudomyxoma peritonei are rare diseases. The clinical findings are nonspecific in the early stages of the disease. The sequelae of appendiceal mucocele, its perforation, and extensive peritoneal involvement via pseudomyxoma peritonei (jelly belly) are repeatedly described in the literature. We present the typical findings in the natural history of the disease.

Imaging of Peritoneal Surface Malignancies.

Management of peritoneal surface malignancies is currently entrusted to a multimodality approach. Computed tomography (CT) scan remains the first imaging method despite the limitations in identifying small implants in critical regions. Magnetic resonance imaging is usually recommended for its performance in small implants, mesentery, and small bowel assessment. Positron emission tomography/CT plays an important role only in pseudomyxoma peritonei. Thus, becoming aware of the imaging strengths and drawbacks and having a multimodality imaging approach might be the best option for the patients.

Intraoperative hyperthermia is associated with increased acute kidney injury following cytoreductive surgery and hyperthermic intraperitoneal chemotherapy: a retrospective cohort study

Background Acute kidney injury (AKI) is common after cytoreduction surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) for peritoneal surface malignancies. Herein we analyzed the association between intraoperative hyperthermia and AKI following CRS-HIPEC. Methods In this retrospective cohort study, we collected baseline and perioperative data from patients who underwent CRS-HIPEC mainly for pseudomyxoma peritonei between 2014 and 2020. Nasopharyngeal temperature was recorded at 5-min intervals. The area above the threshold was calculated for intraoperative hyperthermia (>37.0 °C). AKI was diagnosed and classified according to the KDIGO creatinine criteria. A multivariable logistic regression model was established to assess the association between hyperthermia and AKI. Results A total of 480 patients were included in the analysis. Of these, 10.6% (51/480) developed AKI within 7 postoperative days. After correction for confounding factors, a larger area above the threshold of hyperthermia was significantly associated with an increased risk of AKI (odds ratio [OR] 1.36, 95% CI 1.14–1.63, p = 0.001). Among other factors, older age (OR 1.05, 95% CI 1.02–1.09, p = 0.002), postoperative hypotension requiring vasopressors (OR 2.09, 95% CI 1.02–4.27, p = 0.042), and intraperitoneal chemotherapy containing cisplatin (OR 2.75, 95% CI 1.20–6.33, p = 0.017) were also associated with an increased risk of AKI. Patients with AKI required longer mechanical ventilation, stayed longer in the intensive care unit and hospital, developed more complications, and required more intensive care unit readmission. Conclusions Among patients undergoing CRS-HIPEC, intraoperative hyperthermia was independently associated with a higher risk of AKI; this effect was additive to other risk factors including cisplatin-containing chemotherapy.

Status of and Challenges in Therapy of Mucinous Ovarian Cancer Associated with Pseudomyxoma Peritonei Syndrome: Review of Current Options and Future Treatment Trends

Objective: Pseudomyxoma peritonei (PP) is a rare condition, and differentiating between primary and secondary ovarian causes is crucial for determining the appropriate oncological therapy. Given the resistance of ovarian mucinous carcinoma to standard platinum-based chemotherapy, the objective of this review is to present the current therapeutic approaches and summarize the emerging trends in the treatment of this disease. Methods: The authors conducted an exhaustive evaluation of studies published over a 14-year period (June 2010–May 2024) concerning pseudomyxoma peritonei, mucinous ovarian carcinoma, ovarian causes of PP, and ovarian cancer using the following databases: PubMed, Scopus, and Science Direct. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. The results were organized into seven subchapters and analyzed. Results: The analyzed studies present surgery followed by HIPEC as the current therapy with the best long-term survival results. However, the oncological treatment is unsatisfactory, and the choice of therapy depending on the primary origin of the tumor becomes particularly important. For the differential diagnosis between pseudomyxoma due to a gastrointestinal cause and that of ovarian origin, genetic analyses are recommended; these include the characteristics of the mucin present in the lesion, as the therapeutic response can have contradictory results depending on the primary origin of the tumor. Conclusions: Surgery followed by HIPEC remains the standard for resectable cases. However, oncological treatment has controversial results in the case of mucinous ovarian carcinoma compared to other types of ovarian cancer and to metastatic ovarian tumors associated with pseudomyxoma of the peritoneum. Based on the articles included in this review, it was found that the current trend is the study of mucin as a resistance factor against chemotherapy based on platinum products and the targeting of oncological therapy according to the tumor’s genetic characteristics.

Pseudomyxoma Peritonei Lesion of the Thoracic Spine: A Case Report and Literature Review

Background: Pseudomyxoma peritonei (PMP) is a rare condition, with no previously described location in the spine. Here is presented a case of PMP extension to the thorax and then the spine, treated with two-level vertebrectomy, laminectomy, and posterior fusion. Case Report: We report here the case of a 64-year-old man presenting pathological fractures of T6 and T7 due to PMP extension to the pleural cavity and thoracic spine. He presented interscapular pain with mild spinal cord compression symptoms. He was treated by achieving T5-T8 laminectomy, T2-T10 pedicle fixation, and T6-T7 vertebrectomy. The postoperative course was uneventful apart from a pulmonary embolism (PE) with favorable evolution under anticoagulants. Conclusion: To achieve spinal cord decompression, kyphosis correction, and spine stabilization, a two-level vertebrectomy, laminectomy, and posterior fusion would be beneficial for a PMP lesion of the thoracic spine.

Bilateral erector spinae plane block by multiple injection for pain control in pseudomyxoma peritonei surgery: a single-blind randomized controlled trial

ObjectiveCurrently, the primary surgical treatment for pseudomyxoma peritonei (PMP) is cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC). The perioperative period is frequently accompanied by severe pain. Erector spinae plane block (ESPB) can enhance analgesia for abdominal surgery. The purpose of this study was to compare the analgesic effects of bilateral multiple-injection ESPB in patients with PMP.MethodsFifty patients with PMP were randomly divided into two groups: the ESPB combined with general anesthesia group (Group E) and the general anesthesia alone group (Group C). Prior to the induction, patients in Group E underwent ESPB at the T7 and T11 levels. The primary outcome was the visual analog scale (VAS) scores during rest at 6 h post-extubation. Secondary outcomes included intraoperative and postoperative opioid consumption, time for first rescue analgesia, frequency distribution of rescue analgesia, incidence of nausea and vomiting, adverse events associated with ESPB.ResultsThe Visual Analogue Scale (VAS) scores in Group E were significantly lower compared to Group C at immediate post-extubation (1.6 ± 0.9 vs. 2.4 ± 1.2, P = 0.008), and at 2 (1.9 ± 1.2 vs. 3.2 ± 1.1, P < 0.001), 4 (2.4 ± 1.5 vs. 3.7 ± 1.0, P = 0.001), and 6 h (2.7 ± 1.1 vs. 3.8 ± 1.4, P = 0.004) post-extubation during rest. Similarly, the VAS scores in Group E were significantly lower than those in Group C at immediate post-extubation (3.0 ± 1.4 vs. 4.6 ± 1.2, P < 0.001), and at 2 (3.8 ± 1.7 vs. 4.9 ± 1.4, P = 0.019), 4 (3.5 ± 1.3 vs. 5.3 ± 1.5, P < 0.001), and 6 h (3.9 ± 1.8 vs. 4.9 ± 1.3, P = 0.004) post-extubation during movement. In Group E, the intraoperative remifentanil administration (2319.3 ± 1089.5 vs. 2984.6 ± 796.1, P = 0.017) and the amount of rescue analgesia within 2 h post-extubation (0 vs. 4, P = 0.037) were significantly less than in Group C, and the first rescue analgesia time was shorter as well (231.4 ± 147.5 vs. 668.8 ± 416.7, P < 0.001).ConclusionCompared to general anesthesia alone, bilateral multiple-injection ESPB with 0.2% ropivacaine can enhance analgesia and reduce opioid administration in patients with PMP. However, the duration of analgesia with ESPB is relatively short due to the low concentration of the local anesthetic used.Trial registrationChinese Clinical Trial Registry, ChiCTR2300069504, 20/03/2023.

A combinatorial culture strategy to develop pseudomyxoma peritonei organoid models.

Few preclinical models of pseudomyxoma peritonei (PMP) have been developed, probably due to the tumor's low incidence and its peculiar characteristics of slow growth. Therefore, there is a need to develop more refined PMP models that better reflect its characteristics. The aim of the study is to develop a culture strategy to generate organoid models derived from PMP patient samples. We followed a strategy based on combinatorial culture conditions that include the different factors essential for PMP growth and that mimic the microenvironment present in the patients. We cultured PMP samples in the presence of the various factors produced by the niche environment of PMP. We obtained 12 PMP organoid models, each of which grows under specific culture conditions. PMP-derived organoids show long-term expansion capacity and reproduce the genetic landscape and histological phenotype of the tumor of origin. The organoids we developed faithfully reproduce the key features of PMP disease and will allow us to understand the biology of PMP. With them, we will be able to identify key regulatory networks that support PMP progression, providing a platform for multilevel preclinical testing, identify novel diagnostic biomarkers, and generate novel targets for patient treatments.

Molecular Profiling of Low-Grade Appendiceal Mucinous Neoplasms (LAMN).

Low-grade appendiceal mucinous neoplasia (LAMN) represents a relatively rare tumor of the appendix typically diagnosed incidentally through appendectomy for acute appendicitis. In cases where perforation occurs, mucinous content may disseminate into the abdominal cavity, leading to the development of pseudomyxoma peritonei (PMP). The primary objective of this study was to elucidate the molecular characteristics associated with various stages of LAMN and PMP. DNA was extracted from LAMN, primary PMPs, recurrent PMPs, and adenocarcinomas originating from LAMN. The subsequent analysis involved the examination of mutational hotspot regions within 50 cancer-related genes, covering over 2800 COSMIC mutations, utilizing amplicon-based next-generation sequencing (NGS). Our findings revealed activating somatic mutations within the MAPK-signaling pathway across all tumors examined. Specifically, 98.1% of cases showed mutations in KRAS, while one tumor harbored a BRAF mutation. Additionally, GNAS mutations were identified in 55.8% of tumors, with no significant difference observed between LAMN and PMP. While LAMN rarely displayed additional mutations, 42% of primary PMPs and 60% of recurrent PMPs showed additional mutations. Notably, both adenocarcinomas originating from LAMN showed mutations within TP53. Furthermore, 7.7% (4/52) of cases exhibited a potentially targetable KRAS G12C mutation. In four patients, NGS analysis was performed on both primary PMP and recurrent PMP/adenocarcinoma samples. While mutations in KRAS and GNAS were detected in almost all samples, 50% of recurrent cases displayed an additional SMAD4 mutation, suggesting a notable alteration during disease progression. Our findings indicate two key points: First, mutations within the MAPK pathway, particularly in KRAS, are evident across all tumors, along with a high frequency of GNAS mutations. Second, progression toward PMP or adenocarcinoma is associated with an accumulation of additional mutations within common oncogenic pathways.

Targeted Genetic Sequencing Analysis of 223 Cases of Pseudomyxoma Peritonei Treated by Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy Shows Survival Related to GNAS and KRAS Status.

Pseudomyxoma peritonei (PMP) is an unusual condition with unique behaviour caused by a mucinous neoplasm, usually arising from the appendix. The aim of this study was to evaluate the prevalence of genomic alterations in clinical specimens of PMP using a targeted assay and correlate the findings with clinical, pathological and outcome data. Sequencing data from 223 patients were analysed. The median follow-up interval was 48 months. The primary neoplasm was appendiceal in 216 patients, ovarian in 4, urachal in 2 and renal in one. We confirmed common mutations in GNAS and KRAS (42% each) with significant co-occurrence of variants in these genes. TP53 mutations were found in 8%. Other mutations were rare but included novel mutations in BAP1 and ERBB4. Of 17 patients with acellular peritoneal mucin, 6 (35%) were positive for DNA mutations. The non-appendiceal cases generally showed a similar mutational landscape to the appendiceal lesions with GNAS and KRAS commonly mutated, although one urachal lesion showed multi-hit TP53 mutation without variants in either GNAS or KRAS. Survival was significantly associated with the grade of the primary neoplasm, the grade of the peritoneal disease, the completeness of cytoreduction score and with mutation in either GNAS, KRAS or both. The hazard ratio (HR) associated with mutation in GNAS and/or KRAS was 1.87 (p = 0.004). Survival outcome was more closely associated with the grade of the peritoneal disease than with the grade of the primary neoplasm. Our findings support the developing concept that mutational analysis may provide prognostic information in patients with PMP.

Association between preoperative appendiceal histology grade and Pseudomyxoma peritonei grade offer a solution to avoid right hemicolectomy during cytoreductive surgery and HIPEC

Introduction& objectives: Treatment of PMP consists of appendectomy, cytoreductive surgery (CRS) and HIPEC. Right-sided hemicolectomy is necessary only when PMP is high grade, given the lymphatic invasion risk. To date, no single preoperative factor was identified as predictive of PMP grade.Materials & methods: Preoperative factors of a prospective cohort study on PMP were retrospectively analysed, in order to identify situations linked with high or low grade appendiceal PMP. The main outcome was PMP grade on definitive histology after CRS. Resultsn=105. In univariate analysis, the grade of the appendiceal tumor, systematically reviewed in an expert center, showed an OR of 25.00 (95% CI: 3.30–189.27; p = 0.001) and an NPV of 93.75 [85.36, 100]. Peritoneal biopsy demonstrated an OR of 19.80 (95% CI: 2.30–170.71; p = 0.002) and a PPV of 90 [71.41, 100]. In multivariate analysis, these two factors remained significantly associated with PMP grade. ConclusionWhenever appendiceal tumor is low grade on preoperative histology, the colon has to be spared unless completeness of CRS is compromised, which is a high-grade feature in fact. In case of high grade appendiceal tumor and/or peritoneal biopsy, right-sided hemicolectomy is warranted. If no histology is available preoperatively, adapt to intraoperative lesions as no preoperative factors seem to be predictive.

Oncological outcomes and risk factors for recurrence of mucinous borderline ovarian tumors: A 15-year experience at a tertiary center.

The most common subtype of borderline ovarian tumors in Asia is mucinous borderline ovarian tumors (mBOTs). Intraoperative distinction from mucinous carcinoma can be difficult. Despite the indolent behavior of mBOTs, recurrence or metastases may occur. The objectives of this study were to determine the oncological outcomes of mBOTs and the risk factors for their recurrence. This retrospective study enrolled patients with mBOTs treated or referred to our institution between January 2005 and December 2019. Histological reviews of the recurrent cases (primary and recurrent or metastatic tumors) were performed. Patients with other tumor subtypes, pseudomyxoma peritonei, or no in-house operation were excluded. Two hundred thirty-two patients were diagnosed with mBOTs. The median follow-up was 52 months. Six patients (2.58%) had tumor recurrence or metastasis. The risk factors for recurrence were a ruptured tumor, residual tumor after an operation, high serum CA19-9 level, and stage of the disease. The recurrence rates of fertility-sparing and radical surgery were not significantly different. Detailed surgical staging, intraepithelial carcinoma, and microinvasion were also not associated with disease recurrence. mBOTs have an excellent prognosis. Currently, fertility-sparing surgery is the standard treatment, showing no significant difference in oncological outcomes compared to radical surgery. Patients with risk factors should be closely monitored.

Risk stratification of surveillance for low-grade appendiceal mucinous neoplasms

BackgroundLow-grade appendiceal mucinous neoplasms (LAMNs) can progress to pseudomyxoma peritonei (PMP). The incidence and risk factors for recurrence are unclear, and there is a lack of consensus on the need and duration of surveillance imaging. MethodsPatients at the Mayo Clinic in Rochester, Minnesota, with a histologic diagnosis of LAMNs confined to the appendix and limited involvement of the right lower quadrant from 1992 to 2023 were included. Associations between recurrence and risk factors were assessed using Kaplan-Meier curves and Cox proportional hazards regression. ResultsA total of 125 patients with LAMNs underwent abdominal imaging surveillance for a median of 51.2 months (IQR, 26–92). Of note, 5 patients (4%) recurred, all of which were PMP. Overall, the 5- and 10-year cumulative recurrence incidence rates were 3% and 6%, respectively. The median time to recurrence was 24 months (IQR, 23–87). Only LAMNs limited to the right lower quadrant and LAMN tumor size of <2 cm were associated with recurrence (P < .05). The 5- and 10-year cumulative recurrence risks were 12% and 30%, respectively, for the 21 patients with either risk factor. Only 1% of patients without these 2 risk factors developed a recurrence at 10 years. ConclusionThe overall recurrence risk of LAMN after resection is low. Appendectomy is sufficient for LAMN. Select patients with acellular mucin confined to the right lower quadrant and a tumor size of <2 cm are at higher risk of recurrence. Thus, long-term surveillance is recommended for high-risk individuals. Conversely, LAMNs without risk factors can be safely observed expectantly.

Decision Regret in Patients with Appendiceal Cancer Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy.

Decision regret is an emerging patient reported outcome. The aim of this study was to assess the incidence of regret in patients with appendiceal cancer (AC) who underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). An anonymous survey was distributed to patients through the Appendix Cancer and Pseudomyxoma Peritonei (ACPMP) Research Foundation. The Decision Regret Scale (DRS) was employed, with DRS > 25 signifying regret. Patient demographics, tumor characteristics, postoperative outcomes, symptoms (FACT-C), and PROMIS-29 quality of life (QoL) scores were compared between patients who regretted or did not regret (NO-REG) the procedure. A total of 122 patients were analyzed. The vast majority had no regret about undergoing CRS-HIPEC (85.2%); 18 patients expressed regret (14.8%). Patients with higher regret had: income ≤ $74,062 (72.2% vs 44.2% NO-REG; p = 0.028), major complications within 30 days of surgery (55.6% vs 15.4% NO-REG; p < 0.001), > 30 days hospital stay (38.9% vs 4.8% NO-REG; p < 0.001), a new ostomy (27.8% vs 7.7% NO-REG; p = 0.03), >1 CRS-HIPEC procedure (56.3% vs 12.6% NO-REG; p < 0.001). Patients with worse FACT-C scores had more regret (p < 0.001). PROMIS-29 QOL scores were universally worse in patients with regret. Multivariable analysis demonstrated > 30 days in the hospital, new ostomy and worse gastrointestinal symptom scores were significantly associated with regret. The majority of patients with AC undergoing CRS-HIPEC do not regret undergoing the procedure. Lower income, postoperative complications, an ostomy, undergoing > 1 procedure, and with worse long-term gastrointestinal symptoms were associated with increased regret. Targeted perioperative psychological support and symptom management may assist to ameliorate regret.

Stemness and hybrid epithelial-mesenchymal profiles guide peritoneal dissemination of malignant mesothelioma and pseudomyxoma peritonei.

Intrabdominal dissemination of malignant mesothelioma (MM) and pseudomyxoma peritonei (PMP) is poorly characterized with respect to the stemness window which malignant cells activate during their reshaping on the epithelial-mesenchymal (E/M) axis. To gain insights into stemness properties and their prognostic significance in these rarer forms of peritoneal metastases (PM), primary tumor cultures from 55 patients selected for cytoreductive surgery with hyperthermic intraperitoneal chemotherapy were analyzed for cancer stem cells (CSC) by aldehyde dehydrogenase 1 (ALDH1) and spheroid formation assays, and for expression of a set of plasticity-related genes to measure E/M transition (EMT) score. Intratumor heterogeneity was also analyzed. Samples from PM of colorectal cancer were included for comparison. Molecular data were confirmed using principal component and cluster analyses. Associations with survival were evaluated using Kaplan-Meier and Cox regression models. The activity of acetylsalicylic acid (ASA), a stemness modifier, was tested in five cultures. Significantly increased amounts of ALDH1bright-cells identified high-grade PMP, and discriminated solid masses from ascitic/mucin-embedded tumor cells in both forms of PM. Epithelial/early hybrid EMT scores and an early hybrid expression pattern correlated with pluripotency factors were significantly associated with early peritoneal progression (p = .0343 and p = .0339, respectively, log-rank test) in multivariable models. ASA impaired spheroid formation and increased cisplatin sensitivity in all five cultures. These data suggest that CSC subpopulations and hybrid E/M states may guide peritoneal spread of MM and PMP. Stemness could be exploited as targetable vulnerability to increase chemosensitivity and improve patient outcomes. Additional research is needed to confirm these preliminary data.

An observational cohort of patients with colorectal peritoneal metastases or pseudomyxoma peritonei treated with CRS-HIPEC: Development and first results of the Dutch CRS-HIPEC quality registry

IntroductionTo improve care for patients with colorectal peritoneal metastases (CRC-PM) or pseudomyxoma peritonei (PMP), the Dutch CRS-HIPEC quality registry was initiated in 2019. The aims are to describe the development and content of this registry and to give insight into the data collected during the first years. Materials and methodsThe registry is an observational cohort in the Netherlands. All patients with CRC-PM or PMP who intend to undergo cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) from 6 hospitals are included. Clinical data and outcomes (including hospital variation) were analyzed. ResultsIn 2019–2022, 889 patients were included in the CRS-HIPEC quality registry: 749 (84 %) with CRC-PM and 140 (16 %) with PMP. Peritoneal metastases were diagnosed synchronously in 51 % of CRC-PM patients and in 94 % of PMP patients. In patients undergoing complete CRS, the median peritoneal cancer index was 8 (IQR 4–13) for CRC-PM and 15 (IQR 6–26) for PMP. Complete cytoreduction was achieved in 639 CRC-PM patients (97 %) and 108 PMP patients (82 %). HIPEC was mainly performed with mitomycin C (CRC-PM: 94 %, PMP: 92 %). Major postoperative complications (Clavien-Dindo grade ≥3) occurred in 148 CRC-PM patients (22 %) and 30 PMP patients (23 %) with 90-day mortality rates of 2 %. In CRC-PM, differences between hospitals were observed regarding proportions of diagnostic laparoscopies/laparotomies, (neo)adjuvant treatment, ostomy formations and re-admissions. ConclusionThe CRS-HIPEC quality registry provides insight into the outcomes of CRS-HIPEC and enables clinical auditing and observational cohort studies aiming to improve treatment outcomes for patients with CRC-PM and PMP.

The risk of developing pseudomyxoma peritonei from a non-perforated low grade appendiceal mucinous neoplasm found at appendicectomy

IntroductionLow-grade appendiceal mucinous neoplasms (LAMNs) are classified as non-perforated (pTis, pT3) or perforated (pT4), and considered precursors of pseudomyxoma peritonei (PMP). This study aims to quantify the risk of developing PMP from pTis and pT3 LAMNs. Materials and methodsRetrospective analysis of a prospectively collected database identified LAMN patients referred to a specialist centre from 2004 to 2019. pT4 LAMNs and other appendix tumours were excluded. All patients had specialist review of their pathology, operation note, and a CT scan (at least 6 weeks post-operatively). Surveillance CTs were then performed at 6, 12, 24, 36, 48, & 60 months, with tumour markers (CEA, CA19-9, CA125). Results193 pT3/pTis LAMN patients were included (pTis = 153, pT3 = 40). Median follow-up = 6.45 (3.91–22.13) years, M:F ratio = 1:1.57, and median age = 57 (23–83) years. Initial surgery included: appendicectomy (67 %), appendicectomy + visceral resection (6 %), and right hemicolectomy (27 %). R1 resections were identified in 5/193 patients (2.5 %). 3 R1 patients underwent re-operation (2 caecal pole excision and 1 ileocecectomy), none of which had residual tumour. 8/193 patients (4 %) were lost to follow up. None of the remaining 185 developed PMP. ConclusionThis is the largest reported series of pTis/pT3 LAMNs with standardised follow-up in the literature. LAMNs correctly classified as pT3/pTis (after careful specialist review of pathology, operation note, and a baseline post-operative CT) have negligible risk of developing PMP and should have low intensity surveillance. If completely excised, further surgery is not indicated. R1 resections should be considered on an individual basis at a specialist centre.

Selective Gastrectomy with Knowledge of Gastric Anatomy and Blood Supply are Key to Complete Tumour Removal in Advanced Pseudomyxoma: Single-Centre Experience with 120 Gastrectomies Over 20 Years.

The role of gastrectomy to achieve complete cytoreduction (CCR) for pseudomyxoma peritonei (PMP) is controversial due to uncertain risk/benefit ratio. The outcomes of patients who gastrectomy over a twenty-year period in a high-volume unit are reported. All patients requiring gastrectomy to achieve CCR for appendiceal PMP between 2000 and 2020 were reviewed. Demographics, disease, operative, complication, and survival data were analysed. The first and second decades were compared. A total of 2148 patients underwent CRS and HIPEC, of which 78% had CCR. Gastrectomy was performed in 7.1%. Median age was 55 years, and 52% were female. Among gastrectomy patients, 94.2% had ≥1 elevated tumour marker, and 18% had high-grade disease. Median PCI was 30, and 30% required subtotal colectomy. Clavien-Dindo III-IV complications occurred in 32%, and 90-day mortality was 1.75%. Median survival was 104 months, and 10-year OS was 47%. Comparing the two decades, total CRS cases almost tripled, with a greater proportion achieving CCR (82.2% vs. 67.8%) but fewer requiring gastrectomy (5.3% vs. 13.5%). In those who had gastrectomy, disease was more advanced (higher PCI, more high-grade disease, more colectomies) in the later period. However, on multivariable analysis, there was no difference in survival between decades. High-grade histology was the only predictor of survival. Gastrectomy can achieve good long-term survival with low mortality and acceptable morbidity and should not deter surgeons from achieving CCR. However, increasing experience shows CCR can be achieved, preserving the stomach in the majority of cases through careful consideration of the anatomy and gastric blood supply.

Progress on immuno-microenvironment and immune-related therapies in patients with pseudomyxoma peritonei.

Pseudomyxoma peritonei (PMP) is an indolent malignant syndrome. The standard treatment for PMP is cytoreductive surgery combined with intraperitoneal hyperthermic chemotherapy (CRS + HIPEC). However, the high recurrence rate and latent clinical symptoms and signs are major obstacles to further improving clinical outcomes. Moreover, patients in advanced stages receive little benefit from CRS + HIPEC due to widespread intraperitoneal metastases. Another challenge in PMP treatment involves the progressive sclerosis of PMP cell-secreted mucus, which is often increased due to activating mutations in the gene coding for guanine nucleotide-binding protein alpha subunit (GNAS). Consequently, the development of other PMP therapies is urgently needed. Several immune-related therapies have shown promise, including the use of bacterium-derived non-specific immunogenic agents, radio-immunotherapeutic agents, and tumor cell-derived neoantigens, but a well-recognized immunotherapy has not been established. In this review the roles of GNAS mutations in the promotion of mucin secretion and disease development are discussed. In addition, the immunologic features of the PMP microenvironment and immune-associated treatments are discussed to summarize the current understanding of key features of the disease and to facilitate the development of immunotherapies.

Precision Oncology and Systemic Targeted Therapy in Pseudomyxoma Peritonei.

Pseudomyxoma peritonei (PMP) is a rare and poorly understood malignant condition characterized by the accumulation of intra-abdominal mucin produced from peritoneal metastases. Currently, cytoreductive surgery remains the mainstay of treatment but disease recurrence and death after relapse frequently occur in patients with PMP. New therapeutic strategies are therefore urgently needed for these patients. A total of 120 PMP samples from 50 patients were processed to generate a collection of 50 patient-derived organoid (PDO) and xenograft (PDX) models. Whole exome sequencing, immunohistochemistry analyses, and in vitro and in vivo drug efficacy studies were performed. In this study, we have generated a collection of PMP preclinical models and identified druggable targets, including BRAFV600E, KRASG12C, and KRASG12D, that could also be detected in intra-abdominal mucin biopsies of patients with PMP using droplet digital PCR. Preclinical models preserved the histopathological markers from the original patient sample. The BRAFV600E inhibitor encorafenib reduced cell viability of BRAFV600E PMP-PDO models. Proof-of-concept in vivo experiments showed that a systemic treatment with encorafenib significantly reduced tumor growth and prolonged survival in subcutaneous and orthotopic BRAFV600E-PMP-PDX mouse models. Our study demonstrates for the first time that systemic targeted therapies can effectively control PMP tumors. BRAF signaling pathway inhibition represents a new therapeutic opportunity for patients with BRAFV600E PMP who have a poor prognosis. Importantly, our present data and collection of preclinical models pave the way for evaluating the efficacy of other systemic targeted therapies toward extending the promise of precision oncology to patients with PMP.