2022 Peritoneal Surface Oncology Group International Consensus on HIPEC Regimens for Peritoneal Malignancies: Colorectal Cancer.

BACKGROUND: Selected patients with peritoneal metastases of colorectal cancer (PM-CRC) can benefit from potentially curative cytoreductive surgery (CRS) ± hyperthermic intraperitoneal chemotherapy (HIPEC), with a median overall survival (OS) of more than 40 months. OBJECTIVE: The aims of this evidence-based consensus were to define the indications for HIPEC, to select the preferred HIPEC regimens, and to define research priorities regarding the use of HIPEC for PM-CRC. METHODS: The consensus steering committee elaborated and formulated pertinent clinical questions according to the PICO (patient, intervention, comparator, outcome) method and assessed the evidence according to the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) framework. Standardized evidence tables were presented to an international expert panel to reach a consensus (4-point, weak and strong positive/negative) on HIPEC regimens and research priorities through a two-round Delphi process. The consensus was defined as ≥ 50% agreement for the 4-point consensus grading or ≥ 70% for either of the two combinations. RESULTS: Evidence was weak or very weak for 9/10 clinical questions. In total, 70/90 eligible panelists replied to both Delphi rounds (78%), with a consensus for 10/10 questions on HIPEC regimens. There was strong negative consensus concerning the short duration, high-dose oxaliplatin (OX) protocol (55.7%), and a weak positive vote (53.8-64.3%) in favor of mitomycin-C (MMC)-based HIPEC (preferred choice: Dutch protocol: 35 mg/m2, 90 min, three fractions), both for primary cytoreduction and recurrence. Determining the role of HIPEC after CRS was considered the most important research question, regarded as essential by 85.7% of the panelists. Furthermore, over 90% of experts suggest performing HIPEC after primary and secondary CRS for recurrence > 1 year after the index surgery. CONCLUSIONS: Based on the available evidence, despite the negative results of PRODIGE 7, HIPEC could be conditionally recommended to patients with PM-CRC after CRS. While more preclinical and clinical data are eagerly awaited to harmonize the procedure further, the MMC-based Dutch protocol remains the preferred regimen after primary and secondary CRS.

The 2022 PSOGI International Consensus on HIPEC Regimens for Peritoneal Malignancies: HIPEC Technologies.

This manuscript reports the results of an international consensus on technologies of hyperthermic intraperitoneal perioperative chemotherapy (HIPEC) performed with the following goals: To provide recommendations for the technological parameters to perform HIPEC. To identify the role of heat and its application forms in treating peritoneal metastases. To provide recommendations regarding the correct dosimetry of intraperitoneal chemotherapy drugs and their carrier solutions. To identify for each intraperitoneal chemotherapy regimen the best dosimetry and fractionation. To identify areas of future research pertaining to HIPEC technology and regimens. This consensus was performed by the Delphi technique and comprised two rounds of voting. In total, 96 of 102 eligible panelists replied to both Delphi rounds (94.1%) with a consensus of 39/51 questions on HIPEC technical aspects. Among the recommendations that met with the strongest consensus were those concerning the dose of HIPEC drug established in mg/m2, a target temperature of at least 42°C, and the use of at least three temperature probes to pursue hyperthermia. Ninety minutes as the ideal HIPEC duration seemed to make consensus. These results should be considered when designing new clinical trials in patients with peritoneal surface malignancies.

PIPAC Pharmacologic and Clinical Data.

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) emerged as an innovative intraperitoneal chemotherapy delivery system to overcome the issue of limited efficacy of systemic therapies to induce response in peritoneal malignancies. Promising results for patients with mesothelioma peritonei and peritoneal metastasis from gastric, ovarian, colorectal, pancreatic, and hepatobiliary tumors origin are changing the landscape for patients otherwise just facing palliative treatment. Ongoing trials will shed more light on the actual benefits of PIPAC.

Review of 2022 PSOGI/RENAPE Consensus on HIPEC.

The 2022 PSOGI (Peritoneal Surface Oncology Group International) and RENAPE (French Network for Rare Peritoneal Malignancies) consensus on hyperthermic intraperitoneal chemotherapy (HIPEC) was a comprehensive effort aimed at standardizing treatment protocols for various peritoneal malignancies. This initiative is critical due to the wide range of technical variations in HIPEC procedures and the resulting need for standardization to ensure consistent and effective patient care and meaningful audit of multicenter data.

The 2022 PSOGI International Consensus on HIPEC Regimens for Peritoneal Malignancies: Methodology.

BACKGROUND: A group of experts from the Peritoneal Surface Oncology Group International (PSOGI) and the BIG-RENAPE group carried out a consensus among surgeons experienced in treating peritoneal malignancies from around the world to derive recommendations on indications of hyperthermic intraperitoneal chemotherapy (HIPEC), choice and details of HIPEC regimens, and areas for future research. This manuscript describes the methodology of achieving this consensus and the degree of participation of experts. METHODS: The Delphi technique was used and the questionnaire comprised three categories: evidence-based recommendations using the GRADE (Grades of Recommendation, Assessment, Development, and Evaluation) system with the PICO (patient, intervention, comparison, and outcome) method, an opinion survey, and research recommendations. A consensus was achieved if any one option had >50% of votes, or positive or negative recommendations combined had > 70% of votes. RESULTS: Of the 145 experts solicited, 71.1% in round I and 72.2% in round II took the survey. Participation was highest among surgeons treating both gastrointestinal and gynecological malignancies. Of 113 questions, after round I, a consensus was achieved for 72 (63.7%) questions, and after the second round, consensus was achieved for another 22 (19.4%) questions, making a total of 94 (83.1%) questions for which a consensus was achieved. CONCLUSION: This consensus was carried out using a thorough review of literature and robust rating of evidence, and included key experts and opinion leaders from across the world. The results could guide clinicians on the use of HIPEC, both in their day-to-day clinical practice and in designing clinical trials.

Cyanoacrylate mesh fixation for laparoscopic inguinal hernia repair: a prospective, multicenter, single-arm study.

BACKGROUND: Inguinal hernia repair is among the most frequently performed surgical procedures. Alternatives to penetrating mesh fixation, such as surgical glue, are being investigated for their potential benefit in reducing chronic pain. The aim of this study was to assess the efficacy of the n-hexyl cyanoacrylate glue Ifabond™ for mesh fixation in laparoscopic inguinal hernia repair. METHODS: This prospective, multicenter, single-arm study collected data from laparoscopic inguinal hernia repairs using Ifabond™ (Peters Surgical, Boulogne-Billancourt Cedex, France) and a standard [Promesh® SURG ST (Peters Surgical)/Biomesh® P1 (Cousin Biotech, Wervicq-Sud, France)] or lightweight [Promesh® SURG LI (Peters Surgical)/Premium® Implant (Cousin Biotech)] polypropylene mesh. The primary endpoint was postoperative pain [100-scale Visual Analog Scale (VAS)]. Secondary endpoints were complications, hernia recurrences, and quality of life (QoL) (EQ-5D-3L health index and EQ-VAS). Patients were followed up at 5 weeks and 12 months after surgery. RESULTS: Six-hundred and thirteen patients underwent laparoscopic inguinal hernia repair. Postoperative pain decreased at 5-week (3.97 ± 10.04; p < 0.0001) and 12-month (3.83 ± 11.26; p < 0.0001) follow-up compared with before surgery (26.96 ± 19.42). One hundred and fifteen patients (13.74%) experienced chronic pain in the groin at 12-month follow-up, of whom 14 (2.67%) required analgesics. There were 6 patients with major morbidities and one patient died of an unrelated cause. Two hernia recurrences occurred within 12-month follow-up. Patients' QoL increased from an EQ-5D-3L index score of 0.82 ± 0.19 preoperatively to 0.90 ± 0.15 at 5 weeks (p < 0.0001) and 0.92 ± 0.15 at 12 months after surgery (p < 0.0001). The EQ-VAS general health scoring increased from 79.03 ± 12.69 preoperatively to 84.31 ± 9.97 at 5-week (p < 0.0001) and 84.16 ± 14.48 at 12-month follow-up (p < 0.0001). CONCLUSIONS: Ifabond™ (Peters Surgical) is a safe, reliable, and feasible fixation method for laparoscopic inguinal hernia repair with a very high surgeon satisfaction score, improved patients' QoL, and comparable risk of developing chronic pain and postoperative complications as described in the literature.

HIPEC Methodology and Regimens: The Need for an Expert Consensus.

BACKGROUND: Hyperthermic intraperitoneal chemotherapy (HIPEC) is performed with a wide variation in methodology, drugs, and other elements vital to the procedure. Adoption of a limited number of regimens could increase the collective experience of peritoneal oncologists, make comparison between studies more meaningful, and lead to a greater acceptance of results from randomized trials. This study aimed to determine the possibility of standardizing HIPEC methodology and regimens and to identify the best method of performing such a standardization. METHODS: A critical review of preclinical and clinical studies evaluating the pharmacokinetic aspects of different HIPEC drugs and drug regimens, the impact of hyperthermia, and the efficacy of various HIPEC regimens as well as studies comparing different regimens was performed. RESULTS: The preclinical and clinical data were limited, and studies comparing different regimens were scarce. Many of the regimens were neither supported by preclinical rationale or data nor validated by a dose-escalating formal phase 1 trial. All the regimens were based on pharmacokinetic data and did not take chemosensitivity of peritoneal metastases into account. Personalized medicine approaches such as patient-derived tumor organoids could offer a solution to this problem, although clinical validation is likely to be challenging. CONCLUSIONS: Apart from randomized trials, more translational research and phases 1 and 2 studies are needed. While waiting for better preclinical and clinical evidence, the best way to minimize heterogeneity is by an expert consensus that aims to identify and define a limited number of regimens for each indication and primary site. The choice of regimen then can be tailored to the patient profile and its expected toxicity and the methodology according regional factors.

Body surface area-based vs concentration-based perioperative intraperitoneal chemotherapy after optimal cytoreductive surgery in colorectal peritoneal surface malignancy treatment: COBOX trial.

BACKGROUND AND OBJECTIVES: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal perioperative chemotherapy (HIPEC) are the standard of care for patients diagnosed with colorectal peritoneal surface malignancy (PSM). Despite a clearly defined standardization of CRS, a large variety of HIPEC modalities are still used in clinical practice. METHODS: Body surface area (BSA)- and concentration-based HIPEC protocols were clinically and pharmacologically evaluated in a randomized phase III clinical pilot trial. Oxaliplatin dose was 460 mg/m 2 (BSA-based) in 2 L/m 2 carrier solution (concentration-based). Platinum quantification was performed using a validated inductively coupled plasma mass spectrometry method. Three-month morbidity, mortality, and health-related quality of life (HRQOL) were assessed. RESULTS: Thirty-one patients were randomized to either BSA- or concentration-based HIPEC. Toxicity and efficacy were higher (P < 0.001) in patients receiving concentration-based HIPEC. There was no difference in pharmacologic advantage between the two groups. A higher drug concentration in the tumor nodule at the end of HIPEC was found in the HIPEC-concentration group. There was no difference in major morbidity and mortality between the treatment groups. HRQOL was decreased 3 months postoperatively in the HIPEC-concentration group. CONCLUSION: Concentration-based chemotherapy delivers the drug in the most standardized way to the tumor nodule, resulting in increasing drug concentrations in the tumor nodule without increasing major morbidity.

Drugs, doses, and durations of intraperitoneal chemotherapy: standardising HIPEC and EPIC for colorectal, appendiceal, gastric, ovarian peritoneal surface malignancies and peritoneal mesothelioma.

Peritoneal surface malignancy (PSM) is a common manifestation of digestive and gynaecologic malignancies alike. At present, patients with isolated PSM are treated with a combination therapy of cytoreductive surgery (CRS) and hyperthermic peroperative intraperitoneal chemotherapy (HIPEC). The combination of CRS and intraperitoneal (IP) chemotherapy should now be considered standard of care for PSM from appendiceal epithelial cancers, colorectal cancer and peritoneal mesothelioma. Although there is a near universal standardisation regarding the CRS, we are still lacking a much-needed standardisation amongst the various IP chemotherapy treatment modalities used today in clinical practice. Pharmacologic evidence should be generated to answer important questions raised by the myriad of variables associated with IP chemotherapy.

Registries on peritoneal surface malignancies throughout the world, their use and their options.

AIM: The treatment of peritoneal surface malignancies ranges from palliative care to full cytoreductive surgery (CRS) and heated intraperitoneal chemotherapy, HIPEC. Ongoing monitoring of patient recruitment and volume is usually carried out through dedicated registries. With multiple registries available worldwide, we sought to investigate the nature, extent and value of existing worldwide CRS and HIPEC registries. METHODS: A questionnaire was sent out to all known major treatment centres. The questionnaire covers: general purpose of the registry; inclusion criteria in the registry; the date the registry was first established; volume of patients in the registry and description of the data fields in the registries. Finally, the population size of the catchment area of the registry was collected. RESULTS: Twenty-seven questionnaires where returned. National databases are established in northwest European countries. There are five international general databases. Most database collect data on patients who have undergone an attempt to CRS and HIPEC. Two registries collect data on all patients with peritoneal carcinomatosis regardless the treatment. Most registries are primarily used for tracking outcomes and complications. When correlating the number of cases of CRS and HIPEC that are performed to the catchment area of the various registry, a large variation in the number of performed procedures related to the overall population was noted, ranging from 1.3 to 57 patients/million year with an average of 15 patients/1 million year. CONCLUSIONS: CRS and HIPEC is a well-established treatment for peritoneal surface malignancies worldwide. However, the coverage as well as the registration of treatment procedures differs widely. The most striking difference is the proportion of HIPEC procedures per capita which ranges from 1.3 to 57 patients per million. This suggests either a difference in patient selection, lack of access to HIPEC centres or lack of appropriate data collection.

Laparoscopic ventral hernia repair using a composite mesh with polypropylene and expanded polytetrafluoroethylene: a prospective, multicentre registry.

BACKGROUND: Abdominal wall hernias are a common problem. Composite meshes placed intraperitoneally for abdominal wall hernia repair are widely used. This registry evaluated the safety and efficacy of one specific composite mesh with polypropylene and expanded polytetrafluoroethylene (Intramesh® T1) in laparoscopic ventral hernia repair. METHODS: A prospective multicentre registry with data from seven centres was collected between January 2013 and September 2014. Primary endpoint was recurrence rate at 12 months determined by clinical examination. Secondary outcome measures included intraoperative complications, complications during hospitalisation and at 1-month and 12-months follow-up. RESULTS: The registry included 90 patients (30 female and 60 male). Fifty-five patients (61.1%) presented with primary ventral hernias and 35 patients (38.9%) with incisional ventral hernias. Median hernia size was 4 cm2. Intraoperative complications were reported in two patients (2.2%). Complications during hospitalisation were reported in four (4.4%) patients. At 1-month follow-up, 17 (18.9%) patients had postoperative complications, of which 5 complications were major and 19 were minor. Late complications at 12-months were observed in 10 patients (11.1%), of which 2 were major and 8 minor complications. CONCLUSION: Intramesh® T1 is a safe and effective composite mesh with favourable short and midterm outcome and morbidity. (NCT01816867).

BEV-IP: Perioperative chemotherapy with bevacizumab in patients undergoing cytoreduction and intraperitoneal chemoperfusion for colorectal carcinomatosis.

BACKGROUND: Selected patients with peritoneal carcinomatosis (PC) from colorectal cancer (CRC) benefit from cytoreductive surgery (CRS) combined with intraperitoneal chemoperfusion (IPC). However, even after optimal cytoreduction, systemic and locoregional recurrence are common. Perioperative chemotherapy with bevacizumab (BEV) may improve the outcome of these patients. METHODS/DESIGN: The BEV-IP study is a phase II, single-arm, open-label study aimed at patients with colorectal or appendiceal adenocarcinoma with synchronous or metachronous PC. This study evaluates whether perioperative chemotherapy including BEV in combination with CRS and oxaliplatin-based IPC results in acceptable morbidity and mortality (primary composite endpoint). Secondary endpoints are treatment completion rate, chemotherapy-related toxicity, pathological response, progression free survival, and overall survival. DISCUSSION: The BEV-IP trial is the first prospective assessment of the safety and efficacy of perioperative chemotherapy combined with anti-angiogenic treatment in patients undergoing CRS and IPC for colorectal peritoneal metastases. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02399410 EudraCT number: 2015-001187-19 (registered March 9, 2015).

Peritoneal Surface Malignancies Originating From Urachal Carcinoma: Case Reports and Review of the Literature.

Urachal carcinoma (UC) is a rare and aggressive tumor arising from the urachal remnants, with the potential for peritoneal dissemination. Patients diagnosed with UC often have a poor prognosis. To date, there is no standardized treatment. Our objective is to present two cases of patients with peritoneal carcinomatosis (PC) secondary to an UC, who were treated with cytoreductive surgery (CRS) and hyperthermic peroperative intraperitoneal chemotherapy (HIPEC). A review of the literature on CRS and HIPEC in UC suggests CRS and HIPEC to be a safe and viable treatment option. Two patients with PC of UC underwent CRS and HIPEC in our institution. All available data were gathered and reported on. A literary search was carried out to find all available cases of patients with PC secondary to UC treated with CRS and HIPEC. Both patients underwent CRS and HIPEC and are currently free of recurrence. Literature research revealed nine other publications adding up to a total of 68 additional cases. CRS and HIPEC can provide satisfactory long-term oncological outcome with acceptable morbidity and mortality rates in patients with PC of urachal origin. It should be considered as a safe and feasible treatment option with curative potential.

Multi-omics Analysis Classifies Colorectal Cancer into Distinct Methylated Immunogenic and Angiogenic Subtypes Based on Anatomical Laterality.

We employed supervised machine learning algorithms to a cohort of colorectal cancer patients from the NCI to differentiate and classify the heterogenous disease based on anatomical laterality and multi-omics stratification, in a first of its kind. Multi-omics integrative analysis shows distinct clustering of left and right colorectal cancer with disentangled representation of methylome and delineation of transcriptome and genome. We present novel multi-omics findings consistent with augmented hypermethylation of genes in right CRC, epigenomic biomarkers on the right in conjunction with immune-mediated pathway signatures, and lymphocytic invasion which unlocks unique therapeutic avenues. Contrarily, left CRC multi-omics signature is found to be marked by angiogenesis, cadherins, and epithelial-mesenchymal transition (EMT). An integrated multi-omics molecular signature of RNF217-AS1, hsa-miR-10b, and panel of FBX02, FBX06, FBX044, MAD2L2, and MIIP copy number altered genes have been found by the study. Overall survival analysis reveals genomic biomarkers ABCA13 and TTN in 852 LCRC cases, and SOX11 in 170 RCRC cases that predicts a significant survival benefit. Our study exemplifies the translational competence and robustness of machine learning in effective translational bridging of research and clinic. Supplementary Information: The online version contains supplementary material available at 10.1007/s13193-023-01760-6.

The treatment of peritoneal carcinomatosis of colorectal cancer with complete cytoreductive surgery and hyperthermic intraperitoneal peroperative chemotherapy (HIPEC) with oxaliplatin: a Belgian multicentre prospective phase II clinical study.

BACKGROUND: Up to 25% of patients with metastatic colorectal cancer (CRC) present with peritoneal carcinomatosis (PC) as the only site of metastases. Complete cytoreductive surgery (CCRS) followed by hyperthermic intraperitoneal chemotherapy (HIPEC) aims for locoregional disease control and long-term survival. Oxaliplatin is effective for treating advanced CRC. This study assesses the safety and efficacy of CCRS with HIPEC with oxaliplatin for patients with PC of CRC. METHODS: A Belgian prospective multicenter registry was performed to monitor perioperative morbidity and assess mortality, disease-free survival (DFS), and overall survival (OS). RESULTS: Forty-eight consecutive patients underwent CCRS (R0/1) with HIPEC (male/female ratio 17/31, median age 60 years, range 24-76 years). Median PC index was 11 (range 1-22). Median operation time was 460 (range 125-840) min, with a median blood loss of 475 (range 2-6,000) ml. Thirty-day mortality was 0%. Complication rate (any grade) was 52.1%. Anastomotic leakage occurred in 10.4% of patients, bleeding in 6.3%, and bowel perforation in 2.1%. Median hospital stay was 20 (range 5-65) days. At median follow-up of 22.7 (range 3.2-55.7) months, OS was 97.9% [95% confidence interval (CI) 86.1-99.7] at 1 year and 88.7% (95% CI 73.6-95.4) at 2 years. DFS at 1 year was 65.8% (95% CI 52.3-76.2) and 45.5% (95% CI 34.3-55.9) at 2 years. Median time until recurrence was 19.8 months (95% CI 12-upper limit not defined). Only after dichotomizing PC index was a significant difference in OS found between low and high PC index. CONCLUSIONS: CCRS followed by HIPEC with oxaliplatin for PC from CRC can be implemented with acceptable morbidity. Long-term DFS and OS can be achieved in selected patients.

The many faces of intraperitoneal chemotherapy.

Cytoreductive surgery and intraperitoneal chemotherapy may offer chance for cure for patients with peritoneal metastasis. Many variations emerged, causing uncertainty when choosing the most suitable variant. By reviewing variability encountered in the management of peritoneal metastasis, we aim to raise awareness about this issue and hopefully initiate efforts to solve it. We review variance encountered in all aspects of this complex field of surgical oncology, indications, patient selection criteria, definition and extent of cytoreductive surgery and the numerous variables of intraperitoneal chemotherapy. Best benefit was achieved with pseudomyxoma peritonei, and to lesser extent in colorectal, ovarian and gastric cancer, but Indications keep expanding to include other tumors pathologies. Selection of patients depends on numerous prognostic indicators and criteria, according to tumor extent and pathology. The standard definition of cytoreductive surgery remains the same, but the boundaries of resection expand. Numerous chemotherapy regimens and administration methods are used, in search for best possible benefit. This variance must be reduced, to make the best use of, and further spread this treatment combination. Practical simple guidelines are needed for surgical oncologists willing to utilize this treatment for their patients, to be considered a true standard of care.

Evaluation of quality of clinical management of neuroendocrine tumors.

Background: Neuroendocrine tumors (NETs) are a group of biologically and clinically heterogeneous neoplasms predominantly found in the gastrointestinal and bronchopulmonary tractus. Despite a rising incidence, implementation of evidence-based standardized care for this heterogenous group remains challenging. The European Neuroendocrine Tumor Society regularly reviews guidelines regarding diagnostic and treatment strategies for NETs. The aim of this study is to shed light on the care of patients with a NET in Belgian Limburg, to provide data as a basis for future studies and to check whether data and results are according to consensus guidelines and outcomes described in literature. Methods: Our study concerned a detailed observational data collection of two large Belgian hospitals (Jessa Hospital Hasselt and Hospital Oost-Limburg Genk) with special interest in patient profile, quality of pathology reports, use of diagnostic imaging, and overall survival. Data on 188 patients were assembled between January 2010 and December 2014 with follow-up until June 2016 (median follow-up: 33.6 months). Results: Fifty percent of patients were male. NETs were located mainly in the digestive tract (63.8%) and lung (20.2%). Appendiceal NETs were diagnosed at a significantly younger age than other tumors (41.3 vs. 64.0 years). Overall, a mean pathology report quality score of 3.0/5 was observed with the highest scores for small bowel NETs. Diagnostic and nuclear imaging was performed in 74.5% and 29.8% of cases, respectively. Seventy-four percent of the population survived until the end of the observation period with highest survival rates for appendiceal and small bowel NETs. Conclusion: Overall, epidemiological results were comparable with findings in the literature. Gastrointestinal NETs met most of the requirements of qualitative pathology reporting and diagnostic imaging as listed in the European Neuroendocrine Tumor Society consensus guidelines. However, consensus with regard to bronchopulmonary NETs is still scarce and remains an objective for future research. Moreover, discussing treatment strategies in specialized multidisciplinary tumor boards would facilitate regional care.

Consensus statement for treatment protocols in pressurized intraperitoneal aerosol chemotherapy (PIPAC).

Objectives: Safe implementation and thorough evaluation of new treatments require prospective data monitoring and standardization of treatments. Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is a promising alternative for the treatment of patients with peritoneal disease with an increasing number of suggested drug regimens. The aim was to reach expert consensus on current PIPAC treatment protocols and to define the most important research topics. Methods: The expert panel included the most active PIPAC centers, organizers of PIPAC courses and principal investigators of prospective studies on PIPAC. A comprehensive literature review served as base for a two-day hybrid consensus meeting which was accompanied by a modified three-round Delphi process. Consensus bar was set at 70% for combined (strong and weak) positive or negative votes according to GRADE. Research questions were prioritized from 0 to 10 (highest importance). Results: Twenty-two out of 26 invited experts completed the entire consensus process. Consensus was reached for 10/10 final questions. The combination of doxorubicin (2.1 mg/m2) and cisplatin (10.5 mg/m2) was endorsed by 20/22 experts (90.9%). 16/22 (72.7%) supported oxaliplatin at 120 with potential reduction to 90 mg/m2 (frail patients), and 77.2% suggested PIPAC-Ox in combination with 5-FU. Mitomycin-C and Nab-paclitaxel were favoured as alternative regimens. The most important research questions concerned PIPAC conditions (n=3), standard (n=4) and alternative regimens (n=5) and efficacy of PIPAC treatment (n=2); 8/14 were given a priority of ≥8/10. Conclusions: The current consensus should help to limit heterogeneity of treatment protocols but underlines the utmost importance of further research.