New insights in the management of pseudomyxoma peritonei.

While a rare entity, peritoneal pseudomyxoma treatment evolves. Decision-making criteria improve with imaging development and exploratory laparoscopy. Surgery remains at the core of the therapeutic strategy whatever disease progression. Complete cytoreduction plus hyperthermic intraperitoneal chemotherapy (HIPEC) is standard of care. Iterative cytoreduction or debulking is sometimes justified. Intraperitoneal chemotherapy modalities change with early postoperative HIPEC or pressurized intraperitoneal aerosol chemotherapy. Systemic or local treatment such as new chemo/immuno-therapies or BromAc should improve outcomes. Expertise and multicentric cooperation are more than ever needed.

The clinical implications of staging laparoscopy in the diagnostic workup of gastric cancer patients: A population based study.

BACKGROUND: Since 2016, staging laparoscopy has been implemented in the diagnostic workup of patients with gastric cancer. Staging laparoscopy aims to detect incurable disease (peritoneal metastases and irresectable tumors) and to prevent futile laparotomies. METHODS: In this population-based nationwide study, we sought patient- and tumor characteristics associated with undergoing a staging laparoscopy. Additionally, we analyzed the prevalence of synchronous peritoneal metastases, the outcome of the staging laparoscopy and its clinical impact on treatment decisions. All patients diagnosed with non-cardia gastric cancer from the Netherlands Cancer Registry between 2016 and 2021 were included. RESULTS: Alongside tumor characteristics, patient characteristics such as younger age, absence of comorbidities and lower WHO performance status were associated with performing a staging laparoscopy. In the study period, an increase in the proportion of patients who underwent a staging laparoscopy was observed, from 19.6% in 2016 to 32.3% in 2021 (p-value<0.001). In the same period, the prevalence of synchronous peritoneal metastases increased from 25% to 31%. In 37.6% of the patients who had the outcome of their staging laparoscopy reported, had incurable disease diagnosed during staging laparoscopy. Significantly less of these patients were treated with triplet regimens as compared to patients with a negative staging laparoscopy (18.5 vs. 76.3%; p-value<0.001). CONCLUSION: The implementation of staging laparoscopy in gastric cancer patients paralleled the increase in diagnosis of incurable disease and a decrease in the application of triplet systemic therapies in these patients.

Recurrent disease detection after resection of pancreatic ductal adenocarcinoma using a recurrence-focused surveillance strategy (RADAR-PANC): protocol of an international randomized controlled trial according to the Trials within Cohorts design.

BACKGROUND: Disease recurrence remains one of the biggest concerns in patients after resection of pancreatic ductal adenocarcinoma (PDAC). Despite (neo)adjuvant systemic therapy, most patients experience local and/or distant PDAC recurrence within 2 years. High-level evidence regarding the benefits of recurrence-focused surveillance after PDAC resection is missing, and the impact of early detection and treatment of recurrence on survival and quality of life is unknown. In most European countries, recurrence-focused follow-up after surgery for PDAC is currently lacking. Consequently, guidelines regarding postoperative surveillance are based on expert opinion and other low-level evidence. The recent emergence of more potent local and systemic treatment options for PDAC recurrence has increased interest in early diagnosis. To determine whether early detection and treatment of recurrence can lead to improved survival and quality of life, we designed an international randomized trial. METHODS: This randomized controlled trial is nested within an existing prospective cohort in pancreatic cancer centers in the Netherlands (Dutch Pancreatic Cancer Project; PACAP) and the United Kingdom (UK) (Pancreas Cancer: Observations of Practice and survival; PACOPS) according to the "Trials within Cohorts" (TwiCs) design. All PACAP/PACOPS participants with a macroscopically radical resection (R0-R1) of histologically confirmed PDAC, who provided informed consent for TwiCs and participation in quality of life questionnaires, are included. Participants randomized to the intervention arm are offered recurrence-focused surveillance, existing of clinical evaluation, serum cancer antigen (CA) 19-9 testing, and contrast-enhanced computed tomography (CT) of chest and abdomen every three months during the first 2 years after surgery. Participants in the control arm of the study will undergo non-standardized clinical follow-up, generally consisting of clinical follow-up with imaging and serum tumor marker testing only in case of onset of symptoms, according to local practice in the participating hospital. The primary endpoint is overall survival. Secondary endpoints include quality of life, patterns of recurrence, compliance to and costs of recurrence-focused follow-up, and the impact on recurrence-focused treatment. DISCUSSION: The RADAR-PANC trial will be the first randomized controlled trial to generate high level evidence for the current clinical equipoise regarding the value of recurrence-focused postoperative surveillance with serial tumor marker testing and routine imaging in patients after PDAC resection. The Trials within Cohort design allows us to study the acceptability of recurrence-focused surveillance among cohort participants and increases the generalizability of findings to the general population. While it is strongly encouraged to offer all trial participants treatment at time of recurrence diagnosis, type and timing of treatment will be determined through shared decision-making. This might reduce the potential survival benefits of recurrence-focused surveillance, although insights into the impact on patients' quality of life will be obtained. TRIAL REGISTRATION: Clinicaltrials.gov, NCT04875325 . Registered on May 6, 2021.

Prediction of Isolated Local Recurrence After Resection of Pancreatic Ductal Adenocarcinoma: A Nationwide Study.

BACKGROUND: Distinguishing postoperative fibrosis from isolated local recurrence (ILR) after resection of pancreatic ductal adenocarcinoma (PDAC) is challenging. A prognostic model that helps to identify patients at risk of ILR can assist clinicians when evaluating patients' postoperative imaging. This nationwide study aimed to develop a clinically applicable prognostic model for ILR after PDAC resection. PATIENTS AND METHODS: An observational cohort study was performed, including all patients who underwent PDAC resection in the Netherlands (2014-2019; NCT04605237). On the basis of recurrence location (ILR, systemic, or both), multivariable cause-specific Cox-proportional hazard analysis was conducted to identify predictors for ILR and presented as hazard ratios (HRs) with 95% confidence intervals (CIs). A predictive model was developed using Akaike's Information Criterion, and bootstrapped discrimination and calibration indices were assessed. RESULTS: Among 1194/1693 patients (71%) with recurrence, 252 patients (21%) developed ILR. Independent predictors for ILR were resectability status (borderline versus resectable, HR 1.42; 95% CI 1.03-1.96; P = 0.03, and locally advanced versus resectable, HR 1.11; 95% CI 0.68-1.82; P = 0.66), tumor location (head versus body/tail, HR 1.50; 95% CI 1.00-2.25; P = 0.05), vascular resection (HR 1.86; 95% CI 1.41-2.45; P < 0.001), perineural invasion (HR 1.47; 95% CI 1.01-2.13; P = 0.02), number of positive lymph nodes (HR 1.04; 95% CI 1.01-1.08; P = 0.02), and resection margin status (R1 < 1 mm versus R0 ≥ 1 mm, HR 1.64; 95% CI 1.25-2.14; P < 0.001). Moderate performance (concordance index 0.66) with adequate calibration (slope 0.99) was achieved. CONCLUSIONS: This nationwide study identified factors predictive of ILR after PDAC resection. Our prognostic model, available through www.pancreascalculator.com , can be utilized to identify patients with a higher a priori risk of developing ILR, providing important information in patient evaluation and prognostication.

Perioperative Systemic Therapy Versus Cytoreductive Surgery and HIPEC Alone for Resectable Colorectal Peritoneal Metastases: Patient-Reported Outcomes of a Randomized Phase II Trial.

BACKGROUND: As part of a randomized phase II trial in patients with isolated resectable colorectal peritoneal metastases (CPMs), the present study compared patient-reported outcomes (PROs) of patients treated with perioperative systemic therapy versus cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) alone. Also, PROs of patients receiving perioperative systemic therapy were explored. PATIENTS AND METHODS: Eligible patients were randomized to perioperative systemic therapy (experimental) or CRS-HIPEC alone (control). PROs were assessed using EORTC QLQ-C30, QLQ-CR29, and EQ-5D-5L questionnaires at baseline, after neoadjuvant treatment (experimental), and at 3 and 6 months postoperatively. Linear mixed modeling was used to compare five predefined PROs (visual analog scale, global health status, physical functioning, fatigue, C30 summary score) between arms and to longitudinally analyze PROs in the experimental arm. RESULTS: Of 79 analyzed patients, 37 (47%) received perioperative systemic therapy. All predefined PROs were comparable between arms at all timepoints and returned to baseline at 3 or 6 months postoperatively. The experimental arm had worsening of fatigue [mean difference (MD) + 14, p = 0.001], loss of appetite (MD + 15, p = 0.003), hair loss (MD + 18, p < 0.001), and loss of taste (MD + 27, p < 0.001) after neoadjuvant treatment. Except for loss of appetite, these PROs returned to baseline at 3 or 6 months postoperatively. CONCLUSIONS: In patients with resectable CPM randomized to perioperative systemic therapy or CRS-HIPEC alone, PROs were comparable between arms and returned to baseline postoperatively. Together with the trial's previously reported feasibility and safety data, these findings show acceptable tolerability of perioperative systemic therapy in this setting.

Role Of Ovarian Metastases In Colorectal Cancer (ROMIC): a Dutch study protocol to evaluate the effect of prophylactic salpingo-oophorectomy in postmenopausal women.

BACKGROUND: The mean incidence of ovarian metastases (OM) in patients with colorectal cancer (CRC) is 3.4%. The 5-year survival of these patients, even when operated with curative intent, is remarkably low. The lifetime risk of ovarian cancer is approximately 1.3%. Prophylactic salpingo-oophorectomy (PSO, or surgical removal of the ovaries and fallopian tubes) could reduce the number of CRC patients that develop OM after removal of the primary tumor, as well as preventing the occurrence of primary ovarian cancer. Recently, the care pathway for CRC has been changed in several hospitals in line with the updated Dutch guideline. The possibility of PSO is now discussed with postmenopausal CRC patients in these hospitals. The aims of the current study are firstly to estimate the incidence of OM and primary ovarian cancer in postmenopausal patients with CRC, and secondly to evaluate the effect of PSO in these patients. METHODS: An information bulletin and decision guide on this topic was implemented in several Dutch hospitals in 2020. Post-decision outcomes will be collected prospectively. The study population consists of postmenopausal (≥ 60 years of age) patients that are operated with curative intent for CRC. Based on their own preference, patients will be divided into two groups: those who choose to undergo PSO and those who do not. The main study parameters are the reduction in incidence of ovarian malignancies (metastatic or primary) following PSO, and the number needed to treat (NNT) by PSO to prevent one case of ovarian malignancy. DISCUSSION: This will be the first study to evaluate the effect of PSO in postmenopausal CRC patients that is facilitated by an altered CRC care pathway. The results of this study are expected to provide relevant information on whether PSO adds significant value to postmenopausal patients with CRC. TRIAL REGISTRATION: International Clinical Trials Registry Platform, NL7870. Registered on 2019 July 12. URL of trial registry record: https://trialsearch.who.int/Trial2.aspx?TrialID=NL7870 . PROTOCOL VERSION: 1.0, date 2021 June 8.

Ovarian metastases in young women with colorectal cancer: a retrospective multicenter cohort study.

BACKGROUND AND PURPOSE: Previous studies indicated that approximately 3.4% of female colorectal cancer (CRC) patients are at increased risk of developing ovarian metastases (OM). It has been suggested that young women more frequently develop this form of metastatic disease. METHODS: This study evaluated, in 6 Dutch hospitals, the proportion of young women with CRC who developed OM. RESULTS: In a cohort of 200 young (age ≤ 55) women with CRC, the proportion of patients diagnosed with synchronous or metachronous OM was calculated. This study revealed that 5% (n = 10) of young female CRC patients developed ovarian metastases resulting in a 5-year overall survival rate of approximately 40%. Furthermore, six patients had concurrent peritoneal metastases, five patients had bilateral ovarian metastases, and five patients had synchronous metastases, while the median time of the occurrence of metachronous metastases (n = 5) was 19 months. CONCLUSION: This retrospective multicenter cohort study indicates that 5% of young women with CRC either present with or develop OM. This result appears to be clinically relevant and demonstrates the need for improved surveillance for young women diagnosed with CRC.

Primary ovarian cancer after colorectal cancer: a Dutch nationwide population-based study.

BACKGROUND AND PURPOSE: Women with colorectal cancer (CRC) are at risk not only of developing ovarian metastases, but also of developing a primary ovarian malignancy. Several earlier studies have in fact shown a link between the development of primary ovarian cancer and CRC. The purpose of this study was therefore to determine the risk of developing a primary ovarian cancer in women with prior CRC compared to the general population. METHODS: Data from the Netherlands Cancer Registry were used. All women diagnosed with invasive CRC between 1989 and 2017 were included. Standardized incidence ratios (SIRs) and absolute excess risks (AERs) per 10,000 person-years were calculated. RESULTS: During the study period, 410 (0.3%) CRC patients were diagnosed with primary ovarian cancer. Women with CRC had a 20% increased risk of developing ovarian cancer compared to the general population (SIR = 1.2, 95% CI: 1.1-1.3). The AER of ovarian cancer was 0.9 per 10,000 person-years. The risk was especially increased within the first year of a CRC diagnosis (SIR = 3.3, 95% CI: 2.8-3.8) and in women aged ≤ 55 years (SIR = 2.0, 95% CI: 1.6-2.6). CONCLUSION: This study found a slightly increased risk of primary ovarian cancer in women diagnosed with CRC compared to the general population. However, this may be partly attributable to surveillance or detection bias. Nevertheless, our findings could be helpful for patient counseling, as CRC patients do not currently receive information concerning the increased risk of ovarian cancer.

Peritoneal metastases in elderly patients with colorectal cancer.

BACKGROUND: With the introduction of cytoreductive surgery with intraperitoneal chemotherapy and the development of new systemic anti-cancer agents, the treatment of colorectal cancer (CRC) patients with peritoneal metastases has changed. Real-world data on the treatment of elderly patients and their clinical outcomes is lacking. METHODS: All CRC patients diagnosed with synchronous peritoneal metastases (SPM) during 2008-2019 (n = 7,748) were identified from the Netherlands Cancer Registry. Trends in treatment and postoperative mortality were described by age category (<70, 70-74, 75-79, ≥80 years) and period of diagnosis (2008-2013, 2014-2019). Kaplan-Meier curves were constructed, and log-rank tests were performed to evaluate differences in overall survival (OS). RESULTS: With increasing age, less patients received multimodality treatment and systemic treatment. Of the patients aged <70 years, 38% underwent multimodality treatment and 35% palliative systemic therapy, declining to 4% and 12% in patients ≥80 years. A large and increasing proportion of elderly patients did not receive cancer-directed treatment, this increased from 32% in 2008-2013 to 41% in 2014-2019 in 75-79 years old patients and from 52% to 65% in ≥80 years old. Postoperative mortality decreased in all age categories over time, OS remained stable. The median OS of elderly patients ranged from 8 months in 70-74 years old to 3 months in patients aged ≥80 years. DISCUSSION: Age strongly affects treatment of patients with SPM, with a large and increasing proportion of elderly patients not receiving cancer-directed treatment. Their prognosis remains very poor. There is a need for therapeutic options that are well tolerable for elderly patients.

Impact of nationwide centralization of oesophageal, gastric, and pancreatic surgery on travel distance and experienced burden in the Netherlands.

BACKGROUND: This study aims to assess the impact of nationwide centralization of surgery on travel distance and travel burden among patients with oesophageal, gastric, and pancreatic cancer according to age in the Netherlands. As centralization of care increases to improve postoperative outcomes, travel distance and experienced burden might increase. MATERIALS AND METHODS: All patients who underwent surgery between 2006 and 2017 for oesophageal, gastric and pancreatic cancer in the Netherlands were included. Travel distance between patient's home address and hospital of surgery in kilometres was calculated. Questionnaires were used to assess experienced travel burden in a subpopulation (n = 239). Multivariable ordinal logistic regression models were constructed to identify predictors for longer travel distance. RESULTS: Over 23,838 patients were included, in whom median travel distance for surgical care increased for oesophageal cancer (n = 9217) from 18 to 28 km, for gastric cancer (n = 6743) from 9 to 26 km, and for pancreatic cancer (n = 7878) from 18 to 25 km (all p < 0.0001). Multivariable analyses showed an increase in travel distance for all cancer types over time. In general, patients experienced a physical and social burden, and higher financial costs, due to traveling extra kilometres. Patients aged >70 years travelled less often independently (56% versus 68%), as compared to patients aged ≤70 years. CONCLUSION: With nationwide centralization, travel distance increased for patients undergoing oesophageal, gastric, and pancreatic cancer surgery. Younger patients travelled longer distances and experienced a lower travel burden, as compared to elderly patients. Nevertheless, on a global scale, travel distances in the Netherlands remain limited.

Dedicated MRI staging versus surgical staging of peritoneal metastases in colorectal cancer patients considered for CRS-HIPEC; the DISCO randomized multicenter trial.

BACKGROUND: Selecting patients with peritoneal metastases from colorectal cancer (CRCPM) who might benefit from cytoreductive surgery followed by hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) is challenging. Computed tomography generally underestimates the peritoneal tumor load. Diagnostic laparoscopy is often used to determine whether patients are amenable for surgery. Magnetic resonance imaging (MRI) has shown to be accurate in predicting completeness of CRS. The aim of this study is to determine whether MRI can effectively reduce the need for surgical staging. METHODS: The study is designed as a multicenter randomized controlled trial (RCT) of colorectal cancer patients who are deemed eligible for CRS-HIPEC after conventional CT staging. Patients are randomly assigned to either MRI based staging (arm A) or to standard surgical staging with or without laparoscopy (arm B). In arm A, MRI assessment will determine whether patients are eligible for CRS-HIPEC. In borderline cases, an additional diagnostic laparoscopy is advised. The primary outcome is the number of unnecessary surgical procedures in both arms defined as: all surgeries in patients with definitely inoperable disease (PCI > 24) or explorative surgeries in patients with limited disease (PCI < 15). Secondary outcomes include correlations between surgical findings and MRI findings, cost-effectiveness, and quality of life (QOL) analysis. CONCLUSION: This randomized trial determines whether MRI can effectively replace surgical staging in patients with CRCPM considered for CRS-HIPEC. TRIAL REGISTRATION: Registered in the clinical trials registry of U.S. National Library of Medicine under NCT04231175 .

Total neoadjuvant FOLFIRINOX versus neoadjuvant gemcitabine-based chemoradiotherapy and adjuvant gemcitabine for resectable and borderline resectable pancreatic cancer (PREOPANC-2 trial): study protocol for a nationwide multicenter randomized controlled trial.

BACKGROUND: Neoadjuvant therapy has several potential advantages over upfront surgery in patients with localized pancreatic cancer; more patients receive systemic treatment, fewer patients undergo futile surgery, and R0 resection rates are higher, thereby possibly improving overall survival (OS). Two recent randomized trials have suggested benefit of neoadjuvant chemoradiotherapy over upfront surgery, both including single-agent chemotherapy regimens. Potentially, the multi-agent FOLFIRINOX regimen (5-fluorouracil with leucovorin, irinotecan, and oxaliplatin) may further improve outcomes in the neoadjuvant setting for localized pancreatic cancer, but randomized studies are needed. The PREOPANC-2 trial investigates whether neoadjuvant FOLFIRINOX improves OS compared with neoadjuvant gemcitabine-based chemoradiotherapy and adjuvant gemcitabine in resectable and borderline resectable pancreatic cancer patients. METHODS: This nationwide multicenter phase III randomized controlled trial includes patients with pathologically confirmed resectable and borderline resectable pancreatic cancer with a WHO performance score of 0 or 1. Resectable pancreatic cancer is defined as no arterial and ≤ 90 degrees venous involvement; borderline resectable pancreatic cancer is defined as ≤90 degrees arterial and ≤ 270 degrees venous involvement without occlusion. Patients receive 8 cycles of neoadjuvant FOLFIRINOX chemotherapy followed by surgery without adjuvant treatment (arm A), or 3 cycles of neoadjuvant gemcitabine with hypofractionated radiotherapy (36 Gy in 15 fractions) during the second cycle, followed by surgery and 4 cycles of adjuvant gemcitabine (arm B). The primary endpoint is OS by intention-to-treat. Secondary endpoints include progression-free survival, quality of life, resection rate, and R0 resection rate. To detect a hazard ratio of 0.70 with 80% power, 252 events are needed. The number of events is expected to be reached after inclusion of 368 eligible patients assuming an accrual period of 3 years and 1.5 years follow-up. DISCUSSION: The PREOPANC-2 trial directly compares two neoadjuvant regimens for patients with resectable and borderline resectable pancreatic cancer. Our study will provide evidence on the neoadjuvant treatment of choice for patients with resectable and borderline resectable pancreatic cancer. TRIAL REGISTRATION: Primary registry and trial identifying number: EudraCT: 2017-002036-17 . Date of registration: March 6, 2018. Secondary identifying numbers: The Netherlands National Trial Register - NL7094 , NL61961.078.17, MEC-2018-004.

Effect of centralization and regionalization of pancreatic surgery on resection rates and survival.

BACKGROUND: Centralization of pancreatic surgery in the Netherlands has been ongoing since 2011. The aim of this study was to assess how centralization has affected the likelihood of resection and survival of patients with non-metastatic pancreatic head and periampullary cancer, diagnosed in hospitals with and without pancreatic surgery services. METHODS: An observational cohort study was performed on nationwide data from the Netherlands Cancer Registry (2009-2017), including patients diagnosed with non-metastatic pancreatic head or periampullary cancer. The period of diagnosis was divided into three time intervals: 2009-2011, 2012-2014 and 2015-2017. Hospital of diagnosis was classified as a pancreatic or non-pancreatic surgery centre. Analyses were performed using multivariable logistic and Cox regression models. RESULTS: In total, 10 079 patients were included, of whom 3114 (30.9 per cent) were diagnosed in pancreatic surgery centres. Between 2009-2011 and 2015-2017, the number of patients undergoing resection increased from 1267 of 3169 (40.0 per cent) to 1705 of 3566 (47.8 per cent) (P for trend < 0.001). In multivariable analysis, in 2015-2017, unlike the previous periods, patients diagnosed in pancreatic and non-pancreatic surgery centres had a similar likelihood of resection (odds ratio 1.08, 95 per cent c.i. 0.90 to 1.28; P = 0.422). In this period, however, overall survival was higher in patients diagnosed in pancreatic surgery than in those diagnosed in non-pancreatic surgery centres (hazard ratio 0.92, 95 per cent c.i. 0.85 to 0.99; P = 0.047). CONCLUSION: After centralization of pancreatic surgery, the resection rate for patients with pancreatic head and periampullary cancer diagnosed in non-pancreatic surgery centres increased and became similar to that in pancreatic surgery centres. Overall survival remained higher in patients diagnosed in pancreatic surgery centres.

Extensive diagnostic work-up for patients with carcinoma of unknown primary.

Patients with carcinoma of unknown primary (CUP) present with metastatic disease without an identified primary tumour. The unknown site of origin makes the diagnostic work-up and treatment challenging. Since little information is available regarding diagnostic work-up and treatment in daily practice, we collected and analysed these in a patient cohort with regard to the recommendations of the national CUP guideline. Data of 161 patients diagnosed with CUP in 2014 or 2015 were extracted from the Netherlands Cancer Registry (NCR) and supplemented with diagnostic work-up information from patient files and analysed. Patients underwent an average of five imaging studies during the diagnostic phase (range 1-17). From the tests as recommended in the national guideline on CUP, a chest X-ray was most commonly performed (73%), whereas a PET-CT was done in one out of four patients (24%). Biopsies were taken in 86% of the study population, with Cytokeratin 7 being the most frequently tested histopathological marker (73%). Less than half of patients received therapy (42%). CUP patients undergo extensive diagnostic work-up. The performance status did not influence the extent of the diagnostic work-up in CUP patients, but it was an important factor for receiving treatment.

Appendiceal tumours and pseudomyxoma peritonei: Literature review with PSOGI/EURACAN clinical practice guidelines for diagnosis and treatment.

Pseudomyxoma Peritonei (PMP) is a rare peritoneal malignancy, most commonly originating from a perforated epithelial tumour of the appendix. Given its rarity, randomized controlled trials on treatment strategies are lacking, nor likely to be performed in the foreseeable future. However, many questions regarding the management of appendiceal tumours, especially when accompanied by PMP, remain unanswered. This consensus statement was initiated by members of the Peritoneal Surface Oncology Group International (PSOGI) Executive Committee as part of a global advisory role in the management of uncommon peritoneal malignancies. The manuscript concerns an overview and analysis of the literature on mucinous appendiceal tumours with, or without, PMP. Recommendations are provided based on three Delphi voting rounds with GRADE-based questions amongst a panel of 80 worldwide PMP experts.

The Delphi and GRADE methodology used in the PSOGI 2018 consensus statement on Pseudomyxoma Peritonei and Peritoneal Mesothelioma.

Pseudomyxoma Peritonei (PMP) and Peritoneal Mesothelioma (PM) are both rare peritoneal malignancies. Currently, affected patients may be treated with Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy offering long-term survival or even cure in selected patients. However, many issues regarding the optimal treatment strategy are currently under debate. To aid physicians involved in the treatment of these patients in clinical decision making, the PSOGI executive committee proposed to create a consensus statement on PMP and PM. This manuscript describes the methodology of the consensus process. The Delphi technique is a reliable method for attaining consensus on a topic that lacks scientific evidence through multiple voting rounds which feeds back responses to the participants in between rounds. The GRADE system provides a structured framework for presenting and grading the available evidence. Separate questionnaires were created for PMP and PM and sent during two voting rounds to 80 and 38 experts, respectively. A consensus threshold of 51.0% was chosen. After the second round, consensus was reached on 92.9%-100.0% of the questions. The results were presented and discussed in the plenary session at the PSOGI 2018 international meeting in Paris. A third round for the remaining issues is currently in progress. In conclusion, using the Delphi technique and GRADE methodology, consensus was reached in many issues regarding the treatment of PM and PMP amongst an international panel of experts. The main results will be published in the near future.