Unleashing the efficacy of immune checkpoint inhibitors for advanced hepatocellular carcinoma: factors, strategies, and ongoing trials.

Hepatocellular carcinoma (HCC) is a prevalent primary liver cancer, representing approximately 85% of cases. The diagnosis is often made in the middle and late stages, necessitating systemic treatment as the primary therapeutic option. Despite sorafenib being the established standard of care for advanced HCC in the past decade, the efficacy of systemic therapy remains unsatisfactory, highlighting the need for novel treatment modalities. Recent breakthroughs in immunotherapy have shown promise in HCC treatment, particularly with immune checkpoint inhibitors (ICIs). However, the response rate to ICIs is currently limited to approximately 15%-20% of HCC patients. Recently, ICIs demonstrated greater efficacy in "hot" tumors, highlighting the urgency to devise more effective approaches to transform "cold" tumors into "hot" tumors, thereby enhancing the therapeutic potential of ICIs. This review presented an updated summary of the factors influencing the effectiveness of immunotherapy in HCC treatment, identified potential combination therapies that may improve patient response rates to ICIs, and offered an overview of ongoing clinical trials focusing on ICI-based combination therapy.

Trial watch: immunotherapeutic strategies on the horizon for hepatocellular carcinoma.

The use of immune checkpoint inhibitors (ICIs) targeting PD-L1/PD-1 and CTLA-4 has transformed the oncology practice of hepatocellular carcinoma. However, only 25-30% of the patients with advanced HCC treated with atezolizumab-bevacizumab or tremelimumab-durvalumab (STRIDE) respond initially, and mechanistic biomarkers and novel treatment strategies are urgently needed for patients who present with or acquire resistance to first-line ICI-based therapies. The recent approval of the STRIDE regimen has also engendered new questions, such as patient selection factors (e.g. portal hypertension and history of variceal bleed) and biomarkers, and the optimal combination and sequencing of ICI-based regimens. Triumphs in the setting of advanced HCC have also galvanized considerable interest in the broader application of ICIs to early- and intermediate-stage diseases, including clinical combination of ICIs with locoregional therapies. Among these clinical contexts, the role of ICIs in liver transplantation - which is a potentially curative strategy unique to HCC management - as a bridge to liver transplant in potential candidates or in the setting of post-transplant recurrence, warrants investigation in view of the notable theoretical risk of allograft rejection. In this review, we summarize and chart the landscape of seminal immuno-oncology trials in HCC and envision future clinical developments.

A Phase I, First-in-Human Study of PRL3-zumab in Advanced, Refractory Solid Tumors and Hematological Malignancies.

BACKGROUND: Phosphatase of regenerating liver-3 (PRL-3) is involved in cellular processes driving metastasis, cell proliferation, invasion, motility and survival. It has been shown to be upregulated and overexpressed in cancer tissue, in contrast to low or no expression in most normal tissue. PRL3-zumab is a first-in-class humanized antibody that specifically binds to PRL-3 oncotarget with high affinity and has been shown to reduce tumor growth and increase survival. OBJECTIVE: In the study, we aimed to determine the safety and efficacy of PRL3-zumab in patients with advanced solid tumors and hematological malignancies. METHODS: We conducted a phase I, first-in-human study in advanced solid tumors and hematological malignancies to investigate the safety, tolerability and efficacy of PRL3-zumab. Response rates were evaluated using the Response Evaluation Criteria in Solid Tumors (RECIST) guideline (version 1.1) for solid tumors. For acute myeloid leukemia (AML) patients, bone marrow response criteria based on the European Leukaemia Network (ELN) 2017 guidelines for AML were used. We also explored the pharmacokinetics and pharmacodynamic relationships of PRL3-zumab in patients. This study was registered with ClinicalTrials.gov: NCT03191682. RESULTS: In the dose-escalation cohort, 11 patients with advanced solid tumors were enrolled into the study. An additional 12 patients with solid tumors and four patients with AML were enrolled in the dose-expansion cohort. Maximum tolerability was not achieved in this study, as there were no dose-limiting toxicities. Potential treatment-emergent adverse events were grade 1 increased stoma output and fatigue and grade 2 vomiting. Best response observed was stable disease in three solid-tumor patients (11.1%). The pharmacokinetics of PRL3-zumab were dose proportional, consistent with an IgG type monoclonal antibody. CONCLUSIONS: PRL3-zumab, a first-in-class humanized antibody, was safe and tolerable in solid tumors and hematological malignancies.

Comprehensive molecular phenotyping of ARID1A-deficient gastric cancer reveals pervasive epigenomic reprogramming and therapeutic opportunities.

OBJECTIVE: Gastric cancer (GC) is a leading cause of cancer mortality, with ARID1A being the second most frequently mutated driver gene in GC. We sought to decipher ARID1A-specific GC regulatory networks and examine therapeutic vulnerabilities arising from ARID1A loss. DESIGN: Genomic profiling of GC patients including a Singapore cohort (>200 patients) was performed to derive mutational signatures of ARID1A inactivation across molecular subtypes. Single-cell transcriptomic profiles of ARID1A-mutated GCs were analysed to examine tumour microenvironmental changes arising from ARID1A loss. Genome-wide ARID1A binding and chromatin profiles (H3K27ac, H3K4me3, H3K4me1, ATAC-seq) were generated to identify gastric-specific epigenetic landscapes regulated by ARID1A. Distinct cancer hallmarks of ARID1A-mutated GCs were converged at the genomic, single-cell and epigenomic level, and targeted by pharmacological inhibition. RESULTS: We observed prevalent ARID1A inactivation across GC molecular subtypes, with distinct mutational signatures and linked to a NFKB-driven proinflammatory tumour microenvironment. ARID1A-depletion caused loss of H3K27ac activation signals at ARID1A-occupied distal enhancers, but unexpectedly gain of H3K27ac at ARID1A-occupied promoters in genes such as NFKB1 and NFKB2. Promoter activation in ARID1A-mutated GCs was associated with enhanced gene expression, increased BRD4 binding, and reduced HDAC1 and CTCF occupancy. Combined targeting of promoter activation and tumour inflammation via bromodomain and NFKB inhibitors confirmed therapeutic synergy specific to ARID1A-genomic status. CONCLUSION: Our results suggest a therapeutic strategy for ARID1A-mutated GCs targeting both tumour-intrinsic (BRD4-assocatiated promoter activation) and extrinsic (NFKB immunomodulation) cancer phenotypes.

Volatile organic compounds as potential biomarkers of irritable bowel syndrome: A systematic review.

BACKGROUND: Irritable bowel syndrome (IBS) is a prevalent gastrointestinal disease characterized by intermittent abdominal pain with altered bowel habits. Due to the condition's chronicity, patients suffer from poor quality of life, while the healthcare burden continues to grow. There is currently no reliable biomarker for the diagnosis of IBS, and the current approach depends on ruling-out organic diseases such as inflammatory bowel disease (IBD) and colorectal cancer by markers of inflammation like fecal calprotectin and C-reactive protein, or invasive procedures like a colonoscopy. Volatile organic compounds (VOCs) are growing in popularity as a biomarker due to its accuracy and ease of use. PURPOSE: This systematic review of Medline and Cochrane's databases aimed to identify VOCs in the diagnosis of IBS. 57% of the studies proved that VOCs could identify IBS patients from healthy controls with AUC ranging from 0.83 to 0.99. Studies that distinguished IBS from IBD patients had slightly higher AUC of 0.87-0.98. Combining VOC into panels allowed the creation of discriminative algorithms. Though current research is limited by areas of heterogeneity in VOC sampling and small sample sizes, our review shows that VOC analysis has the potential to be a noninvasive point-of-care test that differentiates IBS from other organic gastrointestinal diseases.

Clinical relevance of PD-1 positive CD8 T-cells in gastric cancer.

BACKGROUND: We evaluated the relevance of PD-1+CD8+ T-cells in gastric cancer (GC) including prognostic significance, association with chemotherapy and immunotherapy sensitivity and correlations with the tumor microenvironment (TME). METHODS: Discovery cohort: GC samples were evaluated for AE1/3, CD8, PD-1, Ki-67 and Granzyme-B expression with fluorescence-based multiplex immunohistochemistry (mIHC). Validation cohorts: we analyzed bulk RNAseq GC datasets from TCGA, the "3G" chemotherapy trial and an immunotherapy phase 2 trial. The cox proportional hazards model was used to identify factors that influenced overall survival (OS). To study the TME, we analyzed single-cell RNAseq performed on GCs. RESULTS: In the discovery cohort of 350 GCs, increased PD-1 expression of CD8 T-cells was prognostic for OS (HR 0.822, p = 0.042). PD-1 expression in CD8 T-cells highly correlated with cytolytic [Granzyme-B+] (r = 0.714, p < 0.001) and proliferative [Ki-67+] (r = 0.798, p < 0.001) activity. Analysis of bulk RNAseq datasets showed tumors with high PD-1 and CD8A expression levels had improved OS when treated with immunotherapy (HR 0.117, p = 0.036) and chemotherapy (HR 0.475, p = 0.017). Analysis of an scRNAseq dataset of 152,423 cells from 40 GCs revealed that T-cell and NK-cell proportions were higher (24% vs 18% and 19% vs 15%, p < 0.0001), while macrophage proportions were lower (7% vs 11%, p < 0.0001) in CD8PD-1high compared to CD8PD-1low tumors. CONCLUSION: This is one of the largest GC cohorts of mIHC combined with analysis of multiple datasets providing orthogonal validation of the clinical relevance of PD-1+CD8+ T-cells being associated with improved OS. CD8PD-1high tumors have distinct features of an immunologically active, T-cell inflamed TME.

Clinical outcome and prognostic factors for Asian patients in Phase I clinical trials.

BACKGROUND: Patient selection is key in Phase I studies, and prognosis can be difficult to estimate in heavily pre-treated patients. Previous prognostic models like the Royal Marsden Hospital (RMH) score or using the neutrophil-lymphocyte ratio (NLR) have not been validated in current novel therapies nor in the Asian Phase I population. METHODS: We conducted a retrospective review of 414 patients with solid tumours participating in Phase I studies at our centre between October 2013 and December 2020. RESULTS: The RMH model showed poorer prognosis with increasing scores [RMH score 1, HR 1.28 (95% CI: 0.96-1.70); RMH score 2, HR 2.27 (95% CI: 1.62-3.17); RMH score 3, HR 4.14 (95% CI: 2.62-6.53)]. NLR did not improve the AUC of the model. Poorer ECOG status (ECOG 1 vs. 0: HR = 1.59 (95% CI = 1.24-2.04), P < 0.001) and primary tumour site (GI vs. breast cancer: HR = 3.06, 95% CI = 2.16-4.35, P < 0.001) were prognostic. CONCLUSIONS: We developed a NCIS prognostic score with excellent prognostic ability for both short-term and longer-term survival (iAUC: 0.71 [95% CI 0.65-0.76]), and validated the RMH model in the largest Asian study to date.

FAM3C in circulating tumor-derived extracellular vesicles promotes non-small cell lung cancer growth in secondary sites.

Rationale: Metastasis is a complex process with a molecular underpinning that remains unclear. We hypothesize that cargo proteins conducted by extracellular vesicles (EVs) released from tumors may confer growth and metastasis potential on recipient cells. Here, we report that a cytokine-like secreted protein, FAM3C, contributes to late-stage lung tumor progression. Methods: EV protein profiling was conducted with an unbiased proteomic mass spectrometry analysis on non-small cell lung cancer (NSCLC) and normal lung fibroblast cell lines. Expression of FAM3C was confirmed in a panel of NSCLC cell lines, and correlated to the invasive and metastatic potentials. Functional phenotype of endogenous FAM3C and tumor-derived EVs (TDEs) were further investigated using various biological approaches in RNA and protein levels. Metastasis potential of TDEs secreted by FAM3C-overexpressing carcinoma cells was validated in mouse models. Results: Transcriptomic meta-analysis of pan-cancer datasets confirmed the overexpression of FAM3C - a gene encoding for interleukin-like EMT inducer (ILEI) - in NSCLC tumors, with strong association with poor patient prognosis and cancer metastasis. Aberrant expression of FAM3C in lung carcinoma cells enhances cellular transformation and promotes distant lung tumor colonization. In addition, higher FAM3C concentrations were detected in EVs extracted from plasma samples of NSCLC patients compared to those of healthy subjects. More importantly, we defined a hitherto-unknown mode of microenvironmental crosstalk involving FAM3C in EVs, whereby the delivery and uptake of FAM3C via TDEs enhances oncogenic signaling - in recipient cells that phenocopies the cell-endogenous overexpression of FAM3C. The oncogenicity transduced by FAM3C is executed via a novel interaction with the Ras-related protein RalA, triggering the downstream activation of the Src/Stat3 signaling cascade. Conclusions: Our study describes a novel mechanism for FAM3C-driven carcinogenesis and shed light on EV FAM3C as a driver for metastatic lung tumors that could be exploited for cancer therapeutics.

Pembrolizumab in Asian patients with microsatellite-instability-high/mismatch-repair-deficient colorectal cancer.

The phase 3 KEYNOTE-177 study evaluated pembrolizumab versus chemotherapy with or without bevacizumab or cetuximab in patients with newly diagnosed, microsatellite-instability-high (MSI-H)/mismatch-repair-deficient (dMMR) metastatic colorectal cancer (mCRC). Primary endpoints were progression-free survival (PFS) per RECIST v1.1 by blinded independent central review (BICR) and overall survival (OS). Secondary endpoints were overall response rate (ORR) per RECIST v1.1 by BICR and safety. Here, we report results from the post hoc analysis of patients who were enrolled in Asia from the final analysis (FA) of KEYNOTE-177. A total of 48 patients from Japan, Korea, Singapore, and Taiwan (pembrolizumab, n = 22; chemotherapy, n = 26) were included. At FA, median time from randomization to data cutoff (February 19, 2021) was 45.3 (range 38.1-57.8) months with pembrolizumab and 43.9 (range 36.6-55.1) months with chemotherapy. Median PFS was not reached (NR; 95% confidence interval [CI] 1.9 months-NR) with pembrolizumab versus 10.4 (95% CI 6.3-22.0) months with chemotherapy (hazard ratio [HR] 0.56, 95% CI 0.26-1.20). Median OS was NR (range 13.8 months-NR) versus 30.0 (14.7-NR) months (HR 0.65, 95% CI 0.27-1.55) and ORR was 50% (95% CI 28-72) versus 46% (95% CI 27-67). Grade 3/4 treatment-related adverse events (TRAEs) were reported by two patients (9%) in the pembrolizumab arm and 20 (80%) in the chemotherapy arm. Immune-mediated adverse events or infusion reactions were reported by six patients (27%) and 10 patients (40%), respectively. No deaths due to TRAEs occurred. These data support first-line pembrolizumab as a standard of care for patients from Asia with MSI-H/dMMR mCRC. ClinicalTrials.gov identifier: NCT02563002.

Real-world assessment of attenuated dosing anti-PD1 therapy as an alternative dosing strategy in a high-income country (as defined by World Bank).

The rising cost of oncological drugs poses a global challenge to patients, insurers, and policy makers, with the leading drugs worldwide by revenue from immune checkpoint inhibitors (ICIs). Despite its cost, ICI is marked as a paradigm shift, offering the potential of a long-term cure. To reduce cost, an attenuated dose of ICI based on pharmacological principles can be used while maintaining efficacy. This real-world study aims to examine the prescribing patterns, the effect of financial constraints, and the outcomes in non-small cell lung cancer (NSCLC). All patients receiving palliative intent ICI treatment for advanced NSCLC between January 2014 and April 2021 in National University Hospital, Singapore were recruited. Demographics, prescription trends, factors affecting the prescription of attenuated dose ICI (AD ICI) versus standard dose ICI (SD ICI), and the effect of dose on survival outcomes, toxicities, and costs were examined. Two hundred seventy-four received ICI. The majority of them were treated in first-line setting. One hundred sixty-two (59%) of patients received AD ICI, whereas 112 (41%) received SD ICI. Patients who did not have a supplemental private as-charged health insurance plan were more likely to have received AD ICI (OR: 4.53 [2.69-7.61] p < 0.001). There was no difference in progression-free survival (PFS) and overall survival (OS)-adjusted HR 1.07 CI [0.76, 1.50] p = 0.697 and HR 0.95 CI [0.67, 1.34] p = 0.773, respectively, between patients who received AD versus SD ICI. A cost minimization analysis evaluating the degree of cost savings related to drug costs estimated a within study cost saving of USD 7,939,059 over 7 years. Our study provides evidence for AD-ICI as a promising strategy to maximize the number of patients who can be treated with ICI. This has the potential to make significant economic impact and allow more patients to benefit from novel therapies.

Oncofetal protein IGF2BP1 regulates IQGAP3 expression to maintain stem cell potential in cancer.

We reported earlier that IQGAP3 is an important stem cell factor in rapidly proliferating isthmus stem cells in the stomach and that IQGAP3 expression is robustly induced in terminally differentiated chief cells and de-differentiated cells following tissue damage. The elevated IQGAP3 expression in cancer and its association with metastasis suggest a fundamental role for IQGAP3 in proliferating cancer stem cells. What causes IQGAP3 upregulation in cancer is unclear. Here, we show that IGF2BP1 and IQGAP3 expression levels are highest in the blastocyst, with both decreasing during adulthood. This suggests that IQGAP3, like IGF2BP1, is an early developmental gene that is aberrantly upregulated upon re-expression of IGF2BP1 during carcinogenesis. IGF2BP1 binds and stabilizes m6A-modified IQGAP3 transcripts. Downstream targets of IGF2BP1, namely SRF and FOXM1, also upregulate IQGAP3 expression. These multiple layers of IQGAP3 regulation, which may safeguard against inappropriate stem cell proliferation, present additional drug targets to inhibit IQGAP3-driven malignant growth.

Outcomes of a Phase II Study of Intraperitoneal Paclitaxel plus Systemic Capecitabine and Oxaliplatin (XELOX) for Gastric Cancer with Peritoneal Metastases.

BACKGROUND: Adding intraperitoneal paclitaxel (IP-PTX) to paclitaxel/5-fluoropyrimidine has shown promising results in patients with gastric cancer peritoneal metastases (GCPM) but has not been studied with standard-of-care platinum/fluoropyrimidine combinations. Our goal to was evaluate IP-PTX with capecitabine/oxaliplatin (XELOX) in GCPM. METHODS: Forty-four patients with GCPM received IP PTX (40 mg/m2, Days 1, 8), oral capecitabine (1000 mg/m2 twice daily, Days 1-14) and intravenous oxaliplatin (100 mg/m2, Day 1) in 21-day cycles. Patients with synchronous GCPM underwent conversion surgery if they had good response after chemotherapy, conversion to negative cytology, no extraperitoneal metastasis, and no peritoneal disease during surgery. The primary endpoint was overall survival and secondary endpoints were progression-free survival and safety. Outcomes from the trial were compared against a matched cohort of 39 GCPM patients who received systemic chemotherapy (SC) comprising platinum/fluoropyrimidine. RESULTS: The median OS for the IP and SC groups was 14.6 and 10.6 months (hazard ratio [HR] 0.44; 95% confidence interval [CI], 0.26-0.74; p = 0.002). The median PFS for the IP and SC group was 9.5 and 4.4 months respectively (HR 0.39; 95% CI 0.25-0.66; p < 0.001). Patients in the SC group were younger (IP vs. SC, 61 vs. 56 years, p = 0.021) and had better performance status (ECOG 0, IP vs. SC, 47.7% vs. 76.9%, p = 0.007) compared with the IP cohort. In IP group, conversion surgery was performed in 36.1% (13/36) of patients, with a median OS of 24.2 (95% CI 13.1-35.3) months and 1-year OS of 84.6%. CONCLUSIONS: IP PTX with XELOX is a promising treatment option for GCPM patients. In patients with good response, conversion surgery was feasible with favourable outcomes.

Systemic Treatment of Advanced Unresectable Hepatocellular Carcinoma after First-Line Therapy: Expert Recommendations from Hong Kong, Singapore, and Taiwan.

Background: Asia has a high burden of hepatocellular carcinoma (HCC) due to the high rates of chronic hepatitis B infection and accounts for 70% of HCC cases globally. In the past 20 years, the systemic treatment landscape of advanced HCC has evolved substantially - from tyrosine kinase inhibitors to immune-oncology agents plus anti-vascular endothelial growth factor agents. The appropriate sequence of therapies has become critical in optimizing patient outcomes given the increase in systemic therapeutic options. This article evaluates the evidence and provides expert recommendations for the use of systemic therapies after first-line treatment in patients with advanced HCC. Summary: Based on three virtual meetings held in early 2021, a team of 17 experts comprising oncologists, a hepatologist, and a hepatobiliary surgeon from Hong Kong, Singapore, and Taiwan reviewed available data about systemic treatments for HCC after first line and formulated 28 statements. These statements aimed to provide expert guidance on selecting first and subsequent lines of therapies as well as recommending therapies in special circumstances, such as poor liver function, posttransplantation, recent gastrointestinal bleeding, or autoimmune diseases. Data supporting the statements were drawn from clinical trials and real-world studies. The 28 statements were then evaluated anonymously using a 5-point Likert scale, and 24 reached consensus, predefined as achieving 75% agreement. Statements generated covered the selection of first-line systemic therapy, considerations and goals of second-line systemic therapies, treatment selection following first-line therapy, and treatment recommendations following first-line tyrosine kinase inhibitors, immune-oncology monotherapy, or immune-oncology combination therapy. The authors also shared expert opinion on the use of second-line systemic therapy in patients with liver dysfunction, liver transplantation, and recent gastrointestinal or autoimmune disease. Key Messages: These expert statements summarize the latest data and expert opinion on selecting systemic treatment following first-line therapy in patients with unresectable advanced or metastatic HCC.

Integration of Genomic Biology Into Therapeutic Strategies of Gastric Cancer Peritoneal Metastasis.

The peritoneum is a common site of metastasis in advanced gastric cancer (GC). Diagnostic laparoscopy is now routinely performed as part of disease staging, leading to an earlier diagnosis of synchronous peritoneal metastasis (PM). The biology of GCPM is unique and aggressive, leading to a dismal prognosis. These tumors tend to be resistant to traditional systemic therapy, and yet, this remains the current standard-of-care recommended by most international clinical guidelines. As this is an area of unmet clinical need, several translational studies and clinical trials have focused on addressing this specific disease state. Advances in genomic sequencing and molecular profiling have revealed several promising therapeutic targets and elucidated novel biology, particularly on the role of the surrounding tumor microenvironment in GCPM. Peritoneal-specific clinical trials are being designed with a combination of locoregional therapeutic strategies with systemic therapy. In this review, we summarize the new knowledge of cancer biology, advances in surgical techniques, and emergence of novel therapies as an integrated strategy emerges to address GCPM as a distinct clinical entity.

Choice of PD-L1 immunohistochemistry assay influences clinical eligibility for gastric cancer immunotherapy.

BACKGROUND: Immune checkpoint inhibitors (ICI) are now standard-of-care treatment for patients with metastatic gastric cancer (GC). To guide patient selection for ICI therapy, programmed death ligand-1 (PD-L1) biomarker expression is routinely assessed via immunohistochemistry (IHC). However, with an increasing number of approved ICIs, each paired with a different PD-L1 antibody IHC assay used in their respective landmark trials, there is an unmet clinical and logistical need for harmonization. We investigated the interchangeability between the Dako 22C3, Dako 28-8 and Ventana SP-142 assays in GC PD-L1 IHC. METHODS: In this cross-sectional study, we scored 362 GC samples for PD-L1 combined positive score (CPS), tumor proportion score (TPS) and immune cells (IC) using a multiplex immunohistochemistry/immunofluorescence technique. Samples were obtained via biopsy or resection of gastric cancer. RESULTS: The percentage of PD-L1-positive samples at clinically relevant CPS ≥ 1, ≥ 5 and ≥ 10 cut-offs for the 28-8 assay were approximately two-fold higher than that of the 22C3 (CPS ≥ 1: 70.3 vs 49.4%, p < 0.001; CPS ≥ 5: 29.1 vs 13.4%, p < 0.001; CPS ≥ 10: 13.7 vs 7.0%, p = 0.004). The mean CPS score on 28-8 assay was nearly double that of the 22C3 (6.39 ± 14.5 vs 3.46 ± 8.98, p < 0.001). At the clinically important CPS ≥ 5 cut-off, there was only moderate concordance between the 22C3 and 28-8 assays. CONCLUSION: Our findings suggest that scoring PD-L1 CPS with the 28-8 assay may result in higher PD-L1 scores and higher proportion of PD-L1 positivity compared to 22C3 and other assays. Until stronger evidence of inter-assay concordance is found, we urge caution in treating the assays as equivalent.

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.