Omics analyses in peritoneal metastasis-utility in the management of peritoneal metastases from colorectal cancer and pseudomyxoma peritonei: a narrative review

Precision Oncology and Systemic Targeted Therapy in Pseudomyxoma Peritonei

PURPOSE

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.

EXPERIMENTAL DESIGN

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.

RESULTS

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.

CONCLUSIONS

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.

Novel drug resistance mechanisms and drug targets in BRAF-mutated peritoneal metastasis from colorectal cancer

BACKGROUND

Patients with peritoneal metastasis from colorectal cancer (PM-CRC) have inferior prognosis and respond particularly poorly to chemotherapy. This study aims to identify the molecular explanation for the observed clinical behavior and suggest novel treatment strategies in PM-CRC.

METHODS

Tumor samples (230) from a Norwegian national cohort undergoing surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) with mitomycin C (MMC) for PM-CRC were subjected to targeted DNA sequencing, and associations with clinical data were analyzed. mRNA sequencing was conducted on a subset of 30 samples to compare gene expression in tumors harboring BRAF or KRAS mutations and wild-type tumors.

RESULTS

BRAF mutations were detected in 27% of the patients, and the BRAF-mutated subgroup had inferior overall survival compared to wild-type cases (median 16 vs 36 months, respectively, p < 0.001). BRAF mutations were associated with RNF43/RSPO aberrations and low expression of negative Wnt regulators (ligand-dependent Wnt activation). Furthermore, BRAF mutations were associated with gene expression changes in transport solute carrier proteins (specifically SLC7A6) and drug metabolism enzymes (CES1 and CYP3A4) that could influence the efficacy of MMC and irinotecan, respectively. BRAF-mutated tumors additionally exhibited increased expression of members of the novel butyrophilin subfamily of immune checkpoint molecules (BTN1A1 and BTNL9).

CONCLUSIONS

BRAF mutations were frequently detected and were associated with particularly poor survival in this cohort, possibly related to ligand-dependent Wnt activation and altered drug transport and metabolism that could confer resistance to MMC and irinotecan. Drugs that target ligand-dependent Wnt activation or the BTN immune checkpoints could represent two novel therapy approaches.

Breaking the Mucin Barrier: A New Affinity Chromatography-Mass Spectrometry Approach to Unveil Potential Cell Markers and Pathways Altered in Pseudomyxoma Peritonei

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare peritoneal mucinous carcinomatosis with largely unknown underlying molecular mechanisms. Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy is the only therapeutic option; however, despite its use, recurrence with a fatal outcome is common. The lack of molecular characterisation of PMP and other mucinous tumours is mainly due to the physicochemical properties of mucin.

RESULTS

This manuscript describes the first protocol capable of breaking the mucin barrier and isolating proteins from mucinous tumours. Briefly, mucinous tumour samples were homogenised and subjected to liquid chromatography using two specific columns to reduce mainly glycoproteins, albumins and immunoglobulin G. The protein fractions were then subjected to mass spectrometry analysis and the proteomic profile obtained was analysed using various bioinformatic tools. Thus, we present here the first proteome analysed in PMP and identified a distinct mucin isoform profile in soft compared to hard mucin tumour tissues as well as key biological processes/pathways altered in mucinous tumours. Importantly, this protocol also allowed us to identify MUC13 as a potential tumour cell marker in PMP.

CONCLUSIONS

In sum, our results demonstrate that this protein isolation protocol from mucin will have a high impact, allowing the oncology research community to more rapidly advance in the knowledge of PMP and other mucinous neoplasms, as well as develop new and effective therapeutic strategies.

Genomic Characterization and Clinical Outcomes of Patients with Peritoneal Metastases from the AACR GENIE Biopharma Collaborative Colorectal Cancer Registry

Peritoneal metastases (PM) are common in metastatic colorectal cancer (mCRC). We aimed to characterize patients with mCRC and PM from a clinical and molecular perspective using the American Association of Cancer Research Genomics Evidence Neoplasia Information Exchange (GENIE) Biopharma Collaborative (BPC) registry. Patients' tumor samples underwent targeted next-generation sequencing. Clinical characteristics and treatment outcomes were collected retrospectively. Overall survival (OS) from advanced disease and progression-free survival (PFS) from start of cancer-directed drug regimen were estimated and adjusted for the left truncation bias. A total of 1,281 patients were analyzed, 244 (19%) had PM at time of advanced disease. PM were associated with female sex [OR: 1.67; 95% confidence interval (CI): 1.11-2.54; P = 0.014] and higher histologic grade (OR: 1.72; 95% CI: 1.08-2.71; P = 0.022), while rectal primary tumors were less frequent in patients with PM (OR: 0.51; 95% CI: 0.29-0.88; P < 0.001). APC occurred less frequently in patients with PM (N = 151, 64% vs. N = 788, 79%) while MED12 alterations occurred more frequently in patients with PM (N = 20, 10% vs. N = 32, 4%); differences in MED12 were not significant when restricting to oncogenic and likely oncogenic variants according to OncoKB. Patients with PM had worse OS (HR: 1.45; 95% CI: 1.16-1.81) after adjustment for independently significant clinical and genomic predictors. PFS from initiation of first-line treatment did not differ by presence of PM. In conclusion, PM were more frequent in females and right-sided primary tumors. Differences in frequencies of MED12 and APC alterations were identified between patients with and without PM. PM were associated with shorter OS but not with PFS from first-line treatment.

SIGNIFICANCE

Utilizing the GENIE BPC registry, this study found that PM in patients with colorectal cancer occur more frequently in females and right-sided primary tumors and are associated with worse OS. In addition, we found a lower frequency of APC alterations and a higher frequency in MED12 alterations in patients with PM.

Whole-Exome Sequencing Identifies Mutation Profile and Mutation Signature-Based Clustering Associated with Prognosis in Appendiceal Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a rare malignant clinical syndrome with little known about the global mutation profile. In this study, whole-exome sequencing (WES) was performed in 49 appendiceal PMP to investigate mutation profiles and mutation signatures. A total of 4,020 somatic mutations were detected, with a median mutation number of 56 (1-402). Tumor mutation burden (TMB) was generally low (median 1.55 mutations/Mb, 0.12-11.26 mutations/Mb). Mutations were mainly enriched in the function of cancer-related axonogenesis, extracellular matrix-related processes, calcium signaling pathway, and cAMP signaling pathway. Mutations in FCGBP, RBFOX1, SPEG, RTK-RAS, PI3K-AKT, and focal adhesion pathways were associated with high-grade mucinous carcinoma peritonei. These findings revealed distinct mutation profile in appendiceal PMP. Ten mutation signatures were identified, dividing patients into mutation signature cluster (MSC) 1 (N = 28, 57.1%) and MSC 2 (N = 21, 42.9%) groups. MSC (P = 0.007) was one of the four independent factors associated with 3-year survival. TMB (P = 0.003) and microsatellite instability (P = 0.002) were independent factors associated with MSC 2 grouping. Taken together, our findings provided a broader view in the understanding of molecular pathologic mechanism in appendiceal PMP and may be critical to developing an individualized approach to appendiceal PMP treatment.

IMPLICATIONS

This work describes exhaustive mutation profile of PMP based on WES data and derives ten mutation signatures, which divides patients into two clusters and serve as an independent prognostic factor associated with 3-year survival.

Antitumor effect of a small-molecule inhibitor of KRASG12D in xenograft models of mucinous appendicular neoplasms

Pseudomyxoma peritonei (PMP) is a rare disease characterized by a massive accumulation of mucus in the peritoneal cavity. The only effective treatment is aggressive surgery, aimed at removing all visible tumors. However, a high percentage of patients relapse, with subsequent progression and death. Recently, there has been an increase in therapies that target mutated oncogenic proteins. In this sense, KRAS has been reported to be highly mutated in PMP, with KRASG12D being the most common subtype. Here, we tested the efficacy of a small-molecule KRASG12D inhibitor, MRTX1133, in a high-grade PMP xenograft mouse model carrying a KRASG12D mutation. The results obtained in this work showed a profound inhibition of tumor growth, which was associated with a reduction in cell proliferation, an increase in apoptosis, and a reduction in the MAPK and PI3K/AKT/mTOR signaling pathways. In conclusion, these results demonstrate the high potency and efficacy of MRTX1133 in KRASG12D-PMP tumors and provide a rationale for clinical trials.

Identification of Hub Genes Associated with Gastric Cancer via Bioinformatics Analysis and Validation Studies

Introduction

Hub genes related to the development of gastric cancer (GC) were identified based on bioinformatics methods. This study aimed to identify GC hub genes, explore the expression of genes in GC and their correlation with prognosis, so as to provide strategies for GC diagnosis and targeted therapy.

Methods

Two messenger RNA (mRNA) microarray datasets were downloaded from GEO database. These data were combined with TCGA database to obtain common DEGs between GC tissues and normal tissues. GO and KEGG pathway enrichment analysis was performed. Visualized PPI network analysis was performed by Cytoscape to further identify hub genes. GEPIA database was used to evaluate the prognostic value of hub genes. The online software Ualcan was applied to analyze the expression of the prognosis-related genes in cancer tissues and normal tissues from different perspectives of primary GC, TNM stage, nodal metastasis status and tumor grade. Immunohistochemical staining of GC tissues and normal tissues was performed to evaluate the expression of signature genes in GC.

Results

Eighty-four common differentially expressed genes (DEGs) in GC were identified. These genes were closely related to the P13K-Akt signal pathway and other signaling pathways. Ten hub genes were identified. Collagen type I alpha 1 (COL1A1) and collagen type IV alpha 1 (COL4A1) were significantly associated with poor prognosis of GC and were all positively correlated with T stage, distant metastasis, and TNM stage of GC. Immunohistochemistry revealed that the expression of these 2 genes was upregulated in GC tissues. These 2 genes expression was negatively related with 5-year survival rate of GC patients.

Conclusion

Ten highly expressed hub genes in GC tissue were mined by bioinformatics method. COL1A1 and COL4A1 were significantly associated with the prognosis of GC. This study provided a theoretical basis for the pathogenesis, clinical diagnosis and therapeutic targets of GC.

External multicentre validation of pseudomyxoma peritonei PSOGI-Ki67 classification

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare malignant disease. Adding of the Ki67 proliferation index to the PSOGI PMP classification provided two different subcategories of the extensive HG-PMP group (HG-PMP ≤15% and HG-PMP >15%) with different survival in a previous unicentric study. This study aims to carry out an external and multicentre validation of this new proposed classification.

METHOD

It was a prospective analysis of samples from a historical and international cohort of patients. A representative area with higher cellular density was used to determine the Ki67%. The Ki67 proliferation index (%) was determined in all the HG-PMP patients. A Cox proportional hazard models and multivariable COX models were used. The Kaplan-Meier method and the two-tailed log-rank test were used to analyse the effect of different PSOGI-Ki67 categories on OS and DFS. Its predictive accuracy was analysed using Harrel's C-index and the ROC curve. The calibration was performed using the calibration plots matching.

RESULTS

After exclusions, 349 patients were available for analysis. The 5-years OS were 86% for LG-PMP, 59% for HG-PMP≤15, 38% for HG-PMP>15 and 42% for SRC-PMP (p = 0.0001). The 5-years DFS were 49% for LG-PMP, 35% for HG-PMP≤15, 16% for HG-PMP>15 and 18% SRC-PMP (p = 0.0001). The discrimination capability of PSOGI-Ki67 was validated.

CONCLUSION

the PSOGI-Ki67 classification discriminates and predicts the OS and DFS in patients with PMP dividing the HG-PMP category into two well-defined sub-categories. The Ki67 proliferation index should be incorporated routinely in the pathology report for these patients.

Genetic alterations in peritoneal metastatic tumors predicted the outcomes for hyperthermic intraperitoneal chemotherapy

Introduction

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are considered for patients with peritoneal metastasis (PM). However, patients selection that relies on conventional prognostic factors is not yet optimal. In this study, we performed whole exome sequencing (WES) to establish tumor molecular characteristics and expect to identify prognosis profiles for PM management.

Methods

In this study, blood and tumor samples were collected from patients with PM before HIPEC. Tumor molecular signatures were determined using WES. Patient cohort was divided into responders and non-responders according to 12-month progression-free survival (PFS). Genomic characteristics between the two cohorts were compared to study potential targets.

Results

In total, 15 patients with PM were enrolled in this study. Driver genes and enriched pathways were identified from WES results. AGAP5 mutation was found in all responders. This mutation was significantly associated with better OS (p = 0.00652).

Conclusions

We identified prognostic markers that might be useful to facilitate decision-making before CRS/HIPEC.

The molecular biology of peritoneal metastatic disease

Peritoneal metastases are a common form of tumor cell dissemination in gastrointestinal malignancies. Peritoneal metastatic disease (PMD) is associated with severe morbidity and resistance to currently employed therapies. Given the distinct route of dissemination compared with distant organ metastases, and the unique microenvironment of the peritoneal cavity, specific tumor cell characteristics are needed for the development of PMD. In this review, we provide an overview of the known histopathological, genomic, and transcriptomic features of PMD. We find that cancers representing the mesenchymal subtype are strongly associated with PMD in various malignancies. Furthermore, we discuss the peritoneal niche in which the metastatic cancer cells reside, including the critical role of the peritoneal immune system. Altogether, we show that PMD should be regarded as a distinct disease entity, that requires tailored treatment strategies.

Intraoperative oxygen tension and redox homeostasis in Pseudomyxoma peritonei: A short case series

Introduction

Pseudomyxoma peritonei (PMP) is a rare malignant disease characterized by a massive multifocal accumulation of mucin within the peritoneal cavity. The current treatment option is based on complete cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy. However, the recurrence is frequent with subsequent progression and death. To date, most of the studies published in PMP are related to histological and genomic analyses. Thus, the need for further studies unveiling the underlying PMP molecular mechanisms is urgent. In this regard, hypoxia and oxidative stress have been extensively related to tumoral pathologies, although their contribution to PMP has not been elucidated.

Methods

In this manuscript, we have evaluated, for the first time, the intratumoral real-time oxygen microtension (pO2mt) in the tumor (soft and hard mucin) and surrounding healthy tissue from five PMP patients during surgery. In addition, we measured hypoxia (Hypoxia Inducible Factor-1a; HIF-1α) and oxidative stress (catalase; CAT) markers in soft and hard mucin from the same five PMP patient samples and in five control samples.

Results

The results showed low intratumoral oxygen levels, which were associated with increased HIF-1α protein levels, suggesting the presence of a hypoxic environment in these tumors. We also found a significant reduction in CAT activity levels in soft and hard mucin compared with healthy tissue samples.

Discussion

In conclusion, our study provides the first evidence of low intratumoral oxygen levels in PMP patients associated with hypoxia and oxidative stress markers. However, further investigation is required to understand the potential role of oxidative stress in PMP in order to find new therapeutic strategies.

Serum and ascites tumor markers in the diagnostic and prognostic prediction for appendiceal pseudomyxoma peritonei

BACKGROUND

To investigate the expression of carcinoembryonic antigen (CEA), cancer antigen 199 (CA199) and CA125 in serum and ascites of appendiceal pseudomyxoma peritonei (PMP) patients relative to their diagnostic and predictive value.

METHODS

The study comprised 183 patients with pathologically confirmed appendiceal PMP, enrolled from May 2012 to June 2020, in Aerospace Center Hospital. Serum and ascites tumor markers were obtained, and their diagnostic values were compared by receiver operating characteristic (ROC) curves. The prognostic factors of appendiceal PMP with different pathologic subgroups were calculated by univariate and multivariate Cox proportional hazard regression models.

RESULTS

There were significant differences between the numbers of patients with positive CEA and CA199 in serum vs. ascites: p = 0.034 in CEA and p = 0.006 in CA199, respectively. The sensitivities with optimal cut-off values for ascites markers of CEA, CA199 and CA125 were 83.5%, 88.9% and 72.6%, respectively. CEA in ascites showed significant difference in the diagnosis of appendiceal PMP (p = 0.000); the areas under the ROC curves (AUROCs) and specificity were 0.725, 70.7%, respectively. Univariate analysis showed that the higher the ascites tumor markers, the poorer the survival (p = 0.014). Multivariate analysis indicated that completeness of cytoreduction (CCR), ascites CEA and pathological grade were independent risk factors for overall survival (OS).

CONCLUSION

CEA in ascites can be used to help specify the origin of PMP. Furthermore, elevation of ascites CEA, high pathological grade and incomplete cytoreduction predicted poor prognosis of appendiceal PMP.

Molecular Analyses in Peritoneal Metastasis from Colorectal Cancer: A Review-An English Version

Despite a trend showing continued improvement in survival by combing targeted agents in colorectal cancer, the improvement was limited, and clinically meaningful benefits were not achieved in peritoneal metastasis. The role of cytoreductive surgery (CRS) and proportion of the benefit from hyperthermic intraperitoneal chemotherapy (HIPEC) have been questioned. The PRODIGE 7 study aimed to assess the specific contribution of HIPEC to the survival benefit of peritoneal metastasis from colorectal cancer (CRC-PM) by grouping CRS alone versus CRS with oxaliplatin-based HIPEC, but failed to show any survival improvement. Of these criticisms, oxaliplatin resistance was suggested as the main cause of the negative result. In this regard, the relative resistance to oxaliplatin in consensus molecular subtype 4 colorectal cancer (CRC) is of great interest. Recent treatments for metastatic CRC have gradually moved to precision medicine based on individual biological information through high-throughput technology such as next generation sequencing. This review aimed to provide an overview of the current status of studies reporting the molecular knowledge of CRC-PM.

Molecular analyses of peritoneal metastasis from colorectal cancer

Background: Despite a trend showing continued improvement in survival by combing targeted agents for colorectal cancer (CRC), the improvement observed is limited. Moreover, clinically relevant benefits were not achieved in peritoneal metastasis cases. The role of cytoreductive surgery (CRS) and the benefits of hyperthermic intraperitoneal chemotherapy (HIPEC) have been questioned. This review aimed to provide an overview of the current status of the studies reporting on the molecular knowledge of peritoneal metastasis from CRC (CRC-PM).Current Concepts: The PRODIGE 7 study was performed to assess the specific contributions of HIPEC to the survival benefit in CRC-PM cases by comparing CRS treatment alone and CRS with oxaliplatin-based HIPEC. However, this study did not reveal any survival improvement, and oxaliplatin resistance was suggested as the main cause of this negative outcome. Hence, the relative resistance to oxaliplatin in consensus molecular subtype (CMS) 4 CRC is of great interest.Discussion and Conclusion: Recent treatments for metastatic CRC have gradually moved to precision medicine based on individual biological information through high-throughput technology, such as next-generation sequencing. In the transcriptome study, CRC-PM was identified as an almost homogeneous CMS4 classification, which is known to have strong resistance to oxaliplatin-based chemotherapy. These results suggest the need to clarify complex sub-signal transmission pathways derived from transcriptome or proteome studies of CRC-PM. Finally, to compare two studies, it is necessary to establish a representative patient group and consider standardized sample collection, treatment, and analysis.

Effects of GLP-1 Receptor Agonists on Biological Behavior of Colorectal Cancer Cells by Regulating PI3K/AKT/mTOR Signaling Pathway

Colorectal cancer (CRC) has become one of the top ten malignant tumors with a high incidence rate and mortality. Due to the lack of a good CRC screening program, most of the CRC patients are being transferred at the time of treatment. The conventional treatment cannot effectively improve the prognosis of CRC patients, and the target drugs can significantly prolong the overall survival of patients in the advanced stage. However, the use of single drug may lead to acquired drug resistance and various serious complications. Therefore, combined targeted drug therapy is the main alternative treatment with poor effect of single targeted drug therapy, which has important research significance for the treatment of CRC. Therefore, this study intends to culture CRC cell lines in vitro at the cell level and intervene with the GLP-1 receptor agonist liraglutide. The effects of liraglutide on the PI3K/Akt/mTOR signal pathway and CRC cell proliferation, cycle, migration, invasion, and apoptosis are explored by detecting cell proliferation, cycle, migration, invasion, and apoptosis and the expression of related mRNA and protein. The results showed that liraglutide, a GLP-1 receptor agonist, could block the CRC cell cycle, reduce cell proliferation, migration, and invasion and promote apoptosis by inhibiting the PI3K/Akt/mTOR signal pathway.

Peptide vaccine targeting mutated GNAS: a potential novel treatment for pseudomyxoma peritonei

Background

Pseudomyxoma peritonei (PMP) is a rare, slow-growing abdominal cancer with no efficacious treatment options in non-resectable and recurrent cases. Otherwise, rare activating mutations in the GNAS oncogene are remarkably frequent in PMP and the mutated gene product, guanine nucleotide-binding protein α subunit (Gsα), is a potential tumor neoantigen, presenting an opportunity for targeting by a therapeutic cancer vaccine.

Methods

Tumor and blood samples were collected from 25 patients undergoing surgery for PMP (NCT02073500). GNAS mutation analysis was performed by next-generation targeted sequencing or digital droplet PCR. Responses to stimulation with Gsα mutated (point mutations R201H and R201C) 30 mer peptides were analyzed in peripheral blood T cells derived from patients with PMP and healthy donors. Fresh PMP tumor samples were analyzed by mass cytometry using a panel of 35 extracellular markers, and cellular subpopulations were clustered and visualized using the visual stochastic network embedding analysis tool.

Results

GNAS mutations were detected in 22/25 tumor samples (88%; R201H and R201C mutations detected in 16 and 6 cases, respectively). Strong T cell proliferation against Gsα mutated peptides was observed in 18/24 patients with PMP. Mass cytometry analysis of tumor revealed infiltration of CD3 +T cells in most samples, with variable CD4+:CD8 + ratios. A large proportion of T cells expressed immune checkpoint molecules, in particular programmed death receptor-1 and T cell immunoreceptor with Ig and ITIM, indicating that these T cells were antigen experienced.

Conclusion

These findings point to the existence of a pre-existing immunity in patients with PMP towards mutated Gsα, which has been insufficient to control tumor growth, possibly because of inhibition of antitumor T cells by upregulation of immune checkpoint molecules. The results form a rationale for exploring peptide vaccination with Gsα peptides in combination with immune checkpoint inhibiton as a possible curative treatment for PMP and other GNAS mutated cancers.

A Proposal for Modification of the PSOGI Classification According to the Ki-67 Proliferation Index in Pseudomyxoma Peritonei

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare malignancy, classified according to the Peritoneal Surface Oncology Group International (PSOGI) classification, whose response to treatment remains highly heterogeneous within the high-grade (HG) category. Molecular profiling of PMP cases might help to better categorize patients and predict treatment responses.

METHODS

We studied the Ki-67 proliferation rate and P53 overexpression in tissue samples from our historical cohort of HG-PMP patients. We established as cut-off levels the third quartile of each marker to perform univariate and multivariate Cox regression survival analyses. According to these results, the HG-PMP category was divided into subcategories and a new survival analysis was performed.

RESULTS

A total of 90/117 patients with PMP undergoing cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) were selected for secondary analysis. The survival analysis of the HG-PMP category for preoperative variables showed that a proliferation index defined by Ki-67 >15% is a bad prognostic factor, with a hazard ratio (HR) of 3.20 (95% confidence interval [CI] 1.24-8.25). Accordingly, the HG-PMP group was divided using the Ki-67 15% cut-off. The new PSOGI/Ki-67 variable was an independent prognostic factor for overall survival (OS), with an HR of 3.74 (95% CI 1.88-7.47), and disease-free survival (DFS), with an HR of 4.184 (95% CI 1.79-9.75). The estimated 5-year OS rate was 100%, 70% and 24% for the LG-PMP, HG-PMP ≤15% and HG-PMP >15% groups, respectively (p = 0.0001), while the 5-year DFS rate was 90%, 44% and 0%, respectively (p = 0.0001).

CONCLUSION

Division of the HG-PMP category of the PSOGI classification, according to the Ki-67 proliferation index, provides two well-defined subcategories, with significant differences in terms of OS and DFS, and hence high prognostic value.