Dual Malignancies Discovered: A Rare Case of Malignant Peritoneal Epithelioid Mesothelioma and Lung Adenocarcinoma.

Clinicians diagnosing malignant peritoneal epithelioid mesothelioma (MPM or MPeM) have historically had challenges due to the low incidence of the disease, as well as the often vague symptomatology that patients present with. Newer advances in technology, specifically in immunocytochemistry, have provided a clearer path to diagnosis. Additionally, malignant mesotheliomas must be differentiated from carcinomas. This is done via histology, immunocytochemistry, as well as a careful incorporation of the patient's clinical history. In this case, we present an asymptomatic 73-year-old non-smoker female with no past medical history of asbestos exposure. She was diagnosed with MPM following a routine abdominal hernia repair. Subsequent workup revealed a lung infiltrate that was successfully biopsied and resected, evidently found to be adenocarcinoma. A careful review of the resulting pathology, as well as the interpretation of immunocytochemistry, supported the notion that the patient had two independent malignant processes occurring at once. This case underscores the rarity of two similar, yet distinct cancers, as well as epidemiology, symptomatology, histology, immunocytochemistry, and prognosis.

High mobility group box 1 mediates inflammatory responses in malignant peritoneal mesothelioma.

BACKGROUND: Serum high mobility group box 1 (HMGB1) serves as a diagnostic biomarker for malignant peritoneal mesothelioma (MPM) patients, yet its diagnostic significance within MPM tumor tissues remains uncertain. This study aims to elucidate the roles of HMGB1 in MPM. METHODS: HMGB1 expression analysis was conducted in both tumor and adjacent non-cancerous tissues collected from MPM patients. The two-year follow-up of MPM patients commenced from the diagnosis date. Inflammatory cytokine analysis was performed on these tissues, and Pearson correlation coefficient analysis was applied to examine variable relationships. In vitro assays included constructing an HMGB1 knockdown cell line, assessing cell viability, apoptosis, and inflammatory cytokine levels to delineate HMGB1's roles in MPM. RESULTS: HMGB1 overexpression was observed in MPM tumor tissues, particularly in stages III-IV. Diagnostic implications of HMGB1 for MPM were evident, augmenting its diagnostic value. HMGB1 overexpression correlated with diminished survival rates. Positive correlations existed between inflammatory cytokines and HMGB1 in MPM tumor tissues and cell lines. Suppression of HMGB1 regulated cell growth and apoptosis in MPM cell lines. CONCLUSION: HMGB1 exhibits diagnostic potential for MPM and modulates inflammatory responses within the disease context.

Peritoneal Carcinomatosis: When Everything Is Not What It Seems.

Malignant peritoneal mesothelioma (MPM) is a rare neoplasm with a low incidence rate worldwide but high morbidity and mortality rates. Due to its rarity, the studies are scarce. We present a case of a 73-year-old woman admitted to the internal medicine unit with constitutional syndrome, abdominal pain, and ascites. Throughout the investigation, aspects suggestive of peritoneal carcinomatosis were identified. An extensive study was then carried out in an attempt to identify the primary tumor, which proved to be unsuccessful. During the two weeks of hospitalization, the patient's clinical condition worsened, with an increase in ascites and a deterioration in her general health. This case was then discussed with an oncology consultant, and it was decided to biopsy a peritoneal implant with the support of interventional radiology. MPM was then diagnosed through histopathology. With this case, the authors intend to highlight that, although rare, this diagnosis should be considered when appropriate and that even in the suspicion of secondary disease, the primary tumor should always be identified, as localized MPM may be curable.

A Complete Response to Pembrolizumab in Malignant Peritoneal Mesothelioma: A Case Report.

Malignant peritoneal mesothelioma (MPeM) is a rare cancer of the peritoneum with a poor prognosis and nonspecific clinical course. We discuss a case of MPeM in a 59-year-old male who presented with abdominal pain and distension, without any known previous asbestos exposure. The diagnosis was made after a second biopsy finally confirmed epithelioid MPeM in an advanced stage with pleural effusion. The patient underwent six cycles of chemotherapy with cisplatin and pemetrexed, experienced disease progression, and was then started on pembrolizumab as a second-line treatment. The patient achieved a complete response after two years of treatment with pembrolizumab and has been disease-free for almost four years with an Eastern Cooperative Oncology Group (ECOG) performance status of 0. Despite the lack of evidence to support the treatment with immunotherapy for MPeM, our case report encourages its use, highlighting its ability to enable a complete response with pembrolizumab with an excellent quality of life.

Risk factors and prognosis of malignant peritoneal mesothelioma with paraneoplastic syndrome.

BACKGROUND: Malignant peritoneal mesothelioma (MPM) is a rare and highly aggressive tumor. Its clinical manifestations are diverse, and the symptoms are not specific. Some patients will develop paraneoplastic syndrome (PS) during the disease course. This study aims to analyze the risk factors of PS in patients with MPM and their impacts on prognosis. METHODS: The clinical data of MPM patients who underwent cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (CRS + HIPEC) at our center from June 2015 to May 2023 were retrospectively analyzed. MPM patients were divided into PS group and non-PS group according to the diagnostic criteria. Univariate and multivariate analyses were performed to explore the risk factors of PS in MPM patients, and to analyze the impact of PS on prognosis. RESULTS: There were 146 MPM patients in this study, including 60 patients (41.1%) with PS and 86 patients (58.9%) without PS. The highest incidence of PS was thrombocytosis (33.6%), followed by neoplastic fever (9.6%). Univariate analysis revealed 8 factors (P < 0.05) with statistically significant differences between the two groups: prior surgical scores, targeted therapy history, Karnofsky performance status score, preoperative carbohydrate antigen (CA) 125 level, vascular tumor embolus, peritoneal cancer index, completeness of cytoreduction (CC) score and intraoperative ascites. Multivariate analysis identified 3 independent factors associated with PS: preoperative CA 125 level, vascular tumor embolus, and CC score. Survival analysis demonstrated that MPM patients with PS had worse prognosis, although PS was not an independent prognostic factor. CONCLUSIONS: PS is not rare in patients with MPM, and is independently associated with preoperative CA 125 level, vascular tumor embolus and CC score. PS often indicates advanced disease and poor prognosis.

Organoids derived from patients provide a new opportunity for research and individualized treatment of malignant peritoneal mesothelioma.

BACKGROUND: Malignant peritoneal mesothelioma (MPM) is an extremely rare and highly invasive tumor. Due to the lack of accurate models that reflect the biological characteristics of primary tumors, studying MPM remains challenging and is associated with an exceedingly unfavorable prognosis. This study was aimed to establish a new potential preclinical model for MPM using patient-derived MPM organoids (MPMOs) and to comprehensively evaluate the practicality of this model in medical research and its feasibility in guiding individualized patient treatment. METHODS: MPMOs were constructed using tumor tissue from MPM patients. Histopathological analysis and whole genome sequencing (WGS) were employed to determine the ability of MPMOs to replicate the original tumor's genetic and histological characteristics. The subcutaneous and orthotopic xenograft models were employed to assess the feasibility of establishing an in vivo model of MPM. MPMOs were also used to conduct drug screening and compare the results with retrospective analysis of patients after treatment, in order to evaluate the potential of MPMOs in predicting the effectiveness of drugs in MPM patients. RESULTS: We successfully established a culture method for human MPM organoids using tumor tissue from MPM patients and provided a comprehensive description of the necessary medium components for MPMOs. Pathological examination and WGS revealed that MPMOs accurately represented the histological characteristics and genomic heterogeneity of the original tumors. In terms of application, the success rate of creating subcutaneous and orthotopic xenograft models using MPMOs was 88% and 100% respectively. Drug sensitivity assays demonstrated that MPMOs have different medication responses, and these differences were compatible with the real situation of the patients. CONCLUSION: This study presents a method for generating human MPM organoids, which can serve as a valuable research tool and contribute to the advancement of MPM research. Additionally, these organoids can be utilized as a means to evaluate the effectiveness of drug treatments for MPM patients, offering a model for personalized treatment approaches.

Malignant Peritoneal Mesothelioma: An In-Depth and Up-to-Date Review of Pathogenesis, Diagnosis, Management and Future Directions.

Malignant peritoneal mesothelioma (MPM) is an extremely rare malignancy usually confined to the abdominal cavity. With an aggressive natural history, morbidity and mortality are consequences of progressive locoregional effects within the peritoneal cavity. The first reported case was in the early 20th century, however, due to the rare nature of the disease and a large gap in understanding of the clinicopathological effects, the next reported MPM cases were only published half a decade later. Since then, there has been exponential growth in our understanding of the disease, however, there are no prospective data and a paucity of literature regarding management. Traditionally, patients were treated with systemic therapy and the outcomes were very poor, with a median survival of less than one year. However, with the advent of cytoreductive surgery and locoregional chemotherapy, there have been significant improvements in survival. Even more recently, with an improved understanding of the molecular pathogenesis of MPM, there have been reports of improved outcomes with novel therapies. Given the disastrous natural history of MPM, the limited data, and the lack of universal treatment guidelines, an in-depth review of the past, present, and future of MPM is critical to improve treatment regimens and, subsequently, patient outcomes.

Brain Metastases With Malignant Peritoneal Mesothelioma: Never Reported Before.

Malignant mesothelioma is a very rare diagnosis. Malignant mesotheliomas arise from surface linings of pleura, peritoneal cavity, or tunica vaginalis and pericardium with pleural malignant mesotheliomas being the most common. The incidence of brain metastases has been very low with malignant pleural mesotheliomas, but to date, there have not been any cases reported of brain metastasis with malignant peritoneal mesotheliomas. We present a patient diagnosed with malignant peritoneal mesothelioma and was successfully treated with immunotherapy for over two years but later presented with brain metastases. Although the patient had a surgical resection followed by brain radiation, he died three months after his diagnosis of brain metastases. Immunotherapy has revolutionized the treatment of malignant mesothelioma, and patients are living longer than before. We present this patient to increase awareness of brain metastases with malignant peritoneal mesothelioma. This case also highlights that we need to investigate different treatment options for brain metastases in patients with malignant mesothelioma as conventional treatment options like surgical resection and brain radiation are not very effective.

Malignant Peritoneal Mesothelioma: A Case Report.

Malignant peritoneal mesothelioma (MPM) is a rare tumor of the serous membranes of the peritoneum and has been linked to exposure to asbestos and other risk factors. The clinical manifestations are vague, with a wide clinical spectrum, predominantly related to the abdominal involvement of the disease. Localized mesothelioma is an uncommon manifestation of the disease. Common symptoms include abdominal pain or abdominal distention, nausea, anorexia, and weight loss. Rarely, patients present with paraneoplastic syndrome. Due to the nonspecific symptoms, many patients already have advanced disease at the time of diagnosis. The authors report a case of a 75-year-old female patient who presented with symptoms of asthenia, anorexia, progressive paleness, and weight loss lasting five months. She reports later new-onset symptoms of diffuse abdominal pain and diarrhea associated with nausea. Laboratory tests showed anemia, mild leukocytosis, thrombocytosis, elevated C-reactive protein (CRP), and elevated liver enzymes. An abdominal and pelvic computed tomography (CT) scan revealed marked tissue thickening of an irregular and striated configuration of the leaflets and peritoneal reflections in an omental cake pattern, and a chest CT scan showed multiple bilateral pulmonary nodules, suggesting diffuse malignant disease. A CT-guided biopsy of a peritoneal implant was performed, establishing the diagnosis of malignant peritoneal mesothelioma. Due to rapid clinical deterioration, the patient did not receive any systemic treatment, surgery, or radiotherapy and was transitioned to comfort care. As in the presented case, most cases of MPM have diffuse peritoneal involvement at the time of diagnosis, although extra-abdominal involvement is very rare. This disease presentation is associated with high morbidity and mortality compared to cases of localized disease. There is no specific imaging diagnostic modality or valuable tumor markers for MPM. Although a CT scan remains important in the diagnostic approach, the changes found are not specific. Radiographically, MPM may present as mesenteric or parietal peritoneal nodules, visceral peritoneal thickening, ascites, or omental masses. Although these features may raise suspicion of MPM, a biopsy is necessary to confirm the diagnosis. Therefore, due to the rarity of this disease and its nonspecific signs or symptoms, MPM is difficult to diagnose, and the prognosis remains poor.

Zimberelimab plus chemotherapy as the first-line treatment of malignant peritoneal mesothelioma: A case report and review of literature.

BACKGROUND: Malignant peritoneal mesothelioma (MPeM) is a rare cancer with a poor prognosis at advanced stage, and the standard first-line treatment for inoperable patients is chemotherapy. Although combining programmed cell death 1 (PD-1) inhibitors with chemotherapy is generally considered safe and effective in several malignant solid tumors, there are few reports regarding initial immunochemotherapy in advanced MPeM. CASE SUMMARY: Here, to our knowledge, we present the first case of a patient with epithelioid subtype MPeM, who was treatment-naïve and benefited from initial PD-1 inhibitor plus standard chemotherapy with a prolonged progression-free survival (PFS) and good tolerance. A 49-year-old man was admitted to our hospital for a persistent burning sensation in the abdomen. Computed tomography revealed a solid mass in the lower abdomen, which was subsequently diagnosed histologically as epithelioid subtype MPeM by core needle biopsy. The patient received eight cycles of pemetrexed 800 mg (day 1), cisplatin 60/50 mg (day 1-2), and zimberelimab (PD-1 inhibitor) 240 mg (day 1) every 3 wk. He achieved significant reduction of peritoneal tumors with remarkable improvement in symptoms. The best tumor response was partial remission with a final PFS of 7 mo. No immune-related adverse event occurred during the combination treatment. CONCLUSION: The outcome of the present case demonstrates the promising anti-tumor activity of immunochemotherapy to treat inoperable MPeM in the future.

[Pathological classification of malignant peritoneal mesothelioma and comparative analysis with peritoneal carcinomatosis].

Objective: To analyze the pathological classification of malignant peritoneal mesothelioma (MPeM) and screen the immunohistochemical markers that can distinguish MPeM from peritoneal metastatic carcinoma (PC) . Methods: In June 2020, the pathological results of peritoneal biopsy of 158 MPeM and 138 PC patients from Cangzhou Central Hospital, Cangzhou People's Hospital, and Cangzhou Hospital of Integrated Traditional Chinese and Western Medicine from May 2011 to July 2019 were retrospectively analyzed, and the pathological classifications of MPeM in Cangzhou were summarized. Immunohistochemical markers of MPeM and PC patients were analyzed, and receiver operating characteristic curve (ROC curve) was drawn for differential diagnosis of MPeM and PC. Results: There were 55 male and 103 female MPeM patients in Cangzhou, with an average age of 57.1 years old. The asbestos exposure rate was 91.14% (144/158). The most common pathological classifications were cutaneous type, accounting for 90.51% (143/158). There were significant differences in the expression of calreticulum protein, CK5/6, vimentin, D2-40, carcinoembryonic antigen (CEA) and tail type homologous nuclear gene transcription factor 2 (CDX-2) between MPeM and PC (P<0.05). Among the 6 positive markers, the sensitivity of calreticulum protein was the highest (0.905) and CEA was the lowest (0.428) . Conclusion: Calreticulum protein, CK5/6, vimentin, D2-40, CEA and CDX-2 may be used as specific markers to distinguish the diagnosis of MPeM from PC.

Establishment of a Bayesian network model to predict the survival of malignant peritoneal mesothelioma patients after cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy.

OBJECTIVES: To establish a Bayesian network (BN) model to predict the survival of patients with malignant peritoneal mesothelioma (MPM) treated with cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC). METHODS: The clinicopathological data of 154 MPM patients treated with CRS + HIPEC at our hospital from April 2015 to November 2022 were retrospectively analyzed. They were randomly divided into two groups in a 7:3 ratio. Survival analysis was conducted on the training set and a BN model was established. The accuracy of the model was validated using a confusion matrix of the testing set. The receiver operating characteristic (ROC) curve and area under the curve were used to evaluate the overall performance of the BN model. RESULTS: Survival analysis of 107 patients (69.5%) in the training set found ten factors affecting patient prognosis: age, Karnofsky performance score, surgical history, ascites volume, peritoneal cancer index, organ resections, red blood cell transfusion, pathological types, lymphatic metastasis, and Ki-67 index (all p < 0.05). The BN model was successfully established after the above factors were included, and the BN model structure was adjusted according to previous research and clinical experience. The results of confusion matrix obtained by internal validation of 47 cases in the testing set showed that the accuracy of BN model was 72.7%, and the area under ROC was 0.74. CONCLUSIONS: The BN model was established successfully with good overall performance and can be used as a clinical decision reference.

The clinicopathological significance of TOP2A expression in malignant peritoneal mesothelioma.

BACKGROUND: Malignant peritoneal mesothelioma (MPM) is a rare malignant tumor with a high mortality rate and extremely poor prognosis. TOP2A expression is associated with cell proliferation and cell cycle progression. We aimed to demonstrate the expression profile of TOP2A in MPM and its correlation with clinicopathological features. METHODS: Clinicopathological information from 100 MPM cases was collected at Beijing Shijitan Hospital, Capital Medical University. Immunohistochemistry (IHC) was performed to evaluate TOP2A levels. The associations between TOP2A levels and clinicopathological features or prognosis were analyzed. Clinical follow-up data were reviewed to determine correlations among the pathological prognostic factors using the Kaplan-Meier estimator and univariate/multivariate Cox proportional hazards regression models. RESULTS: Among the 100 MPM patients, there were 48 males and 52 females, with a median age of 54 years (range: 24-72 years). The cutoff curve was used to find the boundary value of the TOP2A-positive rate. TOP2A positive rate ≥ 11.97 % accounted for 48 % in tumor tissue. The TOP2A-positive rate was not associated with sex, age, asbestos exposure, peritoneal carcinomatosis index (PCI) score, or completeness of cytoreduction (CC) score in MPM. Univariate analysis revealed survival-related pathological parameters, including asbestos exposure, CA125, histological type, PCI score, CC score, Ki-67 index, and TOP2A positive rate. Multivariate analysis identified that asbestos exposure history, PCI score, Ki-67 proliferation index and TOP2A positive rate in tissue are independent prognostic factors. CONCLUSIONS: High expression of TOP2A is linked to better prognosis of MPM.

Prognostic role of CD74, CD10 and Ki-67 immunohistochemical expression in patients with diffuse malignant peritoneal mesothelioma: a retrospective study.

BACKGROUND: Diagnosis and treatment of diffuse malignant peritoneal mesothelioma (DMPM) are still challenging. The aim of the present study was to explore the correlation between CD74, CD10, Ki-67 and clinicopathological parameters, and identify independent prognostic factors of DMPM. METHODS: Seventy patients with pathologically proven DMPM were retrospectively reviewed. The expression of CD74, CD10 and Ki-67 in peritoneal tissues was detected by immunohistochemical analysis using standard avidin biotin complex (ABC) immunostaining technique. Kaplan-Meier survival analysis and multivariate Cox regression analyses were performed to assess prognostic factors. The nomogram based on the Cox hazards regression model was established. C-index and calibration curve were performed to evaluate the accuracy of nomogram models. RESULTS: The median age of DMPM was 62.34 years, and the male-to-female ratio was 1: 1.80. CD74 expression was identified in 52 (74.29%) of 70 specimens, CD10 in 34 (48.57%) specimens, and higher Ki-67 in 33(47.14%) specimens. CD74 was negatively associated with asbestos exposure(r = -0.278), Ki-67(r = -0.251) and TNM stage(r = -0.313). All patients were effectively followed up in the survival analysis. Univariate analysis revealed that PCI, TNM stage, treatment, Ki-67, CD74 and ECOG PS were associated with DMPM prognosis. CD74 (HR = 0.65, 95%Cl:0.46-0.91, P = 0.014), Ki-67(HR = 2.09, 95%Cl:1.18-3.73, P = 0.012),TNM stage (HR = 1.89, 95%Cl:1.16-3.09, P = 0.011), ECOG PS(HR = 2.12, 95%Cl:1.06-4.25, P = 0.034), systemic chemotherapy (HR = 0.41, 95%Cl:0.21-0.82, P = 0.011) and intraperitoneal chemotherapy (HR = 0.34, 95%Cl:0.16-0.71, P = 0.004) were independent predictors by multivariate Cox analysis. The C­index of the nomogram for predicting overall survival (OS) was 0.81. The OS calibration curve showed good agreement between nomogram-predicted and observed survival. CONCLUSIONS: CD74, Ki-67, TNM stage, ECOG PS and treatment were independent factors affecting prognosis of DMPM. Reasonable chemotherapy treatment might improve the prognosis of patients. The proposed nomogram was a visual tool to effectively predict the OS of DMPM patients.

Recurrent malignant peritoneal mesothelioma treated by a second resection: A case report.

Key Clinical Message: Malignant peritoneal mesothelioma, a rare and poor prognosis disease, is seldom treated surgically, especially for recurrence. However, early diagnosis and aggressive treatment of primary and recurrent tumors can achieve long-term patient survival. Abstract: Malignant peritoneal mesothelioma (MPM) is a rare and aggressive tumor, and rarely indicated for surgery, especially for recurrence. In the present case, we report a rare case who could survive long-term after two surgeries in 4 years for MPM.

Morphine poisoning in a patient with malignant peritoneal mesothelioma: A case report.

Pain is one of the most common symptoms of malignant peritoneal mesothelioma. Therefore, analgesia serves an indispensable role in the treatment of this condition. Morphine is a representative opioid, which is widely used in clinical practice; however, excessive or unreasonable application can cause poisoning. Few cases of morphine poisoning have been reported, and cases of morphine poisoning in patients with malignant peritoneal mesothelioma are even more rare. Here, we present a case of morphine poisoning in a patient with malignant peritoneal mesothelioma. The patient had a high abdominal tumor load, hepatorenal insufficiency, and was treated with a combination of morphine and the sedative benzodiazepine, eventually leading to morphine poisoning. Therefore, for cancer pain, omni-directional and whole-process management should be emphasized. In patients with hepatorenal insufficiency, those treated with morphine combined with benzodiazepines, or those with a high abdominal tumor load, attention should be paid to drug absorption, excretion and interaction, and the drug dose during administration should be reduced to avoid drug poisoning. If poisoning symptoms occur, timely measures should be taken to reduce poison absorption and increase poison excretion, and antagonists should be used to reverse the poisoning and reduce the damage caused.

A case of malignant peritoneal mesothelioma with a Fitz-Hugh-Curtis syndrome-like imaging finding.

Malignant peritoneal mesothelioma (MPeM) is a rare disease with a poor prognosis that develops in the mesothelial cells of the peritoneum. We encountered a 48-year-old man with no prior asbestos exposure who visited our hospital with abdominal pain. Laboratory findings showed elevated C-reactive protein of 15.5 mg/dL. Contrast-enhanced computed tomography (CT) detected a Fitz-Hugh-Curtis syndrome-like contrast effect on the liver surface and thickening of the peritoneum. Blood culture, Mycobacterium tuberculosis-specific IFN-γ release assay, Chlamydia trachomatis and Neisseria gonorrhoeae DNA testing, and antinuclear antibody were all negative. CA125 was high at 124.8 U/mL. The laparoscopy for diagnostic purposes revealed adhesions between the liver surface and peritoneum in addition to numerous small and large white nodules on the peritoneum. Biopsy of the nodules confirmed the diagnosis of epithelial-type MPeM. Treatment was initiated with combined cisplatin and pemetrexed, and CT 6 months later showed a reduced contrast effect on the liver surface and improved peritoneal thickening. A Fitz-Hugh-Curtis syndrome-like contrast effect on the liver surface on contrast-enhanced CT may help identify MPeM.

Diagnostic and Therapeutic Pathway in Diffuse Malignant Peritoneal Mesothelioma.

Diffuse malignant peritoneal mesothelioma (DMPM) is a rare form of mesothelioma that carries a very poor prognosis. The 5-year overall survival is about 20% (±5.9). Survival is optimal for patients suitable for cytoreductive surgery (CRS) with Hyperthermic Intraperitoneal Chemotherapy (HIPEC), with a median OS ranging from 34 to 92 months. However, selecting patients for surgery remains a complex task and requires a careful preoperative workup, rational analysis of prognostic profiles, and risk prediction models. Systemic chemotherapy could be offered: (1) in the adjuvant setting for high-risk patients; (2) for patients not eligible for CRS; and (3) for those with recurrent disease. It mainly includes the combination of Platin compound with Pemetrexed or immunotherapy. The biology of DMPM is still largely unknown. However, progress has been made on some fronts, such as telomere maintenance mechanisms, deregulation of apoptosis, tyrosine kinase pathways, and mutation of BRCA1-associated protein 1 (BAP1). Future perspectives should include translational research to improve our understanding of the disease biology to identify druggable targets. We should also clear the role of immune checkpoint inhibitors and investigate new locoregional technologies, such as pressurized intraperitoneal aerosol chemotherapy (PIPAC) or normothermic intraperitoneal chemotherapy (NIPEC).

Impact of centralization of care for malignant peritoneal mesothelioma: A historical cohort study from the Dutch mesothelioma expert centers.

BACKGROUND: Malignant peritoneal mesothelioma (MPM) is a rare and aggressive cancer that has a poor prognosis. An earlier population-based study found that the majority of Dutch patients do not receive anti-cancer treatment. In 2015, Dutch Malignant Mesothelioma care was centralized in two expert centers. We reviewed treatment patterns at these centers, to assess the impact of centralization of MPM care in the Netherlands. METHODS: Data from all patients referred to the Dutch MPM expert centers from 2014 to 2020, were retrospectively collected. Descriptive statistics regarding referrals, patient and tumor characteristics, and treatment patterns were provided. Population-based incidence rates were provided by the Netherlands Cancer Registry. RESULTS: From 2014 to 2020, 78 patients were referred to the Dutch Mesothelioma expert centers, of whom 32 were female (41%). From 2014 to 2017, 27 patients were referred, whereas 51 patients were referred from 2018 to 2020. This represents about 24% and 61% of the estimated population incidence, respectively. Treatment patterns were comparable between both periods. Between 2014 and 2018, 33% of patients underwent surgery, 44% systemic therapy, and 22% received best supportive care (BSC), while this was 29%, 37%, and 33% respectively from 2018 to 2020. CONCLUSION: Centralization of care for patients with MPM resulted in an increase of annual referrals to the Dutch mesothelioma expert centers. While population-based incidence did not change during the study period, the absolute number of patients receiving treatment at our centers did increase. This might be considered a first important step towards better treatment for patients with this fatal disease.