Abstract Body (Do not enter title and authors here): Background: Malignant mesothelioma (MM) is an aggressive and rare tumor of mesothelial cells that is strongly correlated with asbestos exposure. Due to its long latency period, MM is characterized by its poor prognosis. In this study, we primarily analyzed data for the clinicopathological analysis of malignant pleural mesothelioma with comparative overall survival (OS) and cancer-specific survival (CSS) with primary pericardial mesothelioma.

Method: The data was collected from the Epidemiology and End Results (SEER) database, comprising 12,991 mesothelioma patients from 2000 to 2020.

Results: A total of 12,991 cases of MM were extracted from the database, of which 99.55% were pleural and only 0.177% were pericardial. The median age was 74 years. Regarding gender, 80% of the patients were male. MM was found to be more common in older age (>65, 77%). 52% of the patients had a tumor size greater than 5 cm. The common histologic type was mesothelioma NOS (45%), followed by the epithelioid type (36%). The most common treatment modality was chemotherapy. Multivariate analysis showed better survival outcomes in younger, female patients undergoing combination therapies. Moreover, the histologic subtype, especially epithelioid mesothelioma, showed the overall best prognosis. Regarding comparative OS and CSS between pleural and pericardial mesothelioma, the 3-year OS of pleural mesothelioma was 11.2% (95% CI: 0.107 - 0.118) and for pericardial mesothelioma, the 3-year OS was 4.7% (95% CI: 0.007 - 0.317). Pleural mesothelioma had a 1-year CSS of 37.1% (95% CI: 0.343 - 0.401), and for pericardial mesothelioma, the CSS at 9 months was 28.6% (95% CI: 0.089 - 0.922), and all patients survived < 1 year in the cohort.

Conclusion: Malignant mesothelioma is a rare and aggressive tumor. Pericardial mesothelioma has lower survival in comparison to pleural mesothelioma. Genomic analysis and including all ethnicities in future clinical trials will help in future personalized therapeutic approaches.