Incidence, Survival Analysis and Future Perspective of Primary Peritoneal Mesothelioma (PPM): A Population-Based Study from SEER Database.

Background: Primary peritoneal mesothelioma (PPM) is a rare and aggressive tumor arising from the visceral and parietal peritoneum. The diagnosis and treatment of PPM are often delayed because of non-specific clinical presentation, and the prognosis is worse. The current study investigated the demographic, clinical, and pathological factors affecting patient prognosis and survival in PPM.

Methods: Demographic and clinical data of 1998 patients with PPM were extracted from the Surveillance Epidemiology and End Results (SEER) database (1975-2016). The chi-square test, paired -test, and multivariate analysis were used to analyze the data.

Results: The majority of PPM patients were male (56.2%, < 0.005) and Caucasian (90.4%, < 0.005, with a mean age of diagnosis was 69 ± 13 years. The grading, histological, and tumor size information were classified as "Unknown" in most of the cases, but when available, poorly differentiated tumors (8.7%), malignant mesothelioma, not otherwise specified (63.4%) and tumors > 4 cm in size (8%), respectively, were most common, < 0.005. Chemotherapy was administered to 50.6% of patients, followed by resection (29.2%) and radiation (1.5%), < 0.001. The cohort of PPM had a five-year overall survival of 20.3% (±1.1), compared to 43.5% (±5.9), 25.9% (± 8.4), and 18.7% (±1.6) for those with surgery, radiation, or chemotherapy alone, respectively. Poor differentiation (OR = 4.2, CI = 3.3-4.9), tumor size > 4 cm (OR = 3.9, CI = 3.2-4.5), Caucasian race (OR = 2.9, CI = 2.6-4.4), and distant SEER stage (OR = 2.5, CI = 1.1-3.2) were all linked with increased mortality ( < 0.001).

Conclusion: An extremely rare and aggressive peritoneal tumor, PPM may be difficult to identify at the time of diagnosis. Radiation therapy likely to have a limited function in the treatment of this condition, with surgery and chemotherapy being the primary choices. All PPM patients should be enrolled in a nationwide registry to improve our understanding of the pathogenesis and identify factors affecting survival.