Over the last 20 years, more modern treatment approaches, as well as changes in the clinical and pathologic features associated with malignant peritoneal mesothelioma, have contributed to the improved prognosis observed for patients with this disease, according to findings published in Modern Pathology.
Mesothelioma, a rare type of cancer associated with the serosal membranes, most commonly affects the pleura, but arises in the peritoneum in approximately 10% of cases.
Although the rarity of malignant peritoneal mesothelioma has limited its characterization, median overall survival (OS) for patients with this disease was estimated at only approximately 12 months in the period prior to the year 2000 when cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIC) were less frequently used.
Following the introduction of more modern treatment approaches, reports of median OS for these patients ranged from 31 to 92 months; nevertheless, the clinical course of the disease was observed to be highly variable. Furthermore, there is some evidence that factors inherent to the disease may be contributing to the post-2000 survival gains observed for these patients.
The aim of this study was to examine the prognostic implications of clinical and pathologic characteristics of malignant peritoneal mesothelioma in a large, multiinstitutional cohort of patients with the disease.
Of the 225 cases of patients with malignant peritoneal mesothelioma considered in this study, 39 and 186 were diagnosed with the disease prior to and following the year 2000, respectively.
A comparison of these 2 patient subgroups showed that male sex (P =.0005), older age at diagnosis (P =.01), and necrosis (P <.0001) were more common in the subgroup of patients diagnosed with malignant peritoneal mesothelioma in the pre- compared with the post-2000 era. In contrast, epithelioid histology (P <.0001) and an intermediate compared with a high level of nuclear pleomorphism (P =.024), in addition to the administration of HIC (P <.0001), were significantly more common clinical/pathologic characteristics for those patients diagnosed in the post- compared with the pre-2000 period.
Among the factors shown to be associated with longer OS on univariate analysis were post-2000 diagnosis (P =.0001), age less than 60 years at diagnosis (P =.0001), Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 (P =.01), no radiographic signs of metastasis to lymph nodes (P =.04), cytoreductive surgery (P <.0001), absence of necrosis (P =.007), treatment with HIC (P =.0001), and epithelioid histology (P <.0001).
On multivariate analysis adjusted for patient age, factors independently associated with longer OS for the overall cohort included cytoreductive surgery, non-sarcomatoid histology, and the absence of necrosis. A similar analysis performed for only those patients with disease characterized by epithelioid histology adjusted for sex, age, necrosis, nuclear pleomorphism, mitotic index, and solid architecture showed only cytoreductive surgery, lower composite nuclear grade, and tubulopapillary architecture were independently associated with OS.
“Our data emphasize that pathologic parameters have independent prognostic value, and that clinical and pathologic features cannot be assessed in isolation when caring for peritoneal mesothelioma patients,” the study authors stated.
They further noted that “given the complex interplay of clinical and pathologic factors, communication may be best facilitated by a dedicated multidisciplinary tumor board to bring together the unique combination of specialized surgeons, oncologists, radiologists, and pathologists involved in diagnosis and management of peritoneal mesothelioma patients.”
Chapel DB, Schulte JJ, Absenger G, et al. Malignant peritoneal mesothelioma: prognostic significance of clinical and pathologic parameters and validation of a nuclear-grading system in a multi-institutional series of 225 cases. Mod Pathol. Published online October 15, 2020. doi: 10.1038/s41379-020-00688-4