Prognostic impact of clinical stage on non-surgical patients with pleural mesothelioma.

Abstract

e20096 Background: Most patients with pleural mesothelioma (PM) are not surgical candidates and receive systemic therapy. Clinical stage is usually not reported in mesothelioma clinical trials. We evaluated the prognostic impact of clinical stage in mesothelioma using a large database with the hypothesis that M1 patients will have worse OS compared to M0 patients. Methods: The Surveillance, Epidemiology and End Results (SEER) Program was used to identify adult patients with PM diagnosed between 2004 and 2020, who received chemotherapy and did not undergo surgery. Patients with unknown stage were excluded. Staging was subdivided into I, II-III and IV for better accuracy. Age, sex, and stage were included in multivariable analyses (MVAs) using a Cox proportional hazard regression model. Unadjusted OS was estimated by the Kaplan-Meier method and compared using log-rank tests. Results: Among the 10,422 patients, 2,644 (25.4%) met the inclusion criteria. Histology classification was not available for 1,120 patients (42.4%), which were reported as malignant mesothelioma. Most patients were male (78.3%) and older than 70 years (54.5%). There were 970 patients (36.7%) with stage I, 893 (33.8%) with stage II-III and 781 (29.5%) with stage IV. The median OS for all patients was 11 months, with 1-year, 3-year and 5-year OS of 43.9%, 10.3% and 4.3% respectively. The median OS for stages I, II-III, and IV was 13 months, 11 months, and 9 months respectively, with 1-year OS of 50.5%, 42.8% and 36.9% respectively and 5-year OS for stages I, II-III, and IV of 5.3%, 3.0% and 4.9% respectively. The median and 1-year OS were 12 months and 46.8% respectively for M0 and 9 months and 36.9% respectively for M1 (p < 0.001). For patient with M0, the median OS for N0, N1 and N2 was 12 months, 11 months, and 11 months, respectively. In MVA, worse OS was observed in patients with age 71 or older compared to < 60 (HR 1.24, 1.09-1.4), and in male patients compared to females (HR 1.27, 1.15.-1.4). Stage IV was associated with worse OS when compared to stage II-III (HR 1.11, 1.001-1.23, p = 0.04) and stage I (HR 1.34, 1.21-1.49, p < 0.001) while stage II-III was associated with worse OS compared to stage I (HR 1.21, 1.1-1.33, p = 0.0001). Conclusions: Clinical stage is a significant predictor for outcomes in patients with unresected pleural mesothelioma treated with chemotherapy, has been underreported, and should be included in clinical trials for a better evaluation of novel treatment strategies.