Prolonged Survival is Possible in Mesothelioma Patients Managed Non-Operatively: A National Cancer Database Analysis

P. L. Zhan¹, M. E. Canavan¹, D. Boffa², G. A.. Woodard^3
1Yale university, New Haven, Connecticut ²Yale University School of Medicine, New Haven, Connecticut ³Yale School of Medicine, New Haven, Connecticut

Purpose: Durable long-term survival in malignant pleural mesothelioma has historically been associated with surgical resection. In light of recently-published MARS 2 randomized trial data demonstrating no benefit to cytoreductive surgical resection over non-surgical management in resectable pleural mesothelioma, we explored whether long-term survival could be achieved without surgery.

Methods: The National Cancer Database (NCDB) was queried for all adult patients diagnosed with malignant pleural mesothelioma between 2010 and 2016. The characteristics of patients who survived 5 years or more after diagnosis and those who survived less than 5 years after diagnosis were assessed. Five-year overall survival (OS) was calculated for 1) patients who received chemotherapy only; 2) patients who received both chemotherapy and surgery; and 3) the special subset of patients who received chemotherapy but had refused or not received a recommended surgery. Adjusted survival analysis was performed using Kaplan-Meier analysis among patients who were propensity score matched using demographic, tumor, facility, and baseline health characteristics.

Results: In the NCDB,16,916 adult patients were diagnosed with mesothelioma between 2010 and 2016, including 9.4% (1,589) who survived ≥5 years after diagnosis. The five-year survivors included 943 patients who received surgery, as well as 554 patients who did not receive any surgical intervention. Among patients who did not undergo surgery, patients who lived more than 5 years were more likely to be younger, female, privately insured, and had fewer comorbidities than those who lived less than 5 years. They were also more likely to have epithelioid and lower clinical stage tumors and be treated with chemotherapy. Five-year OS was 5.7% for patients who received chemotherapy only (n=4,938; median OS 11.5 months), compared with 23.7% for patients who received both chemotherapy and surgery (n=2,333; median OS 24.5 months).

Historically, critics of surgical management have attributed favorable surgical outcomes to patient selection. Interestingly, the subset of non-surgically managed patients who were actually recommended to have surgery, but elected to be treated non-operatively, experienced a better outcome (n=82); 5-year OS was 15.9% (median OS 22.8 months). After matching these patients to those who received chemotherapy and underwent surgery, there was no statistically significant difference in 5-year OS (median OS 22.5 months).

Conclusion: Real-world data from the NCDB are comparable to the 5-year OS rates observed in MARS 2, demonstrating that long-term survival is possible for some patients without surgical resection. Nearly 16% of patients who were treated with chemotherapy and did not undergo a recommended surgery lived for 5 years or more after diagnosis. Methods to identify mesothelioma patients who are most likely to experience long-term survival based on patient characteristics or disease biology are needed to better inform prognosis and help guide treatment recommendations.

Identify the source of the funding for this research project: N/A