Immediate Versus Deferred Systemic Therapy in Patients With Mesothelioma

The 2018 ASCO pleural mesothelioma (PM) treatment guideline states that "a trial of expectant observation may be offered" in patients with asymptomatic inoperable epithelioid mesothelioma with low disease burden. The aim of our analysis was to evaluate clinical characteristics and outcomes in PM-patients managed with initial observation and deferred treatment initiation.

We retrospectively collected clinicodemograhic and outcome data of patients with inoperable PM. Patients were assigned to 2 treatment decision groups: decision to start immediate systemic treatment (Immediate Treatment Group) versus observation and deferring treatment (Deferred Treatment group).

Of 222 patients with advanced PM, systemic treatment was started immediately in the majority of patients (189, 85%; immediate group); treatment was deferred in 33 (15%) patients (deferred group); systemic therapy was chemotherapy-based in 91% and 79% respectively. Patients in the deferred group were older (70 vs 67 years, p = .05), less likely to have stage IV disease (28% vs. 51%, p = .08) and more often had epithelioid histology (90% vs. 70%, p = .03). Nineteen patients (58%) in the deferred group eventually received treatment. With a median follow-up time of 10.9 months median overall survival (OS) in the entire cohort was 12.4 months and was significantly longer in the deferred group (20.6 months vs. 11.5 months, p = .02). No difference in median progression-free survival (PFS) in first-line treatment between groups was seen (5.4 and 5.3 months).

This real-world analysis suggests that deferral of systemic therapy and close observation may not impact OS or physician-assessed PFS in selected PM-patients.