166P - Impact of immunotherapy (IT) on overall survival (OS) of patients with malignant pleural mesothelioma (MPM) adjusted for tumor histology

Background

In 1^st line setting in MPM CheckMate-743 and IND227 trials demonstrated better outcomes for IT over chemotherapy in p with no-epithelioid histology. However, another trial (MAPS2, DREAM) demonstrated efficacy of IT in all tumors. The objective of this study is to evaluate the impact of IT according to histology in p with MPM.

Methods

Clinical records of MPM p treated with IT (anti-PD1/L1) were reviewed. Associations between clinical variables and outcome were assessed with multivariable time-dependent Cox regression models to adjust for immortal-time bias and histology. Survival data were calculated by the Kaplan-Meier method.

Results

Of the 228p reviewed, thirty-six p (16%) were treated with IT. Clinical characteristics of the entire cohort: median age 68 years (29-88), males: 70%, performance status (PS)1: 69%, epithelioid: 82%. Median overall survival (OS) of the entire cohort was 21.4 months (m) (CI95% 18-23.8). Epithelioid histology, PS 0, stage 1-2 and treatment with cisplatin were associated with significant improvements in OS (p<0.001). Of the 36p treated with anti-PD1/L1, 13 p received the IT in 1^st line and 19 p in 2^nd or further lines. In the multivariable time-dependent model, both histology (HR=0.51) and exposure to IT (HR=0.66) had significant impact on OS (P-values < 0.1). Patients with epithelioid tumors treated with anti-PD1/L1 at any line had median OS of 33.1 m (vs 23.8 m for p without IT), while p with non-epithelioid tumors exposed to anti-PD1/L1 had median OS of 19.5 m (vs 14.1 m without IT). In p exposed to IT in 2^nd or further lines, median OS for p with epithelioid tumors treated with IT was 24.2 m (vs 13.7 m in p without IT), and for non-epithelioid cases median OS was 6.6 m and 10.0 m for p treated with or without IT, respectively.

Conclusions

In our series of real word MPM treated with IT we did demonstrate a benefit of IT for MPM p. Considering the prognostic effect of histology and the potential immortal time bias for IT exposure, we demonstrated improved OS for p receiving IT with a trend of higher benefit in epithelioid tumors. Ongoing studies combining checkpoint inhibitors plus chemotherapy are evaluating the impact of histology in the outcomes.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.