69: Expression of PD-L1 in Malignant Peritoneal Mesothelioma (MPM)
Friday, March 19, 2021
11:54 AM – 12:00 PM EDT
V.P. Gazivoda*, A.W. Kangas-Dick, A.A. Greenbaum, V.A. Gall, R.C. Langan, M.S. Grandhi, T.J. Kennedy, D.A. August, H.R. Alexander, Surgical Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey, UNITED STATES|C.M. Minerowicz, Pathology, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, UNITED STATES|J. Roshal, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, UNITED STATES|
Research Fellow Rutgers Cancer Institute of New Jersey New Brunswick, New Jersey, United States
Participants should be aware of the following financial/non-financial relationships:
Victor P. Gazivoda, MD: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Introduction: Recent Phase I and II studies have demonstrated anti-tumor activity in patients receiving PD-L1 blockade for malignant mesothelioma with PD-L1 expression. However, the number of patients with MPM in these studies was very small. Therefore, the frequency of PD-L1 expression and the possible role of checkpoint inhibition in MPM has not been characterized. The purpose of this study was to determine PD-L1 expression in MPM and to perform an exploratory analysis for any associations between PD-L1 expression and biological behavior in MPM.
Methods: MPM specimens were obtained from an institutional biorepository for patients undergoing cytoreductive surgery and regional and/or systemic chemotherapy from January 2018 to June 2020. Clinical data was collected retrospectively. Specimens were stained with anti-PD-L1 antibodies (Dako 22c3) according to manufacturer specifications with appropriate controls. Samples were interpreted and scored by an experienced pathologist blinded to clinical data. Scoring was performed using both tumor proportion score (TPS) or combined positive score (CPS) with a threshold of ≥ 1% representing a positive score. Cox regression analysis was performed to determine factors associated with overall survival (OS).
Results: Twenty-four total samples were obtained from 20 patients (M: 12; F: 8). Median age was 58 years (IQR 47-70). Nineteen of 24 (79%) tumor samples were CPS positive and 11/24 (46%) were TPS positive. Three patient samples had biphasic/sarcomatoid histology, known to be more aggressive, and had high CPS and TPS scores (CPS: 3, 75, 95%; TPS: 2, 60, 90%). Median OS from date of initial diagnosis was 110 months and there was no statistical difference in OS based on PD-L1 status. However, on exploratory analysis, as the CPS or TPS threshold increased, there was a trend towards shorter OS. With CPS or TPS scores >5% actuarial median OS was 49 months versus 110 months for PD-L1 scores < 5%.
Conclusion: MPM has high frequency of PD-L1 expression which may be associated with more aggressive tumor biology. These data provide the foundation for a continued evaluation of checkpoint inhibition in patients with MPM.