J Thorac Oncol. 2021 Oct 11. pii: S1556-0864(21)03215-9. [Epub ahead of print]
Michael Offin,
Soo-Ryum Yang,
Jacklynn Egger,
Gowtham Jayakumaran,
Rowanne S Spencer,
Jessica Lopardo,
Garrett M Nash,
Andrea Cercek,
William D Travis,
Mark G Kris,
Marc Ladanyi,
Jennifer L Sauter,
Marjorie G Zauderer.
BACKGROUND: Malignant peritoneal mesothelioma (MPeM) is clinically distinct and less studied than malignant pleural mesothelioma. We report the genomic and immunophenotypic features of a prospectively collected MPeM cohort.
METHODS: Next-generation sequencing (NGS) was performed on MPeM tumors. Genomic near-haploidization (GNH) was assessed. WT1, BAP1, mesothelin, VISTA, and PD-L1 were examined by immunohistochemistry (IHC) when tissue was available. Overall survival (OS) was stratified by selected genomic and IHC features.
RESULTS: Fifty consented patients with MPeM (45 epithelioid, 5 non-epithelioid) demonstrated common alterations in BAP1 (60%; 30/50), NF2 (24%; 12/50) SETD2 (22%; 11/50), and TP53 (16%; 8/50). Seventy-six percent (38/50) of specimens were evaluable for allele-specific copy number analysis; 8% (3/38) had GNH. IHC positivity rates were 93% (37/40) for mesothelin, 96% (46/48) for WT1, 50% (19/38) for PD-L1 and 89% (34/38) for VISTA. BAP1 loss by IHC was observed in 76% (29/38), including five wildtype on NGS. Combining NGS and IHC for BAP1, OS was worse with alteration/loss compared to wildtype/retained in all patients (n=37 vs. 13, 43.8 vs. 117.3 months; p=0.04) Three of thirty patients had a pathogenic germline variant: POT1 I78T, MUTYH R109Y, BAP1 E402*.
CONCLUSION: MPeM has a distinct biology and genomic composition. CDKN2A/B alterations were rare in MPeM while BAP1, NF2, TP53, SETD2, LATS2 were common. BAP1 alteration/loss was associated with shorter survival when all patients were included. A notable minority of specimens had GNH associated with NF2, TP53, and SETDB1 mutations. Pathogenic germline mutations were found in 3 of 30 patients.