MGMT methylation in metastatic pancreatic cancer (mPAC): A single center experience

Background Metastatic pancreatic cancer (mPAC) is a devastating disease with few therapeutic options. O6-methylguanine-DNA methyltransferase (MGMT) is a key DNA repair gene and there are reports of MGMT alterations in various gastrointestinal cancers, including colorectal cancer and mPAC. Low MGMT expression by immunohistochemistry (IHC) and MGMT promoter methylation ultimately result in diminished DNA-repair of O6-alkylguanine adducts and enhanced sensitivity to alkylating agents, such as temozolomide (TMZ). This report presents data on MGMT testing mPAC pts admitted at our center. Methods Formalin-fixed paraffin-embedded (FFPE) tissue samples were examined via methyl specific PCR (EZ DNA Methylation-Gold™ KIT), to assess MGMT promoter methylation, and IHC, to assess protein expression. Furthermore, Next Generation Sequencing (50 genes “Hotspot Cancer Panel, Ion Torrent®” and “Oncomine BRCA Research Assay”) and PCR analysis of microsatellite instability (MSI) were performed. Results Archived FFPE tissue sections obtained from 90 pts admitted at Fondazione IRCCS Istituto Nazionale dei Tumori of Milan from October 2017 to April 2019 were analyzed. At the time of this report, 60 samples (66%) had adequate tissue for extended analyses. As expected, 55 (92%) pts had KRAS mutations, while ATM, CDKN2A mutations and microsatellite instability (MSI) were found in 3 (5%), 4( 6%) and 2 (3%) pts, respectively. MGMT promoter methylation was found in 21 pts (35%), of which 13 (61%) had low/negative MGMT protein expression. Of note, amongst MGMT methylated pts, there were 5 (23%) BRCA1/2 somatic mutant and 2 (9%) MSI, suggesting possible genomic instability. Conclusions MGMT is a prognostic and predictive marker in glioblastomas and there is an increasing evidence in its role in metastatic CRC, with phase II studies showing a response rate of 10% in chemorefractory pts with MGMT methylation treated with TMZ. In our single center experience, MGMT methylation was found in 35% of patients with mPAC. This data warrant further prospective confirmation; nevertheless, considering the growing interest in the role of DNA-damage response genes in mPAC, there is definitely a rationale in investigating MGMT methylation as a predictive and prognostic biomarker in mPAC. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure F. Morano: Honoraria (self): Servier. F. Pietrantonio: Advisory / Consultancy: Roche; Advisory / Consultancy: Amgen; Advisory / Consultancy: Lilly; Advisory / Consultancy: Sanofi; Advisory / Consultancy: Bayer; Advisory / Consultancy: Servier; Research grant / Funding (institution): BMS. F.G.M. De Braud: Advisory / Consultancy: TizianaLife Sciences; Advisory / Consultancy, Speaker Bureau / Expert testimony: BMS; Advisory / Consultancy: Celgene; Advisory / Consultancy: Novartis; Advisory / Consultancy: Servier; Advisory / Consultancy: Pharm Research Associated; Advisory / Consultancy: Daiichi Sankyo; Advisory / Consultancy, Speaker Bureau / Expert testimony: Ignyta; Advisory / Consultancy: Amgen; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Octimet Oncology; Advisory / Consultancy: Incyte; Advisory / Consultancy: Teofarma; Advisory / Consultancy: Pierre Fabre; Advisory / Consultancy, Speaker Bureau / Expert testimony: Roche; Advisory / Consultancy: EMD Serono; Speaker Bureau / Expert testimony: Eli Lilly; Speaker Bureau / Expert testimony: Novartis; Speaker Bureau / Expert testimony: Amgen; Speaker Bureau / Expert testimony: AstraZeneca. M. Di Bartolomeo: Advisory / Consultancy: Lilly; Advisory / Consultancy: Servier; Travel / Accommodation / Expenses: Roche. All other authors have declared no conflicts of interest.