Next-generation sequencing (NGS) for identifying actionable molecular alterations in patients with newly diagnosed and recurrent IDHwt-glioblastoma (GBM): A large mono-institutional experience.

Abstract

3139 Background: NGS panels allow the identification of alterations within hundreds of cancer-related genes and can guide a personalized strategy in glioma treatment. Methods: From Nov 2019 to Jan 2022 at Veneto Institute of Oncology, Padua, Italy, a large cohort of IDHwt-GBM tissues was analyzed by NGS (FoundationOneCDx). We identified all potential actionable molecular alterations at diagnosis and/or at recurrence. High tumor mutational burden (TMB) was defined as ≥10 mutations/megabase. Results: We analyzed 429 IDHwt-GBM samples: NGS profile was available for 419 samples (97.7%); sample failures in 10 cases (2.3%). 351 (84%) and 68 (16%) GBM samples derived from surgery at diagnosis and recurrence, respectively. All patients received radiotherapy and/or temozolomide as first line therapy. Among all the analyzed samples, the most frequent actionable molecular alterations were: CDKN2A (57%), CDKN2B (53%), EGFR amplification (39%), EGFR mutation (24%), PTEN loss (27%), RB1 (23%), NF1 (18%), PIK3CA (18%), CDK4 (15%), MDM2 (10%), PDGFRA (8%), BRCA1-2 (7%), FGFR1-3 (7%), Myc (6%), JAK (6%), ROS1 (5%), METmut (2%), METampl (2%), BRAF V600E (2%). No NTRK1/2/3 druggable alterations were observed. High TMB was found in 18 samples. Incidence of actionable molecular alterations in newly diagnosed and relapsed GBM samples is described in the Table. The incidence of alteration of EGFR (ampl/mut), RB1, PIK3CA was statistically different between the two subgroups of samples (Fisher test). To date, 10% of patients received a personalized treatment as compassionate use, off-label use or in clinical trials (9 Dabrafenib/Trametinib, 8 Alpelisib, 3 Erdafitinib, 2 Ipatasertib, 1 Alectinib, 1 Capmatinib, 1 Palbociclib, 1 Entrectinib, 1 Pamiparib). Activity analysis is still ongoing. Conclusions: NGS is feasible in GBM samples. Potentially, a high rate of patients could receive a personalized treatment. The activity analysis is ongoing. However, the incidence of actionable molecular alterations may differ between diagnosis and recurrent GBM samples. [Table: see text]