Genetic Markers Correlated With Progression-Free Survival Times In Glioblastoma Patients Undergoing Treatment With Tumor Treating Fields

Abstract INTRODUCTION Despite advances in surgical approaches, followed by chemo-radiotherapy protocols, the overall prognosis for patients with glioblastoma remains poor. Clinical trials have demonstrated that the use of low intensity alternating electric fields, known as Tumor Treating Fields (TTFields), via the Optune™ device extends overall survival times when combined with standard chemotherapy. However, the response to TTFields varies across patients, and it is currently unclear why some patients show increased time to tumor progression with TTFields treatment while others do not. One possible answer lies in the biological diversity of the tumors themselves. Genetic alterations are known to impact survival times and chemotherapy sensitivity in glioblastoma, suggesting that certain markers may also predict responsiveness to TTFields. Here, we compare the genetic profile of primary glioblastoma tumors with progression times in patients receiving TTFields treatment. METHODS Patients with primary glioblastoma who chose treatment with the Optune™ device were prospectively enrolled and a sample from their primary tumor resection was sent for FoundationONE CDx™ testing. Genetic alteration results, including mutation burden and copy number alterations, were then compared with clinical data and tumor progression times. RESULTS Mutations and/or copy number changes in genes that regulate cell growth/proliferation, apoptosis, and interactions with DNA were among the most common alterations observed in our cohort. For patients that recurred within 12 months, we found a common pattern of alterations that includes CDKN2A/2B co-deletion, MTAP deletion, and PIK3 mutations. This pattern was not observed in patients that recurred after 12 months. CONCLUSION The identification of genetic markers that predict treatment responsiveness may help direct patients toward optimal treatment options. Ongoing work is aimed at expanding our sample size, correlating these genetic markers with overall patient survival, and determining if this pattern of expression is specifically related to TTFields treatment response.