MATERIAL and METHODS: In our study, we included 169 glioblastoma patients who were admitted to our clinic between 2009 and 2019 and received concurrent radiotherapy (RT) + temozolomide (TMZ) after surgery. Patients were collected retrospectively and analyzed using appropriate statistical methods.

RESULTS: The average follow-up period was 19 months. The average overall survival (OS) was 20.5 months. PFS and PPS were found to be 10.8 and 8.9 months, respectively. In the multivariate analysis for prognostic factors on OS, the Karnofsky Performance Score (KPS), the extent of resection (EOR), and the use of adjuvant TMZ were significant. PFS was significantly predicted by KPS, EOR, adjuvant TMZ, and planning target volume (PTV). Acute severe lymphopenia (ASL) following RT reduced the OS and PFS. There was no statistical difference in OS, PFS, recurrence patterns, or ASL incidence between the RTOG and EORTC regimens and RT techniques (IMRT vs. 3D-CRT). The association between dose-volume parameters (V3, V5, V10, V15, and V20 and V25, V30, V40, and V60 Gy) and post-treatment ASL frequency was studied. For each parameter, threshold levels were discovered. Furthermore, patients with recurrent glioblastoma who received salvage therapies had better outcomes.

CONCLUSION: A multidisciplinary, and intensive treatment approach using modern techniques improved the OS of glioblastoma patients. Furthermore, in glioblastoma patients, larger RT fields were not associated with better outcomes. As a result, lymphocytesparing RT may be more beneficial in increasing patients? compliance to adjuvant TMZ, which is an important prognostic factor of OS. Keywords : Glioblastoma, Radiotherapy, Lymphopenia, Temozolomide, IMRT