P02.25.A THE IMPACT OF PSEUDOPROGRESSION IN OVERALL SURVIVAL IN GLIOBLASTOMA, EXPERIENCE IN OUR CENTER

Abstract

Abstract BACKGROUND After surgery, standard treatment for glioblastoma (GBM) is temozolomide (TMZ), initially concurrent with radiotherapy (Ct-Rt), and subsequently as maintenance therapy. For adequate tumour response assessment,, magnetic resonance imaging (MRI) is performed one month after completing Ct-Rt. Instead, the radiologic images obtained in that MRI can be difficult to interpret because they may show radiation-induced pseudoprogression (psPD) rather than disease progression. METHODS We analyzed retrospectively clinical and tumor biology characteristics of patients (pts) with GBM treated in our center with Ct-Rt +/- adjuvant Qt and their relationship with psPD (reported by RANO criteria) and impact in overall survival (OS) RESULTS From November-2016 to October-2022, we collected data for 82 pts (median age: 60 years) who underwent Qt-Rt exclusively (25 patients) or Qt-Rt and adjuvant temozolomide (57 patients). Pts characteristics were: male/female 61.4/38.6%, performance status (PS) 0/1/2 10.5/71,9/17.5%, total surgery/subtotal/biopsy 21.1 / 52.6 / 26.3%, MGMT methylated/ not methylated/not realized 52.7/ 45.6 /1.8 %, TERT mutated/not mutated/not realized 29.8 / 7 / 36.8 / 63.2 %, ATRX positive/negative/not realized 75.4 / 14 / 10.5 %, P53: positive/negative 25 / 75 %. After Ct-Rt, MRI for evaluation of response showed: no evidence of disease 13.4%, partial response 4.9%, stable disease 34.1%, progressive disease 18.3% and psPD 26.8%. In multivariate analysis, significant difference of OS were observed in function of type of surgery (better OS in R0; p=0.015), performance status (better OS in PS 0-1; P=0.006), MGMT methylation (better OS in methylated; p=0.037), and ATRX status (better OS in negative; p=0.05). OS was algo significantly increased in pts treated with Qt-Rt and adjuvant Qt (17.7 +/- 1.7 months) vs Qt-Rt exclusively (11.35 +/-1.62 months) (p=0.013). In pts with psPD, OS was significantly superior compared with pts with progressive disease after Qt-Rt treatment (16.6 vs 11.3 months, p=0.048). In our cohort no differences between MGMT methylation status and psPD were observed (MGMT methylated 54.5%/ 45.5 not methylated). CONCLUSION It is essential to differenciate between PsPD and PD because it may have a clinical impact on chemotherapy-based treatment and OS, but it is also neccesary to know patient characteristics and tumor biology in order to identify patients that will beneficiate from TMZ. <!--EndFragment-->