P05.23.A TUMOUR SIZE AND GROWTH AS PREDICTORS OF CLINICAL OUTCOMES IN IDH-MUTANT DIFFUSE GLIOMAS: A SYSTEMATIC REVIEW

Abstract BACKGROUND Isocitrate dehydrogenase-mutant (mIDH) diffuse gliomas, including astrocytomas and oligodendrogliomas, initially grow slowly before transitioning to a malignant phase. Despite advances in surgery, radiotherapy, and chemotherapy, survival remains limited. Assessing tumour size and growth rate is crucial but complicated by measurement variability, impacting treatment decisions and outcome prediction. OBJECTIVES This systematic review examines the correlation between tumour size and growth rate measured after resection with overall survival (OS), progression-free survival (PFS), malignant progression-free survival (M-PFS), and symptom burden (seizures, headaches, neurological deficits) in mIDH gliomas. METHODS A comprehensive literature search was conducted in MEDLINE/PubMed, EMBASE, Cochrane Library, and grey literature sources (scientific congresses and health authority communications) from January 1, 2014, to January 17, 2024. Eligible studies focused on adult patients (≥18 years) with mIDH gliomas and assessed post-resection tumour size (diameter or volume) or tumour growth rate, and clinical outcomes such as OS, PFS, M-PFS, time to treatment (TTT), malignant transformation (MT) and symptoms, including seizures, headaches, and neurological deficits. Two independent reviewers screened articles, extracted data, and assessed study quality. RESULTS A total of 56 studies were selected, of which 28 studies met the inclusion criteria and collectively included 11,510 patients. Of these, 25 assessed tumour volume, 1 measured tumour diameter, and 5 examined tumour growth. Most studies (82.1%, n=23) were retrospective. The selected studies classified tumors according to the 2016 WHO classification, with 46.0% (n=5,295) identified as IDH-mutant, 27.3% (n=3,141) as 1p/19q-codeleted, and 5.2% (n=597) as IDH-WT. Most studies identified a significant correlation between residual tumour size/growth rate and OS (85.7%, n=18/21) or PFS (84.6%, n=11/13). Additionally, of the 14 studies assessing a correlation with other outcomes such as M-PFS, symptom progression, MT and TTT, 92.9% (n=12/13) identified an inverse correlation with tumour size or growth rate. Only 6 studies did not demonstrate a significant association between tumour diameter or volume and OS, PFS or M-PFS. Altogether, these findings suggest that residual tumour size and tumour growth rate may serve as predictors of clinical outcomes, including OS, PFS, M-PFS, MT, TTT, and symptoms such as seizures in mIDH diffuse gliomas. CONCLUSIONS Tumour volume and growth rate are significant predictors of clinical outcomes in mIDH gliomas, especially OS and PFS. Implementing volumetric assessment and tumor growth monitoring into clinical practice may enhance the management and follow-up of patients with mIDH gliomas.