ESTRO 2024 - Abstract Book

S844

Clinical - CNS

ESTRO 2024

Purpose/Objective:

Whole brain radiotherapy (WBRT) is one of the mainstay of treatment of brain metastases especially. But, even though cranial irradiation improves overall survival, the associated neurocognitive deficits and declining quality of life have brought this treatment modality under scrutiny. Radiation-induced injury to the neural stem cells in the hippocampal formation is associated with deficits in learning, memory and spatial processing. The aim of this study is to appraise the feasibility of avoiding hippocampus while delivering WBRT in helical tomotherapy (HT). Also, we aim to evaluate the benefits of HS-WBRT in regards to preventing cognitive decline and assess if the theoretical benefit of sparing hippocampus clinically translate to preservation of neurocognition using standard neurocognitive function(NCF) test instruments. We conducted a prospective study on the feasibility of HS-WBRT in 26 patients who presented with brain metastases and the resulting benefit of hippocampal sparing on NCF. All patients were older than 18 years of age and had karnofsky performance status score> 70. Histopathological evidence of malignancy was procured from all patients. Patients with prior cranial irradiation, lesions involving hippocampus, radiographic evidence of hydrocephalus and/or clinical suspicion of leptomeningeal spread were excluded. Selected patients were planned for HS-WBRT in HT and subsequently underwent CT simulation and MRI brain imaging. After CT-MRI images registeration, contouring was done in accordance with standard contouring guidelines and hippocampal contouring atlas for RTOG 0933. Total dose of 30Gy in 10 fractions was prescribed to PTV and the treatment was delivered ibyRadixact X9 helical tomotherapy (Accuray, Sunnyvale, USA). Conformity and homogeneity of dose distribution were analysed using target coverage (TC), homogeneity index (HI), V90, V95, prescription isodose volume to target volume ratio (PITV) and maximum dose divided by the prescription dose (MDPD). NCF was assessed by test batteries namely HVLT-R and MMSE. Quality of life was evaluated by FACT BR questionnaire. Patients underwent these test batteries prior to the start of WBRT, at completion of RT and monthly till 6 months post radiotherapy. Material/Methods:

Results:

Median age of presentation was 55 years. 54% of patients were males and remaining 46% were females. 77% had KPS score >90. Only 42% of patients presented with solitary lesion in brain and the rest had multiple brain metastases. Overall survival was 92.3%. Mean tumor regression assessed three months post HS-WBRT was 62%. Average PTV volume was 1525.20cc with the maximum volume being 1776.0cc. Dose to 2% volume of PTV was 31Gy± 0.33. Minimum dose to 98% volume of PTV was 26Gy±1.5. D90% was 29.80Gy ±0.2. 96.2% target volume received 95% of prescription dose while 98% volume received 90% of the prescription dose. Average distance between Hippocampus and V95 is 10.17mm. Average time duration for one fraction was 19 minutes±4min. The