Volumetric Analysis: Rethinking Brain Metastases Response Assessment
B Ocaña-Tienda, J Pérez-Beteta, JA Romero-Rosales, B Asenjo, A Ortiz, LA Pérez Romasanta, JD Albillo, F Nagib, M Vidal Denis, B. Luque, E. Arana, VM Pérez-García
Neuro-Oncoloy Advances 6(1), 1-9 (2024)
MOLAB authors
Pérez García, Victor M.. Pérez Beteta, Julián. Albillo Labarra, José David. Asenjo Martínez, Beatriz. Luque Sánchez, Belén. Pérez Romasanta, Luis. Ocaña Tienda, Beatriz. Ortíz de Mendivil, Ana. Romero Rosales, José Antonio. Romero Rosales, José Antonio. 
Abstract
Background: The Response Assessment in Neuro-Oncology for Brain Metastases (RANO-BM) criteria are the gold standard for assessing brain metastases (BMs) treatment response. However, they are limited by their reliance on one dimension, despite the routine use of high-resolution T1-weighted MRI scans for BMs, which allows for 3D measurements. Purpose: Our study aimed to investigate whether volumetric measurements could improve the response assessment in patients with BMs. We sought to compare the performance of RANO-BM with criteria based on fractional variations of the total volumes. Materials and Methods: We retrospectively evaluated a dataset comprising 783 BMs and analyzed the response of 185 of them from 132 patients who underwent stereotactic radiotherapy between 2007 and 2021 at five hospitals. We used T1-weighted MRIs to compute the volume of the lesions. For the volumetric criteria, recurrence was defined as at least a 30% increase in volume, and partial response was characterized by a 20% volume reduction. Results: Our study showed that the proposed volumetric criteria outperformed the RANO-BM criteria in several aspects: 1) Evaluating every lesion, while RANO-BM failed to evaluate 71.9% of them. 2) Classifying response effectively in 140 lesions, compared to only 72 lesions classified by RANO-BM. 3) Identifying BM recurrences a median of 3.3 months earlier than RANO-BM criteria. Conclusion: Our study demonstrates the superiority of volumetric criteria in improving the response assessment of BMs compared to the RANO-BM criteria. Our proposed criteria allow for evaluation of every lesion, regardless of its size or shape, better classification, and enable earlier identification of recurrent lesions. Volumetric criteria provide a standardized, reliable, and objective tool for assessing treatment response.