# Challenges of Applying the RANO-BM Criteria for Characterization of Brain Metastases Treatment Response

## TL;DR

This paper reviews the RANO-BM criteria for assessing brain metastases treatment response and highlights its limitations and potential improvements.

## Contribution

The paper identifies limitations of the RANO-BM criteria in specific clinical scenarios and suggests possible modifications for future assessment systems.

## Key findings

- The RANO-BM criteria have limitations in certain clinical situations despite recent enhancements.
- Proposed modifications include lowering the measurable disease size threshold and using tumor volumetric analysis.
- A more comprehensive brain metastases response assessment system may require further refinement.

## Abstract

Brain metastases treatment response assessment is an essential component of clinical trials and standard patient care. Therefore, its scope, sensitivity, and adaptability to a wide range of clinical scenarios are of great importance. This work provides a comprehensive review of the current standard brain metastases response assessment methodology proposed by the RANO-BM (Response Assessment in Neuro-Oncology working group for Brain Metastases) and its limitations when applied to specific clinical situations. The review is complemented by a discussion of possible modifications to the RANO-BM guidelines which may contribute to the development and refinement of future brain metastases response assessment systems.

The goal of brain metastasis therapy is to reduce the risk of intracranial disease progression and to minimize treatment-related adverse effects and loss of neurologic function without compromising extracranial disease control. A response assessment system plays a critical role in the comparative evaluation of therapeutic strategies in clinical trials and in routine patient care. Since 2015, the RANO-BM criteria have become a standard schema for evaluating brain metastases treatment response, providing uniform definitions and methodology particularly practical in prospective clinical trials of systemic therapy. There have been a variety of modifications and additions to the original guidelines proposed to improve their utility for brain metastases response assessment, including lowering the measurable disease size threshold, optimizing disease progression metrics, and employing tumor volumetric analysis using automated measurement tools. However, despite these enhancements, the criteria display limitations in selected clinical scenarios. This article provides a detailed overview of these limitations and their corresponding clinical contexts and concludes with a discussion of approaches which may aid in the development of a more comprehensive brain metastases response assessment system.