# Biomarkers in Stereotactic Ablative Radiotherapy: Current Evidence and Future Directions

## TL;DR

This review explores biomarkers that can help personalize stereotactic ablative radiotherapy for better cancer treatment outcomes.

## Contribution

The paper provides a comprehensive overview of current and future biomarker strategies specific to SABR.

## Key findings

- Circulating tumor DNA and extracellular vesicles show promise as predictive biomarkers for SABR.
- Radiomic features and immunological markers are being integrated into clinical trials for SABR.
- Standardization and validation are critical for translating biomarkers into clinical practice.

## Abstract

Stereotactic ablative radiotherapy (SABR) has revolutionized the management of patients with oligometastatic and selected primary cancers due to its ability to deliver highly conformal, high-dose radiation in few fractions with minimal toxicity. However, the biological heterogeneity among patients treated with SABR results in variable outcomes, emphasizing the need for predictive and prognostic biomarkers to guide patient selection and post-treatment management. This narrative review discusses the current landscape of biomarker development in the context of SABR across tumor types. Key classes include circulating tumor DNA (ctDNA), extracellular vesicles (EVs), radiomic features, and immunological markers. We highlight the role of each biomarker category in refining therapeutic approaches, their integration into ongoing clinical trials, and future directions for personalized SABR paradigms. Translating these promising biomarker strategies into clinical SABR workflows will require further standardisation, validation, and regulatory alignment.