Microbeam radiation therapy for lung cancer: a review of experimental setups and biological endpoints in preclinical studies.

Background: Microbeam radiation therapy (MRT) seeks to improve the therapeutic ratio of conventional radiation therapy though the delivery of high doses in micrometre-scale beamlets of synchrotron-generated X-rays.

Purpose: To assess the MRT experimental setups and biological endpoints used in preclinical studies investigating its therapeutic potential in lung cancer models.

Methodology: PubMed, Embase, Science Direct, and Web of Science were searched using the following keywords, 'microbeam', 'micro beam', 'synchrotron' and 'lung'. The reported physical parameters of the MRT set up and biological endpoints chosen to test efficacy were examined.

Main findings: Fourteen studies were assessed. The microbeam widths ranged from 25 µm to 630 µm, and the microbeam spacing ranged from 0 µm to 4000 µm. The peak doses ranged up to 1000 Gy and dose rates ranged from 4 Gy/s to 1.4x10⁴ Gy/s. Fibrosis was the most commonly assessed radiation-induced toxicity.

Conclusion: MRT experimental set ups and biological endpoints are heterogeneous. Standardization could strengthen future evidence supporting its use for the management of patients with lung cancer.