The involvement of serum serotonin levels producing radiation-induced bystander effects for an in vivo assay with fractionated high dose-rate (HDR) brachytherapy

Abstract

Purpose: The primary goal of this investigation was to observe whether measurable levels of bystander factor(s) can be detected in esophageal carcinoma patients’ urine samples taken after undergoing high dose rate (HDR) intraluminal brachytherapy (ILBT). However, a small pilot study was developed to evaluate whether serotonin [5-Hydroxytryptamine (5-HT)] serum levels play an active role in the mechanisms of radiation-induced bystander effects (RIBE) at high doses.

Materials and methods: In the present study, a colony-forming in vivo assay was developed and used for the detection of non-targeted effects. Samples of urine were collected from five esophageal carcinoma patients undergoing fractionated HDR-ILBT. To observe whether 5-HT modulates the bystander effect at higher doses, different batches of foetal bovine serum (FBS) and 5-HT were tested on the same urine samples before and after brachytherapy.

Results: Some of our data suggests statistically significant evidence for serotonin playing an active role as a signalling molecule at higher doses when patients underwent HDR-ILBT.

Conclusion: However, a more thorough investigation, with a larger sample size, is warranted before serotonin can be known to play a role in bystander effects at this particular dose range and treatment regime.

Keywords::

• Bystander effect
• serotonin (5-HT)
• high dose-rate (HDR) brachytherapy
• esophageal carcinoma
• urine

Acknowledgements

We acknowledge Varian International B.V. for funding part of this study. A special thanks to the brachytherapy and ambulance care staff for helping in sample collection at the Hamilton Health Sciences Juravinski cancer centre (JCC). We would also like to thank Emilia Timotin for all of her help with patient consents and sample collection at the JCC. We acknowledge and thank all the patients who took the time to participate in this study; without these individuals this research would not be possible. We also acknowledge the statistical advice and help from Dr Richard Smith when preparing this manuscript.

Declaration of interest The authors report no declaration of interest. The authors alone are responsible for the content and writing of the paper.