Using Breath, Cell Free DNA and Image Analysis to PRedIct Normal TissUe and Tumour Response During Prostate Cancer SBRT

Personalisation of radiotherapy dose based on real-time assessments of normal tissue and tumour response would maximise cure and minimise treatment related toxicity. During a 5 fraction course of prostate Stereotactic Body Radiotherapy (SBRT) this pilot study will assess whether a number of different biomarker approaches can predict for normal tissue and tumour response. Firstly the investigators will analyse volatile organic compounds released within the breath with each fraction of treatment. Secondly the investigators will analyse cell free normal tissue and tumour DNA released during treatment. Thirdly the investigators will develop imaging processing algorithms to look for imaging biomarkers predicting rectal wall toxicity using pre and post treatment cone beam CT verification images. Each of these approaches will be assessed against prostate specific antigen (PSA), Common Terminology Criteria for Adverse Events (CTCAE v4.0) criteria and Expanded Prostate Cancer Index Composite (EPIC-26) patient reported outcomes with a maximum of 24 months of follow up.