Bayesian methods provide a practical real-world evidence framework for evaluating the impact of changes in radiotherapy

Isabella Fornacon-Wood, Hitesh Mistry, Corinne Johnson-Hart, Corinne Faivre-Finn, James P B O'Connor, Gareth J Price

Research output: Contribution to journalArticlepeer-review


PURPOSE: Retrospective studies have identified a link between the average set-up error of lung cancer patients treated with image-guided radiotherapy (IGRT) and survival. The IGRT protocol was subsequently changed to reduce the action threshold. In this study, we use a Bayesian approach to evaluate the clinical impact of this change to practice using routine 'real-world' patient data.

METHODS AND MATERIALS: Two cohorts of NSCLC patients treated with IGRT were compared: pre-protocol change (N = 780, 5 mm action threshold) and post-protocol change (N = 411, 2 mm action threshold). Survival models were fitted to each cohort and changes in the hazard ratios (HR) associated with residual set-up errors was assessed. The influence of using an uninformative and a skeptical prior in the model was investigated.

RESULTS: Following the reduction of the action threshold, the HR for residual set-up error towards the heart was reduced by up to 10%. Median patient survival increased for patients with set-up errors towards the heart, and remained similar for patients with set-up errors away from the heart. Depending on the prior used, a residual hazard ratio may remain.

CONCLUSIONS: Our analysis found a reduced hazard of death and increased survival for patients with residual set-up errors towards versus away from the heart post-protocol change. This study demonstrates the value of a Bayesian approach in the assessment of technical changes in radiotherapy practice and supports the consideration of adopting this approach in further prospective evaluations of changes to clinical practice.

Original languageEnglish
Pages (from-to)53-58
Number of pages6
JournalRadiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
Publication statusPublished - Nov 2022


  • Humans
  • Radiotherapy Planning, Computer-Assisted/methods
  • Bayes Theorem
  • Retrospective Studies
  • Radiotherapy, Image-Guided/methods
  • Radiotherapy Setup Errors
  • Lung Neoplasms/radiotherapy

Research Beacons, Institutes and Platforms

  • Manchester Cancer Research Centre


Dive into the research topics of 'Bayesian methods provide a practical real-world evidence framework for evaluating the impact of changes in radiotherapy'. Together they form a unique fingerprint.

Cite this