Clinical experience of implementing an adaptive treatment decision-making pathway for lung and H&N radiotherapy

Abstract

Background: During radiotherapy, anatomical changes such as weight loss or tumor shrinkage can compromise treatment accuracy, risking healthy tissue toxicity or tumor under-dosing. This work utilises on-treatment cone-beam CT (CBCT) images, enhanced within the treatment planning system tool to create “Corrected CBCTs” [1]. This allows for accurate dose recalculation based on the patient's daily anatomy.

Aims: To evaluate the clinical feasibility of the Corrected CBCTs to quantitatively assess anatomical changes in lung and head and neck (H&N) patients and to establish an integrated clinical workflow for adaptive replanning.

Methods: An adaptive radiotherapy workflow was developed incorporating Corrected CBCT functionality. Retrospective lung and H&N datasets were used to validate the anatomical and dosimetric accuracy of the Corrected CBCTs. The performance of rigid versus deformable image registrations was analysed, and specific assessment criteria were formulated to identify patients requiring a replan.

Results: No clinically significant anatomical differences were found between standard and Corrected CBCTs; dose differences were within 2% for both sites. The assessment criteria for lung replanning was defined as a change in Planning Target Volume D50% within 2% of the prescription, alongside specific Organ at Risk (OAR) constraints. For H&N plans, the evaluation highlighted the necessity of Medical Physics Expert (MPE) input in the adaptive decision

Conclusion: This work demonstrates the successful clinical implementation of Corrected CBCTs for adaptive radiotherapy for lung and H&N treatments. This approach provides a robust, quantitative method for identifying anatomical changes, ensuring more accurate and personalised treatment delivery for lung and H&N patients.