Room: AAPM ePoster Library
Purpose: Patient interfraction anatomical changes observed via daily imaging can warrant replanning of radiotherapy treatments. This may require a new simulation and patient-specific measurement QA, delaying treatment by multiple days. For some patients, this can result in further anatomical changes during the delay. This work presents a fast adaptive replanning strategy using a commercial 3DCRT optimizer for patients presenting with interfraction anatomy changes.
Methods: Three previously treated clinical cases were replanned as field-in-field (FiF) treatments using a commercial fluence-based FiF optimizer to investigate the feasibility of the platform for the development of an adaptive workflow. The replanning scenarios were: a 3DCRT bladder treatment with day-to-day target geometry variation, a VMAT lung treatment with two targets displaying more respiratory motion than initially accounted for, and a VMAT thoracic multi-metastatic treatment with two targets with 12-cm separation. Each scenario was timed and replanned using updated target contours and the corresponding target D95% was compared between the replan and original plan.
Results: The bladder treatment and two lung treatments were replanned using corrected target volumes based on daily CBCTs, resulting in PTV D95% improvements from 96.9% to 100.8%, 97.5% to 99.6%, and 90.7% to 100.9%, respectively. The lung plan organ doses were well below clinical limits. The thoracic treatments were replanned successfully using FiF with similar quality to VMAT. The commercial FiF optimizer allowed for expedited replanning, taking 11.2±4.2 minutes on average, enabling a feasible online adaptation when paired with an abbreviated approval and physics check workflow.
Conclusion: The FiF optimizer showed potential for fast adaptive replanning for cases that exhibit interfraction geometric changes that compromise treatment quality. Further work is underway to test additional scenarios and optimize overlapping organ sparing in plans delivered by FiF versus VMAT. This method could provide a useful clinical tool with minimal alterations to workflow and equipment.