Background: A multi-institutional clinical trial was conducted for localized lymphoma. This study evaluated whether a quality assurance (QA) program could clarify the source of variation in radiotherapy treatment between the institutions.
Materials and methods: Two- or three-dimensional treatment planning is required to cover the target volumes adequately and to minimize doses to organs at risk. An original QA tool was used to compare pretreatment images with portal images and dose distribution, concurrently.
Results: In two of the first 12 cases, there was a deviation in the delineation of planning target volume (PTV). The QA committee clarified that there were ambiguities in the definition of PTV The study office distributed a memorandum outlining the definition of PTV in order to reduce deviations. Thereafter, a minor deviation was identified in one of the latter 11 cases.
Conclusion: This QA program clarified the source of variation, and adapted the policy to reduce these problems.