Session Item

Cost and time efficacy as well as reduced systematic uncertainties have been the main motives for MRI-only radiotherapy (RT). Reduced registration uncertainty may be exchanged to reduced treatment margins and smaller treatment volumes. However, implementation of new techniques may increase complexity (e.g. additional QA), which is associated with additional costs.

The aim of this study was to analyze the actual costs of an MRI-only workflow in comparison to a combined CT/MRI workflow for treating prostate cancer. Further, the economic aspects of MRI-only prostate RT were assessed using late rectal bleeding as a model for side effects.

Following a documented clinical implementation at Skåne University Hospital all tasks and their associated costs were registered for MRI-only as well as for the CT/MRI workflow. During an initial development phase, QA procedures specific for MRI-only were assumed necessary, while these were excluded for long-term clinical use. The synthetic CT (sCT) cost can vary widely between methods and was set as unknown to generalize the calculation (=0). Price lists from 2019 were used for cost estimations.

Treatment plans for PTV margins of 5-10 mm were created and optimized for ten prostate cancer patients prescribed 78Gy/39 fractions. The risk of grade 2+ late rectal bleeding for each plan was calculated using the QUANTEC recommended NTCP model**. The cost of late rectal bleeding was calculated by multiplying the estimated risk of the side effect for the study population with the costs related to the required diagnostic examinations (rectoscopy and hospital visits). Medical or pharmaceutical treatment of the side effect and change in quality of life were not considered.

Associated costs for the MRI-only implementation are shown in Figure 1. Excluded CT examination and faster target delineation were the main contributors to cost reductions. Additional QA procedures for fiducial marker identification and the sCT limited the short-term cost reduction to 21 EUR/patient. On long-term use, assuming a more time efficient workflow in combination with excluded extra QA, costs were reduced by 240 EUR/patient.

A margin reduction from 7 to 5 mm resulted in a mean population probability of late rectal bleeding of 9.7% and 6.0%, respectively. With an associated diagnostic cost of 1180 EUR/patient, the 2 mm margin reduction resulted in a reduced cost of 43 EUR/patient.

The implementation of an MRI-only workflow is associated with reduced costs due to time efficacy as well as reduced rectal toxicity, compared to a combined CT/MR workflow. For MRI-only radiotherapy to be cost-saving, the sCT cost should not exceed 283 EUR/patient.

The main contributor of the MRI-only cost reduction is exclusion of the CT-examination. On a short-term basis, the economic benefit is limited due to the extra costs of QA procedures. The economic benefits of MRI-only are first seen when the workflow is well established, and margin reduction has been included.