MRI and¹⁸F-FET PET for Multimodal Treatment Monitoring in Patients with Brain Metastases: A Cost-Effectiveness Analysis

PET using the radiolabeled amino acid O-(2-[¹⁸F]fluoroethyl)-l-tyrosine (¹⁸F-FET) has been shown to be of value for treatment monitoring in patients with brain metastases after multimodal therapy, especially in clinical situations with equivocal MRI findings. As medical procedures must be justified socioeconomically, we determined the effectiveness and cost-effectiveness of ¹⁸F-FET PET for treatment monitoring of multimodal therapy, including checkpoint inhibitors, targeted therapies, radiotherapy, and combinations thereof in patients with brain metastases secondary to melanoma or non–small cell lung cancer. Methods: We analyzed already-published clinical data and calculated the associated costs from the German statutory health insurance system perspective. Two clinical scenarios were considered: decision tree model 1 determined the effectiveness of ¹⁸F-FET PET alone for identifying treatment-related changes, that is, the probability of correctly identifying patients with treatment-related changes confirmed by neuropathology or clinicoradiographically using the Response Assessment in Neuro-Oncology criteria for immunotherapy. The resulting cost-effectiveness ratio showed the cost for each correctly identified patient with treatment-related changes in whom MRI findings remained inconclusive. Decision tree model 2 calculated the effectiveness of both ¹⁸F-FET PET and MRI, that is, the probability of correctly identifying nonresponders to treatment. The incremental cost-effectiveness ratio was calculated to determine cost-effectiveness, that is, the cost for each additionally identified nonresponder by ¹⁸F-FET PET who would have remained undetected by MRI. One-way deterministic and probabilistic sensitivity analyses tested the robustness of the results. Results:¹⁸F-FET PET identified 94% of patients with treatment-related changes, resulting in €1,664.23 (€1.00 = $1.08 at time of writing) for each correctly identified patient. Nonresponders were correctly identified in 60% by MRI and in 80% by ¹⁸F-FET PET, resulting in €3,292.67 and €3,915.83 for each correctly identified nonresponder by MRI and ¹⁸F-FET PET, respectively. The cost to correctly identify 1 additional nonresponder by ¹⁸F-FET PET, who would have remained unidentified by MRI, was €5,785.30. Conclusion: Given the considerable annual cost of multimodal therapy, the integration of ¹⁸F-FET PET can potentially improve patient care while reducing costs.