A phase I study on stereotactic body radiotherapy of liver metastases based on functional treatment planning using positron emission tomography with 2-[<sup>18</sup>F]fluoro-2-deoxy-d-galactose

<p><b>Background and purpose:</b> The galactose analog 2-[<sup>18</sup>F]fluoro-2-deoxy-d-galactose (FDGal) is used for quantification of regional hepatic metabolic capacity by functional positron emission tomography computerized tomography (PET/CT). In the present study, FDGal PET/CT was used for functional treatment planning (FTP) of stereotactic body radiotherapy (SBRT) of liver metastases with the aim of minimizing radiation dose to the best functioning liver tissue.</p> <p><b>Material and methods:</b> Fourteen patients referred for SBRT had FDGal PET/CT performed before and one month after the treatment. The planning CT and the FDGal PET/CT images were deformable co-registered.</p> <p><b>Results:</b> A reduction in the mean dose of approximately 2 Gy to the best functioning sub-volumes was obtained. One patient developed grade 2 acute morbidity and no patients experienced grade 3 or higher acute morbidities. The regional hepatic metabolic function post-treatment was linearly correlated to the regional radiation dose and for each 10-Gy increase in dose (γ<sub>10Gy</sub>), the metabolic function was reduced by 12%. A 50% reduction was seen at 22.9 Gy in 3 fractions (CI 95%: 16.7–30.4 Gy).</p> <p><b>Conclusion:</b> The clinical study demonstrates the feasibility for FTP in patients with liver metastases and it was possible to minimize the radiation dose to the best functioning liver tissue.</p>