Case Study of Anti-1-Amino-3-F-18 Fluorocyclobutane-1-Carboxylic Acid (Anti-[F-18] FACBC) to Guide Prostate Cancer Radiotherapy Target Design

Purpose of the Report: Anti-1-amino-3-F-18 fluorocyclobutane-1-carboxylic acid (FACBC) is a novel radiotracer, which has shown some promise for use with positron emission tomography (PET)/computed tomography (CT) for visualizing prostate cancer. Here we describe a case of a prostate cancer patient who underwent radiation treatment and had an FACBC scan obtained as part of a pilot study. Methods: We explored the potential impact of FACBC on treatment planning. We registered the FACBC acquisition with the PET/CT, which required a simple translation. Then, we did a deformable image registration of the PET/CT with the planning CT-this process allowed the FACBC-defined gross tumor volume (GTV(FACBC)) to be projected into the planning CT. An intensity-modulated radiotherapy (IMRT) plan (plan A) not including GTV(FACBC) (with final dose to 81.0 Gy) was generated, as was an IMRT plan including the GTV(FACBC) to a final dose of 86.4 Gy (plan B). Target coverage and normal tissue dose volume histogram (DVH) endpoints were tabulated. Results: In this particular patient, bladder constraints could not be met on any plan due to anatomic limitations. However, the impact on the rectal DVH could be assessed, and inclusion of the GTV(FACBC) did permit rectal DVH constraints to be met in plan B while maintaining target coverage and inhomogeneity constraints. Conclusion: In our test case, it was feasible to use FACBC to guide IMRT, and highlights the role of deformable image registration of the PET/CT with the planning CT. These findings can guide future studies incorporating FACBC into treatment planning.