• Ashesh B Jani, Eduard Schreibmann, Peter J Rossi, Joseph Shelton, Karen Godette, Peter Nieh, Viraj A Master, Omer Kucuk, Mark Goodman, Raghuveer Halkar, Sherrie Cooper, Zhengjia Chen, and David M Schuster.
• Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, Georgia abjani@emory.edu.
• J. Nucl. Med. 2017 Mar 1; 58 (3): 412-418.

AbstractThe purpose of this study was to evaluate the role of the synthetic amino acid PET radiotracer 18F-fluciclovine in modifying the defined clinical and treatment-planning target volumes in postprostatectomy patients undergoing salvage radiotherapy and to evaluate the resulting dosimetric consequences to surrounding organs at risk. Methods: Ninety-six patients were enrolled in a randomized, prospective intention-to-treat clinical trial for potential salvage radiotherapy for recurrent prostate cancer after prostatectomy. The initial treatment plan was based on the results from conventional abdominopelvic CT and MRI. The 45 patients in the experimental arm also underwent abdominopelvic 18F-fluciclovine PET/CT, and the images were registered with the conventional images to determine whether the results would modify the initial treatment plan. The 51 patients in the control arm did not undergo 18F-fluciclovine PET/CT. For each patient, the clinical and treatment-planning target volumes that would have been treated before 18F-fluciclovine registration were compared with those after registration. For organs at risk (rectum, bladder, and penile bulb), the volumes receiving 40 Gy and 65 Gy before registration were compared with those after registration. Statistical comparisons were made using the paired t test. Acute genitourinary and gastrointestinal toxicity as defined by the Radiation Therapy Oncology Group was compared between the control and experimental arms using the χ2 test. Results: In 24 cases, radiotherapy was planned to a clinical target volume consisting of the prostate bed alone (CTV) (64.8-66.6 Gy). In 21 cases, radiotherapy was planned to a clinical target volume consisting of the pelvis (CTV1) (45.0 Gy) followed by a boost to the prostate bed (CTV2) (19.8-25.2 Gy). In each case, the respective treatment-planning target volume expansion (PTV, PTV1, or PTV2) was 0.8 cm (0.6 cm posterior). With the exception of PTV2, all postregistration volumes were significantly larger than the corresponding preregistration volumes. Analysis of the rectum, bladder, and penile bulb volumes receiving 40 Gy and 60 Gy demonstrated that only the penile bulb volumes were significantly higher after registration. No significant differences in acute genitourinary or gastrointestinal toxicity were observed. Conclusion: Including information from 18F-fluciclovine PET in the treatment-planning process led to significant differences in the defined target volume, with higher doses to the penile bulb but no significant differences in rectal or bladder dose or in acute genitourinary or gastrointestinal toxicity. Longer follow-up is needed to determine the impact of 18F-fluciclovine PET on cancer control and late toxicity endpoints.© 2017 by the Society of Nuclear Medicine and Molecular Imaging.

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