The Utility of PET/CT in External Radiation Therapy Planning of Prostate Cancer

Radiotherapy and radical prostatectomy are the definitive treatment options for patients with localized prostate cancer. A rising PSA after radical prostatectomy indicates prostate cancer recurrence, and these patients may still be cured with salvage radiotherapy. To maximize chance for cure, irradiated volumes should completely encompass the extent of disease. Therefore, accurate estimation of the location of disease is critical for radiotherapy planning in both the definitive and salvage settings. Conventional imaging for prostate cancer has limited sensitivity for detection of disease both at initial staging and at biochemical recurrence. Integration of Positron Emission Tomography (PET) into routine evaluation of prostate cancer patients may improve both staging accuracy and radiotherapy planning. 18F-fluorodeoxyglucose (FDG) PET/CT is now routinely used in radiation planning for several cancer types. However, FDG-PET/CT has low sensitivity for prostate cancer. Additional PET probes evaluated in prostate cancer include 18F-sodium fluoride (Na-F), 11C-acetate, 11C- or 18F-choline, 18F-FACBC (fluciclovine, [Axumin™]), and 68Ga- or 18F- labeled ligands that bind prostate specific membrane antigen (PSMA). PSMA ligands appear to be the most sensitive and specific, but are not yet approved for use in the Untied States. Retrospective and prospective investigations suggest a potential major impact of PET/CT on prostate radiation treatment planning. Prospective trials randomizing patients to routine radiotherapy planning versus PET/CT aided planning may show meaningful clinical outcomes. Prospective clinical trials evaluating the addition of fluciclovine-PET/CT for planning of salvage radiotherapy with clinical endpoints are underway. Prospective trials evaluating the clinical impact of PSMA PET/CT on prostate radiation planning are indicated.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2018 Jan 04 [Epub ahead of print]

Jeremie Calais, Minsong Cao, Nicholas G Nickols

UCLA, United States.