Prostate cancer patients who have disease recurrence following radical prostatectomy should undergo imaging scans using the imaging agent 68Ga-PSMA-11 to guide their salvage radiotherapy, a new study suggests. The study, by researchers at the University of California, Los Angeles shows that the imaging procedure effectively detects the location of recurrence at an early stage. In 19 percent of patients, the scans identified lesions that wouldn't otherwise be covered by the radiation fields. The study, “68Ga-PSMA-11 PET/CT Mapping of Prostate Cancer Biochemical Recurrence After Radical Prostatectomy in 270 Patients with a PSA Level of Less Than 1.0 ng/mL: Impact on Salvage Radiotherapy Planning,” was published in The Journal of Nuclear Medicine. In practice, volume delineations for prostate cancer salvage radiotherapy (SRT) after radical prostatectomy are normally drawn in the absence of radiographically visible disease. In the absence of visual clues, clinicians delineate a consensus clinical target volume in the prostate and pelvic lymph nodes (areas with potential occult tumor) according to the guidelines of The Radiation Therapy Oncology Group (RTOG) — a panel of experienced genitourinary radiation oncologists. In the study, researchers retrospectively analyzed positron emission tomography/computed tomography (PET/CT) scans of 270 patients who had biochemical recurrence of prostate cancer after radical prostatectomy, but had not received prior radiotherapy. The scans had been performed using the radioactive agent 68Ga-PSMA, which targets the prostate-specific membrane antigen (PSMA). The scans were taken when patients had serum PSA levels below 1 ng/ml — a level at which standard of care imaging is insensitive for detecting recurrence.