As PSA levels rise in men who have biochemically recurrent prostate cancer (PCa) following definitive treatment, 18F-fluciclovine positron emission tomography (PET) becomes increasingly accurate in detecting lesions, according to a single-institution study.
Joseph M. Armstrong, MD, and collaborators at the University of Utah Health Sciences Huntsman Cancer Institute in Salt Lake City studied 115 men who underwent 18F-fluciclovine PET after experiencing biochemical recurrence (BCR) following radical treatment. PET revealed no concerning lesions in 25 patients (21.7%), a solitary lesion in 32 patients (27.8%), 2 to 5 lesions in 45 patients (39.1%), and more than 5 lesions in 13 (11.3%).
At PSA thresholds below 0.5, 0.5 to 2.0, and greater than 2.0 ng/mL, PET detected lesions in 55.5%, 70.6%, and 91.5% of patients, respectively, Dr Armstrong’s team reported in Urologic Oncology.
“Our results indicate that 18F-fluciclovine PET represents a promising new technology,” the authors wrote.
More than half of PET scans performed for patients with PSA values below 0.5 ng/mL identified discreet lesions, and additional increases in PSA level decreased the proportion of negative scans at each of the PSA thresholds examined, the authors pointed out.
In a receiver operating characteristic (ROC) analysis, the investigators found that the area under the curve was maximized when sensitivity was 60% and specificity was 84%. The corresponding ROC curve was 0.75 and the PSA cutoff at this threshold was 2.1 ng/mL, they reported.
“Our results suggest that in the setting of biochemical recurrence, as a patient’s PSA increases, so does the probability of a positive 18F-fluciclovine PET scan and finding larger numbers of suspicious lesions,” the authors concluded.
Employing a PSA threshold of 1 to 2 ng/mL “carries greater sensitivity and specificity and may maximize identifying individuals with early BCR who may benefit from early intervention, while minimizing negative scans.”
Dr Armstrong and his colleagues noted that identifying specific sites of recurrence correctly may influence the choice of salvage therapy, particularly if focal salvage therapy is under consideration.
Of the 115 men, 61 (53%) underwent surgery alone, 20 (17%) had radiotherapy, and 34 (30%) had a combination of these treatments; 79 had undergone a prior computed tomography scan and 94 had undergone bone scans, with negative findings in the majority of them.
Armstrong JM, Martin CR, Dechet C, et al. F-fluciclovine PET CT detection of biochemically recurrent prostate cancer at specific PSA thresholds after definitive treatment [published online April 18, 2020]. Urol Oncol. doi: 10.1016/j.urolonc.2020.03.021