Prospective evaluation of 18F-DCFPyL PET/CT in biochemically recurrent prostate cancer: Analysis of lesion localization and distribution.

Abstract

5556 Background: 18F-DCFPyL, a promising PET agent targeting prostate specific membrane antigen (PSMA), is prospectively evaluated in a single academic center for detecting recurrent lesions in prostate cancer patients with biochemical recurrence (BCR). Methods: We prospectively enrolled 150 men (51-91 years old, mean ± SD: 70.3±7.5) with biochemical recurrence (PSA median 2.38 ng/mL, range 0.12 to 698.4) after primary definitive treatment with prostatectomy (65%), radiotherapy (35%) or both (19%). The 18F-DCFPyL positive lesions compatible with prostate cancer were evaluated by two independent readers. Impact of 18F-DCFPyL PET/CT on patient management was recorded from clinical chart review. Results: 18F-DCFPyL PET/CT had an overall positivity rate of 83% (125 scans), which increased with higher prostate specific antigen (PSA) levels (ng/mL): 63% (PSA < 0.5), 75% (0.5≤PSA < 1), 91% (1≤PSA < 2), 95% (2≤PSA < 5) and 98% (PSA≥5), respectively. In the cohort who underwent prostatectomy, 18F-DCFPyL PET/CT had higher positivity rate in patients with shorter PSA doubling time (PSAdt) (94% in PSAdt 0-3 months vs. 53% in PSAdt > 12 months, P< 0.01). No difference of 18F-DCFPyL positivity rate was observed in post-radiation patients with different PSAdt, nor were there differences between patients with low grade (Gleason 6) or higher-grade prostate cancer (Gleason 7-10). 20 patients (13%) had lesions in the prostate bed only and 41 patients (27%) had oligometastatic disease (1-3 lesions), making them candidates for locally targeted therapy. We identified a total of 1455 18F-DCFPyL positive lesions, including 51 lesions in the prostate bed, 271 pelvic and 463 extra-pelvic lymph nodes, approximately 585 osseous lesions, including 5 patients with diffuse osseous metastases, and 85 lesions in other organs (most commonly in the lungs). 91 out of 150 patients (61%) had change in treatment after 18F-DCFPyL PET and, most noticeably, 48 of these patients (32% total) had lesions only localized on 18F-DCFPyL PET/CT despite negative conventional imaging. Conclusions: 18F-DCFPyL PET/CT holds great potential to be a “one-stop shop” diagnostic tool in the work-up of BCR prostate cancer, with high (61%) impact on the management of these patients. Clinical trial information: NCT03501940 .