18F-DCFPyL PET/CT Imaging in Patients with Biochemically Recurrent Prostate Cancer After Primary Local Therapy

Abstract

Our objective was to investigate the lesion detection rate of ¹⁸F-DCFPyL PET/CT, a prostate-specific membrane antigen (PSMA)-targeted PET agent, in patients with biochemically relapsed prostate cancer after primary local therapy. Methods: This was a prospective institutional review board-approved study of 90 patients with documented biochemical recurrence (median prostate-specific antigen [PSA], 2.5 ng/mL; range, 0.21-35.5 ng/mL) and negative results on conventional imaging after primary local therapies, including radical prostatectomy (n = 38), radiation (n = 27), or a combination of the two (n = 25). Patients on androgen deprivation therapy were excluded. Patients underwent whole-body ¹⁸F-DCFPyL PET/CT (299.9 ± 15.5 MBq) at 2 h after injection. The PSMA PET lesion detection rate was correlated with PSA, PSA kinetics, and original primary tumor grade. Results: Seventy patients (77.8%) showed positive PSMA PET results, with a total of 287 lesions identified: 37 prostate bed foci, 208 lesions in lymph nodes, and 42 in distant sites in bones or organs, Eleven patients had negative results, and 9 patients showed indeterminate lesions, which were considered negative in this study. The detection rates were 47.6% (n = 10/21), 50% (n = 5/10), 88.9% (n = 8/9), and 94% (n = 47/50) for PSA levels of >0.2 to <0.5, 0.5 to <1.0, 1 to <2.0, and ≥2.0 ng/mL, respectively. In postsurgical patients, PSA, PSA doubling time, and PSA velocity correlated with PET results, but the same was not true for postradiation patients. These parameters also correlated with the extent of disease on PET (intrapelvic vs. extrapelvic). There was no significant difference in the rate of positive scans between patients with higher-grade and lower-grade primary tumors (Gleason score of ≥4 + 3 vs. <3 + 4). Tumor recurrence was histology-confirmed in 40% (28/70) of patients. On a per-patient basis, positive predictive value was 93.3% (95% confidence interval, 77.6%-99.2%) by histopathologic validation and 96.2% (95% confidence interval, 86.3%-99.7%) by the combination of histology and imaging/clinical follow-up. Conclusion:¹⁸F-DCFPyL PET/CT imaging offers high detection rates in biochemically recurrent prostate cancer patients and is positive in about 50% of patients with a PSA level of less than 0.5 ng/mL, which could substantially impact clinical management. In postsurgical patients, ¹⁸F-DCFPyL PET/CT correlates with PSA, PSA doubling time, and PSA velocity, suggesting it may have prognostic value. ¹⁸F-DCFPyL PET/CT is highly promising for localizing sites of recurrent prostate cancer.

Keywords: DCFPyL; PET; PSMA; biochemical recurrence; prostate cancer.

FIGURE 1.

¹⁸F-DCFPyL PET overall detection rates and intrapelvic and extrapelvic lesion detection rates, stratified by PSA (A), PSAdt (B), and PSAvel (C).

FIGURE 2.

Receiver-operating-characteristic analysis in prostatectomy patients (n = 63) for PSA, PSAdt, and PSAvel.

FIGURE 3.

¹⁸F-DCFPyL–positive sites by location, stratified by PSA.

FIGURE 4.

A 60-y-old man with T2bN0, Gleason 4 + 3 prostate cancer, after prostatectomy. Time from treatment is 4 y, prescan PSA level is 0.24 ng/mL, and PSAdt is 16 mo. ¹⁸F-DCFPyL PET/CT demonstrates focal uptake (arrows) at right seminal vesicle resection site. Patient refused biopsy and proceeded with RT.

FIGURE 5.

A 63-y-old man with T3aN0, Gleason 4 + 3 prostate cancer after prostatectomy. Time from treatment is 0.7 y; prescan PSA level is 0.40 ng/mL, and PSAdt is 2.6 mo. ¹⁸F-DCFPyL PET/CT image shows single 3-mm left presacral node with focal intense uptake (arrows). This lesion was not biopsied, but we consider it less likely to be a dorsal nerve ganglion root because of its location and uptake intensity. Patient proceeded with salvage RT with presacral node boost and ADT. Recent PSA level was 0.02 ng/mL.

FIGURE 6.

A 63-y-old man with T2cN1, Gleason 5 + 4 prostate cancer after prostatectomy. Time from treatment is 1.3 y; prescan PSA level is 0.44 ng/mL, and PSAdt is 2.2 mo. ¹⁸F-DCFPyL PET/CT demonstrates subcentimeter bilateral pelvic nodes and right fifth rib focus (arrows). Biopsy confirmed bone metastasis.

FIGURE 7.

Correlation plots between PSA and PSA kinetics vs. lesion number, SUV_max, and tumor volume.