Detection of prostate cancer lesions using Gallium-68 PSMA-11 PET in men with biochemical recurrence following radical prostatectomy.

Abstract

236 Background: Conventional imaging techniques infrequently detect the site of prostate cancer disease in men with biochemical recurrence following radical prostatectomy (RP). We examine the use of Gallium-68 Prostate-Specific Membrane Antigen (PSMA) positron emission tomography (PET) to determine the site of disease recurrence in these men. Methods: We retrospectively reviewed men with persistently detectable prostate specific antigen (PSA) and those with formal biochemical recurrence (PSA ≥ 0.2 ng/mL) following RP who underwent PSMA PET scan under our institution's prospective trials (NCT02918357 & NCT02611882). We assessed the location of detected recurrences, and examined the distribution of recurrence location (prostate bed, pelvic lymph nodes (LN), and extra-pelvic disease) according to PSA at time of PET scan. Results: One hundred and fifty-eight men underwent PSMA PET after RP, 46% of men had previously undergone either adjuvant or salvage radiation therapy. Eleven men (7%) had the scan for persistently detectable PSA < 0.2 and 93% of men had biochemical recurrence. At time of RP, 66% of men had ≥pT3a disease, 40% had positive surgical margins, and 18% had positive lymph nodes. Gleason grade at RP was ≤3+3 in 5% of men, 3+4 in 27%, 4+3 in 32% and ≥4+4 in 36%. Overall, 77% of men had a lesion detectable on PSMA PET. Men with higher PSA at time of scan had a higher prevalence of lesions, with all men PSA > 6.0 having at least one lesion on PSMA PET (Table). Overall, we found extra-pelvic lesions in 44% of all men, and 58% of men with PSA ≥ 1.0. These are areas not typically covered by salvage radiation fields. Conclusions: PSMA PET detects lesions in a high proportion of men with biochemical recurrence following RP, with many lesions outside of the pelvis. This may facilitate more precise targeting of treatment areas for these patients. Clinical trial information: NCT02918357. Clinical trial information: NCT02611882. [Table: see text]