68Ga-PSMA-11 Yields Positive Results in Intermediate/High-Risk Prostate Cancer Following Surgical Intervention

Patients with intermediate to high-risk prostate cancer who received ⁶⁸Ga-PSMA-11 PET after undergoing a radical prostatectomy and lymph node dissection experienced positive results, according to results from a study published in JAMA Oncology.

⁶⁸Ga-PSMA-11 PET yielded positive results in 14% of patients with pelvic nodal disease, 1% with extra pelvic nodal disease, and 3% with metastatic bone disease. The treatment also yielded a sensitivity of 0.40 (95% CI, 0.34-0.46), specificity was 0.95 (95% CI, 0.92-0.97), positive predictive value was 0.75 (95% CI, 0.70-0.80), and negative predictive value was 0.81 (95% CI, 0.76-0.85).

The prospective multicenter open label single arm phase 3 trial was conducted at the University of California, Los Angeles (UCLA; NCT03368547) and the University of California, San Francisco (NCT02611882 and NCT02919111). A total of 764 patients with a median age of 69 enrolled at either the University of California, San Francisco (n = 364) or UCLA (n = 400).

A total of 36% (n = 277) of patients underwent proctectomy with lymph node dissection, and 27% (n = 75) of those patients had pelvic nodal metastasis. Among patients who had regional pelvic nodal metastasis (n = 75), involvement was frequently unilateral (60%), bilateral (63%), and 23% had another type of involvement. In total, 4683 nodes removed at a median of 17 nodes per patient; 5.5% of patients had no lymph nodes reported.

In a retrospective review wherein investigators reviewed false positives and obtained post-surgery follow-up, 50% (n = 5/10) of patients had persistent prostate specific antigen following surgery. Moreover, a post-surgery ⁶⁸Ga-PSMA-11 PET scan identified the same PET-positive lymph nodes that were previously revealed via post-surgical scan. If these nodes were considered as a true positive lesions, the sensitivity would be 0.44 (95% CI, 0.33-0.55), specificity 0.97 (95% CI, 0.94-0.99), and positive predictive value and 0.88 (95% CI, 0.74-0.95).

Interreader agreement was substantial on right-sided nodes (κ = 0.61; 95% CI, 0.55-0.67), and left-sided nodes (κ = 0.66; 95% CI, 0.60-0.71). Other nodes had moderate interreader agreements (κ = 0.52; 95% CI, 0.46-0.58).

In total, 64% of patients did not undergo a proctectomy, and 108 patients had no follow-up data. Additionally, the unblinded local reads were positive for positive for pelvic lymph node disease (52%), extra pelvic lymph node disease (10%), and metastatic bone disease (13%). Investigators reported that among those with follow up 69% of patients who did not have surgery underwent radiotherapy, 22% received systemic therapy, 4% underwent surveillance, and 5% had other treatments.

Patients did not experience any adverse effects (AEs) higher than grade 1. A total of 6% (n = 44) of patients had grade 1 AEs with no intervention needed. The most common AEs were diarrhea (2%), and fatigue (1%). Four patients each reported rash and nausea. The AEs were not related to the study drug and could be related to contrast administration.

Reference

Hope TA, Eiber M, Armstrong WR, et al. Diagnostic accuracy of 68Ga-PSMA-11 PET for pelvic nodal metastasis detection prior to radical prostatectomy and pelvic lymph node dissection: a multicenter prospective phase 3 imaging trial. JAMA Oncol. Published Online September 16, 2021. doi:10.1001/jamaoncol.2021.3771