# Observational Management for Patients with Biochemical Recurrence Following Radical Prostatectomy, in the Absence of Detectable Disease on Restaging PSMA PET/CT Imaging

## TL;DR

This study shows that some men with early signs of prostate cancer recurrence after surgery can safely avoid immediate treatment if scans show no cancer spread and they are at low risk.

## Contribution

The study identifies specific risk factors for progression in patients with negative PSMA PET/CT scans at biochemical recurrence.

## Key findings

- Low-risk patients had a 48% lower chance of progression compared to high-risk patients at three years.
- Higher pathological grade and faster PSA doubling time independently predicted biochemical progression.
- Most radiological progression occurred outside the original prostate area in rescanned patients.

## Abstract

Background/Objectives: In men with biochemical recurrence (BCR) after a radical prostatectomy (RP), salvage radiotherapy (SRT) is commonly recommended when imaging shows no metastases. The optimal management for patients with negative prostate-specific membrane antigen (PSMA) PET/CT findings at BCR remains uncertain. This study evaluated outcomes of patients with BCR and negative PSMA PET/CT to identify who may be safely observed and who may benefit from early SRT. Methods: This retrospective multicentre cohort study included 89 patients with BCR and negative PSMA PET/CT findings after a RP (2015–2022) who were managed with observation. The exclusion criteria were PSA levels ≥ 0.8 ng/mL at baseline, prior SRT, or prior or ongoing hormonal therapy. Minimum follow-up was 3 years. Biochemical progression (PSA rise > 0.2 ng/mL above baseline or initiation of additional treatment) and radiological progression (local or metastatic disease on follow-up PSMA PET/CT) were assessed. Patients were stratified by EAU BCR-risk classification. Multivariable Cox regression included age, biochemical persistence (BCP) after a RP, pathological tumour stage (pT), pathological ISUP grade group (pISUP), node status (pN), margin status (R), and PSA doubling time (PSAdt). Results: The median age was 66 years (IQR 60–69) and the median PSA measurement at BCR was 0.2 ng/mL (IQR 0.2–0.3). A total of 27/89 (30%) patients were EAU BCR low-risk and 62/89 (70%) were high-risk. At three years, biochemical progression occurred in 14/27 (52%) low-risk vs. 51/62 (83%) high-risk patients, with time to progression being 21 vs. 12 months (p = 0.01). A pISUP grade group ≥ 4 (HR 2.04 [95%-CI 1.11–3.74]; p = 0.022) and a PSAdt < 20 months (HR 5.72 [95%-CI 2.41–13,56]; p < 0.01) independently predicted biochemical progression. Radiological progression occurred in 43/68 (66%) rescanned patients, with 32/43 (74%) showing disease outside the prostatic fossa. Conclusions: Nearly half of patients with BCR and negative PSMA PET/CT findings who were classified as EAU BCR low-risk remained progression-free at three years. These results support a risk-adapted approach, indicating that SRT may be deferred in selected low-risk patients.