Three Months PSA Response after PSMA-Guided Approach for Biochemical Relapse after Prostatectomy (PSICHE Trial).

Abstract

Prostate bed salvage radiotherapy (SRT) is currently the main approach for early biochemical relapse (BR) after radical prostatectomy (RP). Nonetheless, 68Ga-PSMA-11 PET/CT implementation in this scenario prompted significant changes in patients' management. Our trial is aimed to prospectively assess the oncological outcomes after a pre-defined, 68Ga-PSMA-11 PET/CT based treatment strategy. In this analysis, we present early results focusing on three-months biochemical outcomes after treatment. Inclusion criteria were BR after RP (PSA ≥0.2 ng/ml; < 1 ng/ml) +/- postoperative SRT. All patients with PSA persistence after RP (PSA >0.2 ng/ml within 16 weeks from surgery) were excluded from the trial. After centralized 68Ga-PSMA PET/CT, a pre-defined treatment approach was proposed, consisting in Observation and re-staging at further PSA progression in case of negative 68Ga-PSMA PET/CT and previous postoperative RT, prostate bed SRT in case of negative imaging or positive imaging within prostate bed, Stereotactic body radiotherapy (SBRT) to all sites of disease in patients with pelvic nodal recurrence or oligometastatic disease (defined as (< 3 non-visceral metastatic lesions) or Androgen deprivation therapy +/- other systemic treatment indicated for hormone sensitive prostate cancer for widespread metastatic disease. PSA ≤0.2 ng/ml or ≤ 50% of baseline were defined as Complete or partial biochemical response (CBR or PBR), respectively. At present, 135 patients were enrolled within the protocol. Current analysis is focused on a cohort of patients with at least three months of follow up and excludes all patients who underwent only observation after re-staging due to previous prostate bed SRT (n = 42). In this subgroup, PBR or CBR were detected in 28 (66.7%) and 25 (59.5%) patients, respectively. PSA reduction if compared to baseline was detected in 34 patients, for an overall biochemical response rate of 80.9%. Biochemical progression after treatment was reported in 3 patients, who underwent a second 68Ga-PSMA PET/CT re-staging with detection of distant metastases. Promising results after a 68Ga-PSMA PET/CT targeted salvage treatment strategy were reported in terms of early biochemical response. This approach may allow to defer systemic treatment in this setting. Biochemical relapse free and progression free survival will be the objects of further analysis after longer follow-up.