Session: MP11: Prostate Cancer: Advanced (including Drug Therapy) I
MP11-06: The prognostic role of 68Ga-PSMA PET/CT and the impact of Metastasis-Directed Therapy on cancer progression in men with biochemical recurrence from prostate cancer. Results from a large, single Institution series.
Introduction: Use of 68Ga-PSMA PET is recommended for prostate cancer (PCa) re-staging in patients with either PSA persistence or biochemical recurrence (BCR) after radical prostatectomy (RP). Since evidence on the role of metastasis directed therapy (MDT) on progression-free survival (PFS) is still poor, we aimed at assessing, in patients with positive PSMA PET, whether MDT may impact on PFS. Methods: We retrospectively identified 361 patients evaluated with 68Ga-PSMA PET/CT for BCR after RP between 2016 and 2022. Patients were stratified according to PSMA PET results in negative (n=135) and positive (n=226) group. In the latter group, MDT consisted of stereotactic ablative radiation therapy (SABR) on positive spots. Clinical recurrence (CR) was defined as any new metastases detected at imaging after a first PSMA PET. Adverse pathological features (i.e. Grade Group 4-5 with = pT3a stage and/or lymph node invasion) and salvage treatments were also compared between two groups. Cox regression analyses assessed the impact of a positive PSMA PET and its interaction with MDT on CR after adjusting for PSA level at PSMA PET, number of positive spots and concomitant use of hormonal therapy. Lastly, multivariable Cox-derived Kaplan-Meier (KM) analyses depicted the time from the first PSMA PET to CR. Results: Among patients with a positive scan, 113 (31%) received MDT. Median follow-up (FU) was 30 months after PSMA PET. The 3-year CR-free survival rates were 72 vs 42% for negative vs positive PSMA PET scan since BCR. At Cox analyses, a positive PSMA PET scan was associated with 2-fold higher risk of PFS during FU as compared to a negative PSMA PET (HR 2.09, p=0.003) after adjusting for confounders. When testing interaction with use of MDT in patients with positive PSMA PET, men with positive PSMA PET not receiving MDT had higher risk of CR (HR: 2.66; p<0.001), while such risk was higher but with lesser magnitude in men with positive PSMA PET (HR: 1.74, p=0.04) receiving MDT as compared to patients with negative PSMA PET. Lastly, at the Cox derived KM, the 3-year CR-free survival rates were 73 vs 51 vs 29% in patients with negative PSMA PET vs positive PSMA PET with MDT vs positive PSMA PET without MDT, respectively. Conclusions: A negative PSMA PET scan represents a protective factor for further metastases during follow-up. Notably, in patients with positive spots, MDT significantly improved PFS, but it is still not able to compensate the protective effect of a negative PET PSMA. SOURCE OF Funding: None
