ESMO Congress 2023 | OncologyPRO

Abstract 1787P

Background

The potential for PSMA PET-directed treatment decisions to improve outcomes in mHSPC remains unknown. We explored first response and progression/relapse patterns in newly diagnosed PSMA PET-detected mHSPC and correlated PET-directed staging with clinical outcomes.

Methods

184 patients with baseline PSMA PET were retrospectively reviewed. Patients were sub-grouped into oligometastatic disease (OMD) and polymetastatic disease (PMD) utilising the STAMPEDE2 trial definition. Data on patient demographics, treatment, and imaging findings were collected. Treatment response was assessed using PSA nadir and radiological imaging at six months from PSA nadir. Disease progression/relapse was assessed using PCWG3, RECIST 1.1 and PERCIST 1.0 criteria. Kaplan Meier method estimated median time to radiographic progression-free survival (rPFS).

Results

Median age was 69 years. All patients had androgen deprivation therapy. 161/184 (88%) had additional systemic therapies. 99/184 (54%) had OMD and 85/184 (46%) had PMD. Prostate radiotherapy was given in 76/99 (77%) OMD patients and 47/85 (55%) PMD patients. Median time to PSA nadir in OMD and PMD was 10 months (range 1 to 29) and 8 months (range 1 to 36), respectively. Response images were available in 35/99 (35%) OMD patients and 39/85 (46%) PMD patients. Median time to radiological response in OMD and PMD was 10 months (range 2 to 58) and 9 months (range 2 to 36), respectively. Radiological progression in OMD most frequently occurred with new sites of disease (73%). Median rPFS was 53 months (95% CI 40, undefined) in OMD patients and 35 months (95% CI 22, 43) in PMD patients. Table: 1787P

Radiological response and progression/relapse in OMD and PMD

	OMD (N= 99)	PMD (N= 85)
Radiological response	n= 35 (35%)	n= 39 (46%)
Complete Response	12 (34%)	7 (18%)
Partial Response	21 (60%)	29 (74%)
Stable Disease	1 (3%)	2 (5%)
Not evaluable	1 (3%)	1 (3%)
Site of Radiological progression/relapse compared with baseline disease	n= 22 (22%)	n= 37 (43%)
Same sites	5 (23%)	18 (49%)
Different sites	10 (45%)	9 (24%)
Mixed sites	6 (27%)	10 (27%)
Not evaluable	1 (5%)	0 (0%)

Conclusions

PSMA PET-guided outcomes were similar to series with conventional staging, suggesting PET-directed therapy choices might not significantly influence time to progression. This will be further investigated in the forthcoming STAMPEDE2 trial.