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Poster session 14

1787P - Prostate specific membrane antigen positron emission tomography (PSMA PET)-directed clinical outcomes in metastatic hormone-sensitive prostate cancer (mHSPC): Implications for the STAMPEDE2 trial design

Date

21 Oct 2023

Session

Poster session 14

Topics

Nuclear Medicine and Clinical Molecular Imaging

Tumour Site

Prostate Cancer

Presenters

Hoda Abdel-Aty

Citation

Annals of Oncology (2023) 34 (suppl_2): S954-S1000. 10.1016/S0923-7534(23)01946-4

Authors

H. Abdel-Aty1, N. Hujairi2, I. Murray2, Y. Yogeswaran3, L.R. Murphy4, N. van As5, L.C. Brown6, N.D. James1

Author affiliations

  • 1 Radiotherapy And Imaging, Institute of Cancer Research and Royal Marsden Hospital, SW3 6JB - London/GB
  • 2 Radiology And Nuclear Medicine, Royal Marsden Hospital, SM2 5PT - London/GB
  • 3 Institute Of Clinical Trials & Methodology, Medical Research Council, Clinical Trials Unit, University College London, WC1V 6LJ - London/GB
  • 4 Mrc Ctu, MRC - Medical Research Council Clinical Trials Unit - University College London (UCL), WC1V 6LJ - London/GB
  • 5 Radiotherapy And Imaging, Institute of Cancer Research and Royal Marsden Hospital, SW3 6JJ - London/GB
  • 6 Mrc Clinical Trials Unit, MRC - Medical Research Council Clinical Trials Unit - University College London (UCL), WC1V 6LJ - London/GB

Resources

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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.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

H. Abdel-Aty.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.

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