The aim of this retrospective study was to assess the prognostic value of parameters extracted from 18FDG PET/CT and 68Ga-PSMA PET in the initial workup and follow-up of patients treated with 177Lu-PSMA in mCRPC.

Prostate-specific membrane antigen (PSMA) is expressed in most metastatic castration-resistant prostate cancer (mCRPC) cells. In response to this finding, a vectorized internal radiotherapy (VIR) therapy was developed, lutetium 177-labeled PSMA, 177Lu-PSMA. Clinical trials have demonstrated its efficacy in men with metastatic castration-resistant prostate cancer . The number of patients treated in nuclear medicine departments has increased considerably in recent years, notably with the Food and Drug Administration's (FDA) and the European Medicines Agency's (EMA) approval of this treatment (177Lu-PSMA-617, Pluvicto®) in the setting of progressive mCRPC after at least one line of 2nd-generation hormone therapy and one line of taxane chemotherapy.

Patients eligible for treatment benefit from pre-therapy 68Ga-PSMA positron emission tomography (PET/CT) to assess PSMA expression by cancer cells, but 18FDG PET/CT, although mentioned in the EANM guidelines, is not routinely performed. For treatment follow-up of prostate cancer patients, the PCWG3 (prostate cancer working group 3) currently recommends conventional imaging (CT scan and bone scan) (4) and makes no mention of metabolic imaging, even though some lesions are not detectable with conventional imaging. In addition, one study reported that a high metabolic volume 18FDG PET/CT scan as part of the pre-therapy work-up for mCRPC prior to the introduction of 177Lu-PSMA or Cabazitaxel therapy was associated with a poorer response to treatment.

The aim of this retrospective study was to assess the prognostic value of parameters extracted from 18FDG PET/CT and 68Ga-PSMA PET in the initial work-up and follow-up of patients treated with 177Lu-PSMA in mCRPC.

Inclusion Criteria:

• Patients treated with 177Lu-PSMA for castration-resistant prostate cancer at Nancy University Hospital
• Patients with 68Ga-PSMA and 18FDG PET scans as part of the initial workup and treatment follow-up

Exclusion Criteria:

• Patients who did not give their consent to use their data retrospectively

Patients treated with 177Lu-PSMA for castration-resistant prostate cancer at the CHRU de Nancy and who benefited from 68Ga-PSMA and 18FDG PET scans as part of the initial workup and treatment follow-up.