RETROSPECTIVE STUDY

Hadaschik et al (2023)¹ conducted a retrospective study to assess the prognostic value  of prostate-specific membrane antigen ligand positron emission tomography (PSMA-PE/T) for patients with nonmetastatic castration-resistant prostate cancer (nmCRPC) in terms of overall survival (OS), new metastases-free survival (nMFS), and implemented lines of treatment after PSMA-PET.

Study Design/Methods

• Retrospective, international, multicenter study
• Patients with nmCRPC from a previous study² were followed up for 4-9 years after PSMA-PET imaging.
• Databases from 6 high-volume PET centers were screened to identify patients with nmCRPC characteristics that were similar to those in the SPARTAN³ trial. The characteristics screened for included the following:
  • Prostate-specific antigen (PSA) doubling time <10 months and/or Gleason score ≥8 (International Society of Urological Pathology [ISUP] grade group ≥4)
  • No pelvic nodes ≥2 cm in the short axis
  • No distant metastases on conventional imaging
• The PSMA-PET images were interpreted by 2 central readers who were aware of each patient’s most recent PSA value and prior treatments but were blinded to other imaging findings and clinical data. The images were also interpreted by 1 unblinded local reader.
• The qPSMA software was used for whole-body PSMA-positive tumor volume segmentation.
• Primary endpoint: OS
• Secondary endpoints: nMFS (time from PSMA-PET to any-cause death or new metastases detected using any imaging method, including PSMA-PET) and first- and second-line treatment implementation after PSMA-PET

Results

Patient Characteristics

• The full cohort included 200 patients followed for a median of 74 months.

OS

• Fifty-six (28%) patients had OS events.
• The median OS was 74 months for the full cohort. In comparison, the median OS in SPARTAN was 74 months for the ERLEADA group.⁴
  • In patients stratified by initial pelvic node (pN) status, the median OS was not reached (NR) for prostate cancer with unknown status/without pelvic lymph node involvement (pNx/0) and 55 months (95% CI [confidence interval], 46-64; P=0.010) for prostate cancer with 1 pelvic lymph node involved (pN1).
  • Based on the number of extrapelvic metastases detected by PSMA-PET, the median OS was NR for <5 distant lesions and 61 months (95% CI, 37-85; P=0.024) for ≥5 distant lesions.
  • Based on PSMA-PET avidity, the median OS was NR for lower SUV_max (maximum standardized uptake value) and 63 months (95% CI, 51-75; P=0.035) for SUV_max ≥8.4.

nMFS

• Eighty-three (42%) patients had nMFS events.
• The median nMFS was 59 months (95% CI, 49-69) for the entire cohort.
  • In patients stratified by number of extrapelvic metastases detected by PSMA-PET, the median nMFS was 60 months (95% CI, 47-73) for <5 distant lesions and 38 months (95% CI, 29-47; P=0.018) for ≥5 distant lesions.

Implemented Lines of Treatment

• Patients (n=158) were evaluated for first- and second-line treatment implementation after PSMA-PET in the following 4 disease groups:
  • No disease or local recurrence (miT0N0M0 or TrN0M0)
  • Locoregional metastatic disease (miT0N1M0 or TrN1M0)
  • Distant metastatic disease (miT0N0M1 or TrN0M1)
  • Locoregional and distant metastasic disease (miT0N1M1 or TrN1M1)
• Androgen deprivation therapy (ADT) was continued for patients in all disease groups.
• Locoregional and targeted therapies were the most common treatments in patients with no/local disease (miTxN0M0) or locoregional disease (miTxN1M0), per PSMA-PET.
• Intensification of systemic treatment (ie, androgen receptor signaling inhibitor [ARSI], poly-adenosine diphosphate ribose polymerase [PARP] inhibitor, chemotherapy, radioligand therapy, and others) was required most frequently in patients with distantonly (miM1) or combined locoregional and distant disease (miN1M1).

Safety results were not reported.