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68Ga-PSMA PET/CT in Prostate Cancer Diagnosis - Beyond the Abstract

There is a growing body of evidence supporting the use of 68Ga-labeled prostate-specific membrane antigen (68Ga-PSMA) PET/CT in prostate cancer (PCa) imaging. The modality is progressively being validated for initial staging of high-risk patients and has gained proper recommendation by the EAU during restaging after biochemical relapse.1,2 Up to now, primary diagnosis and fusion target biopsies have been dominated by multiparametric MRI (mpMRI), a highly sensitive imaging modality recommended in both biopsy-naïve patients and in the repeated biopsy setting.2 Despite these recommendations, mpMRI can still miss a good proportion of PCa foci, and more importantly up to 25% of clinically significant PCa.3 In addition, its widespread use has to face constraints related to absolute and relative contraindications to MRI itself. To overcome these limitations, 68Ga-PSMA PET/CT has been tested by our group to determine its potential role for PCa detection, starting with the selected cohort of patients having a high clinical suspicion of PCa and at least one previous negative prostate biopsy. The cohort comprised either case with negative mpMRI or contraindications to or positive but negative at target biopsy.4,5


Since our preliminary report in 2018,4 it was clear that 68Ga-PSMA PET/CT could well identify intraprostatic cancer foci with high sensitivity, and thanks to the use of semiquantitative parameters (i.e. SUVmax and SUVratio-to-background), it could provide optimal cut-off points better highlighting the presence of clinically significant PCa. The final results of our trial obtained in 97 patients, and recently published in European Urology Focus,5 not only proved the high diagnostic accuracy of PSMA PET/CT prior to fusion biopsy but allowed us to identify exactly those 25% of patients with clinically significant PCa (GS ≥ 7) missed by previous mpMRI. This could be possible after applying the optimal cut-off points for SUVmax (>5.4) and SUVratio-to-background (>2.2). The overall diagnostic accuracy reached was 90% for SUVratio.

Written by: Egesta Lopci, MD, PhD, Nuclear Medicine Department, Humanitas Clinical and Research Hospital - IRCCS, Milan, Italy

References: 

  1. Mottet, Nicolas, Joaquim Bellmunt, Michel Bolla, Erik Briers, Marcus G. Cumberbatch, Maria De Santis, Nicola Fossati et al. "EAU-ESTRO-SIOG guidelines on prostate cancer. Part 1: screening, diagnosis, and local treatment with curative intent." European urology 71, no. 4 (2017): 618-629.
  2. Mottet N, van den Bergh RCN, Briers E, et al. EAU Guidelines. https://uroweb.org/guidelines/ (2019).
  3. Ahmed, Hashim U., Ahmed El-Shater Bosaily, Louise C. Brown, Rhian Gabe, Richard Kaplan, Mahesh K. Parmar, Yolanda Collaco-Moraes et al. "Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study." The Lancet 389, no. 10071 (2017): 815-822.
  4. Lopci, Egesta, Alberto Saita, Massimo Lazzeri, Giovanni Lughezzani, Piergiuseppe Colombo, Nicolò Maria Buffi, Rodolfo Hurle et al. "68Ga-PSMA positron emission tomography/computerized tomography for primary diagnosis of prostate cancer in men with contraindications to or negative multiparametric magnetic resonance imaging: a prospective observational study." The Journal of urology 200, no. 1 (2018): 95-103.
  5. Lopci, Egesta, Giovanni Lughezzani, Angelo Castello, Alberto Saita, Piergiuseppe Colombo, Rodolfo Hurle, Roberto Peschechera et al. "Prospective Evaluation of 68Ga-labeled Prostate-specific Membrane Antigen Ligand Positron Emission Tomography/Computed Tomography in Primary Prostate Cancer Diagnosis." European Urology Focus (2020).

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