AUA 2022: The Impact Of Histological Variants On The Performance Characteristics Of 68Ga-PSMA PET/CT In The Primary And Recurrent Setting

( The 2022 Annual Meeting of the American Urological Association was host to a podium session of surgical therapies in localized prostate cancer. Dr. Simone Scuderi presented results of his group’s work evaluating the impact of histological variants on the performance of 68Ga-PSMA PET/CT in both the primary and recurrent settings.

Dr. Scuderi began his presentation by noting that çç spread in both the primary and recurrent settings, with the sensitivity of this imaging modality improving with rising PSA levels. Identification of the optimal candidate to undergo 68Ga-PSMA PET/CT at time of biochemical recurrence remains controversial, with available nomograms integrating this imaging modality in this setting having predictive abilities in the range of 64-76% (area under the curve). The answer may lie in the immunohistochemistry characteristics of the primary prostate neoplasm whereby patients with higher percentages of PSMA negative areas having increased odds of a negative imaging result. Certain histologic subtypes such as the cribriform and intraductal patterns are associated with worse prognoses. The authors thus hypothesized:

  • Could the presence of other morphologic features be associated with a different 68Ga-PSMA PET scan positivity rate in men experiencing biochemical recurrence following radical prostatectomy?

The aim was to assess the detection rates of 68Ga-PSMA PET/CT and PET/MRI in patients with mixed forms of acinar prostate cancer (aPCa) compared to patients with pure aPCa.

The authors included 277 patients with biochemical recurrence (AUA definition) treated with a robotic radical prostatectomy at a single referral center between 2015 and 2021. 73 patients were re-staged with 68Ga-PSMA PET/CT (n=55) and 68Ga-PSMA PET/MRI (n=18) at four high volume referral centers. Pathologic specimens were evaluated by two experienced uropathologists. The following mixed forms were considered:

  • Glomeruloid
  • Cribriform
  • Ductal
  • Intraductal
  • HG-PIN

Logistic regression analysis was used to evaluate the association of mixed form variability with a positive 68Ga-PSMA PET/CT finding.

Baseline patient characteristics were well-balanced between the groups, although the positive margin rate was non-significantly higher in the mixed form group (29% versus 18%, p=0.3). The most common variant mixed form was cribriform (41%).

Overall, the PSMA scan was positive in 66% of pure aPCa and 41% of mixed forms (p=0.04). In subset analyses of patients who did not undergo ADT, the positivity was 69% versus 40% in favor of the pure aPCa (p=0.04). Patients with the cribriform variant had a positivity rate of 39%.

Dr. Scuderi concluded that this study is the first attempt to assess the diagnostic accuracy of 68Ga-PSMA PET/CT and PET/MRI in patients with aPCa and other morphologic features in prostate specimens that experience biochemical recurrence after radical prostatectomy.

Presented by: Dr. Simone Scuderi, Resident Physician, Department of Urology, San Raffaele Hospital, Milan 

Written by: Rashid Sayyid, MD, MSc – Urology Chief Resident, Augusta University/Medical College of Georgia, @rksayyid on Twitter during the 2022 American Urological Association (AUA) Annual Meeting, New Orleans, LA, Fri, May 13 – Mon, May 16, 2022.