AUA 2022: 68 Ga-PSMA PET/CT for Preoperative Lymph Node Staging of High Risk Prostate Cancer

(UroToday.com) The 2022 Annual Meeting of the American Urological Association was host to a podium session on surgical therapies in localized prostate cancer. Dr. Maximilian Schmautz presented the results of his group’s study evaluating the role of 68Ga-PSMA PET/CT for the preoperative lymph node (LN) staging of high risk prostate cancer.

Dr. Schmautz began his presentation by highlighting that current guidelines recommend cross sectional imaging during the work up of both unfavorable intermediate and high-risk prostate cancer. The EAU guidelines now acknowledge that PSMA PET/CT is more accurate for staging than CT and bone scan but to date no outcome data exists to inform subsequent management.

The objective of this study was to evaluate the role of 68Ga-PSMA PET/CT in detecting pelvic lymph node metastases in newly diagnosed, treatment-naïve high risk prostate cancer patients prior to radical prostatectomy and extended pelvic lymphadenectomy. This was a retrospective analysis of 165 men with newly diagnosed high risk PCa (ISUP Grade 4/5, PSA>20 ng/ml, or >=cT3a). All patients were diagnosed using mpMRI guidance. PSMA imaging was performed 1 week prior to surgery (radical prostatectomy plus extended pelvic lymphadenectomy). Patients with prior pelvic treatment, ADT or distant metastases were excluded.

The median patient age was 66.7 years and PSA 24.5 ng/ml (6.7-185,000). A median of 21.5 LNs were harvested per patient (range: 15-45).

  • A total of 41.2% of patients had pathologic lymph node involvement, of which 63.2% were positive on PSMA-PET/CT
  • 97/165 (58.8%) patients had pN0 disease of whom 95.9% had a negative PSMA PE/CT.
  • 47 patients had a positive PSMA PET/CT, of which 85.1% demonstrated pathologic LN involvement.
  • 118 patients had a negative PSMA PET/CT of which 93 (78.8%) were true negative.
  • Sensitivity was 63.2%, specificity was 97.0%, and positive and negative predictive values were 93.5% and 78.8%, respectively.

3564 lymph nodes were resected of which 149 (4.2%) were positive. On a per lymph node base, sensitivity and specificity were 40.4% and 94.5%, resp; positive and negative predictive values were 59.1% and 97.3%.

The size of positive LNs with a negative PET/CT scan was significantly smaller (2-4 mm) compared to those with positive imaging and limited by spatial resolution.

The authors concluded:

  • PSMA PET/CT scan is superior to standard preoperative imaging
  • Positive activity in preoperative PET/CT scan is highly correlated with histopathologic findings in metastases in up to 90% of patients and should lead to extended pelvic LN dissection
  • 21% of LN positive patients could not be detected by pre-operative PSMA imaging, thus there is a need for further innovations to improve the detection of small lesions

 

Presented by: Dr. Maximilian Schmautz, MD, University of Cologne, Cologne, Germany

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. 

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