Additionally, small lymph node metastases may be missed given that the spatial resolution of PET is ~5 mm. In this retrospective cohort study, Dr. Grogg and colleagues assessed the diagnostic accuracy of PSMA-PET-CT before radical prostatectomy.
Men treated with radical prostatectomy and pelvic lymph node dissection with preoperative 68Ga-PSMA-11-PET/CT and no visible PSMA bone lesions were reviewed. The composite endpoint was defined as either any:
- Histologically confirmed lymph node involvement in the pelvic lymph node dissection specimen (pN1)
- Elevated/recurring PSA
- Further cancer treatment after radical prostatectomy
Among 150 men with a median age of 66 years and a median preoperative PSA of 8.8 ng/ml, 61 (41%) had a biopsy-proven Gleason Score of 7 and 89 (59%) a Gleason Score of 8-10. A median of 22 (IQR 17-28) lymph nodes was resected and pN1 was detected in 39 men (26%). Elevated/recurring PSA was observed in 46 (31%) men after a median follow-up of 1 year. The composite endpoint of pN1 or elevated/recurring PSA was observed in 56 (37%) men. The sensitivity and specificity of PSMA-PET-CT were 0.27 (95% CI 0.16-0.40) and 0.97 (95% CI 0.91-0.99), respectively. In this cohort, this diagnostic accuracy resulted in a positive and negative predictive value of 0.83 (95% CI 0.59-0.96) and 0.69 (95% CI 0.60-0.77), respectively. In the 18 men with positive pelvic lymph nodes on PSMA-PET-CT and a median follow-up time of 7.5 months (IQR 3-16), 14 showed pN1 disease, 1 pN0 with a biochemical recurrence, and 3 pN0 without biochemical recurrence.
Dr. Grogg concluded his presentation with the following take-home messages:
- This data suggests that in men with intermediate and high-risk prostate cancer staged with PSMA-PET-CT before radical prostatectomy, 1 out of 5 men with PSMA-PET-CT suspicious nodes may be staged as pN0 and do not need further treatment at least during short-term follow-up
- Similarly, a negative PSMA-PET-CT does not rule out lymph node involvement, as 1 out of 3 men with a negative scan had pN1 disease or needed further treatment
- Men with positive lymph nodes on PSMA-PET-CT should not be withheld curative treatment and further studies should use strong endpoints including histopathology and clinical follow-up
Presented By: Josias B. Grogg, MD, University of Zurich, Dept. of Urology, Zurich, Switzerland
Written By: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2021 European Association of Urology, EAU 2021- Virtual Meeting, July 8-12, 2021.