2. UroToday Home
  3. Conference Highlights
  4. Society of Urologic Oncology (SUO) 21st Annual Meeting
  5. SUO 2020 GU Malignancies Non-Prostate

Society of Urologic Oncology (SUO) 21st Annual Meeting

SUO 2020: Unmet Needs in Prostate Cancer and How Novel PET Fills Them

(UroToday.com) In a point and counterpoint format at the 2020 Society of Urologic Oncology (SUO) virtual meeting discussing whether PSMA PET-CT is ready for prime-time use, Dr. Tanya Dorff took the “pro” point approach that prostate-specific membrane antigen (PSMA) PET-CT is ready for prime-time use and may fill an unmet need in the treatment of prostate cancer. These unmet needs include high-risk localized disease, biochemical recurrence, oligometastatic, and mCRPC as summarized in the following figure:



SUO_Tanya_Dorff_1.png



The proPSMA trial from Australia found that PSMA PET-CT had a 27% absolute greater area under the curve (AUC) for accuracy compared to conventional imaging (95% CI 23-31): 92% (95% CI 88-95%) vs. 65% (60-69%).1 Conventional imaging had both a lower sensitivity (38% vs. 85%) and also a lower specificity (91% vs. 98%). When stratified by disease site/burden of disease, we gain additional important information:

SUO_Tanya_Dorff_2.png



According to Dr. Dorff, there are clinical applications to be gained from this data including (i) adding/intensifying systematic treatment if there is locoregional metastatic disease, and (ii) expanding the surgical lymph node dissection and/or radiation fields.

Data from Calais et al.2 also suggests that we may be able to select patients that would benefit from salvation radiotherapy. In this prospective, single-center, open-label, single-arm comparative study of 50 patients, detection rates were significantly lower with 18F-fluciclovine PET-CT (13 [26%; 95% CI 15-40] of 50 men) than with PSMA PET-CT (28 [56%; 41-70] of 50 men), with an OR of 4.8 (95% CI 1.6-19.2; p=0.0026) at the patient level. Stratified by PSA category after biochemical recurrence, PSA 0.2-0.5 ng/mL had a 46% detection rate.

PSMA PET/CT may also have the utility of selecting oligometastatic patients for therapy. Several phase II trials have suggested that metastasis directed therapy may be beneficial. In the STOMP trial,3 Ost and colleagues randomly assigned 62 patients to either surveillance or MDT of all detected lesions (surgery or stereotactic body radiotherapy), with a primary endpoint of ADT-free survival. At a median follow-up time of 3 years (IQR 2.3-3.75 years), the median ADT-free survival was 13 months (80% CI 12 to 17 months) for the surveillance group and 21 months (80% CI 14 to 29 months) for the MDT group (HR 0.60, 80% CI 0.40 to 0.90; log-rank p = 0.11). In the single-arm prospective POPSTAR trial, 33 consecutive patients received SABR to a total of 50 oligometastases and were followed for two years.4 The 1 and 2-year local-PFS was 97% (95% CI 91-100) and 93% (95% CI 84-100), and distant PFS was 58% (95% CI: 43-77) and 39% (95% CI: 25-60), respectively. Among those not on ADT (n=22), the 2-year freedom from ADT rate was 48%. The SABR-COMET.5 trial randomized 99 patients (1:2) to receive either palliative standard of care treatments alone (control group) or standard of care plus stereotactic body radiotherapy to all metastatic lesions (SABR group). Over a median follow-up was 25 months (IQR 19-54) in the control group versus 26 months (23-37) in the SABR group, median overall survival was 28 months (95% CI 19-33) in the control group versus 41 months (26-not reached) in the SABR group (HR 0.57, 95% CI 0.30-1.10; p=0.090). 

Dr. Dorff concluded her presentation for “pro” PET PSMA in prostate cancer with the following take-home messages:
  • We do need more data, but we can rationally apply PET in the interim for select situations
  • Since we have the accuracy, if we see extraprostatic disease in high-risk localized patients, this should impact our plan
  • Since the sensitivity is not perfect, a negative PET for BCR should mean proceed to salvage radiation therapy (but positivity outside the prostate bed should change the treatment plan)
  • The sensitivity is much better than standard imaging, thus if you are going to treat oligometastatic disease, use the most sensitive test to define the disease burden

Presented by: Tanya B. Dorff, MD, Associate Clinical Professor, Department of Medical Oncology & Therapeutics Research, Head of the Genitourinary Cancers Program, City of Hope Comprehensive Cancer Center, Duarte, CA

Written by: Zachary Klaassen, MD, MSc – Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia Twitter: @zklaassen_md at the 21st Annual Meeting of the Society of Urologic Oncology (SUO), December 3-5, Virtual Conference

References:
  1. Hofman MS, Lawrentschuk N, Francis, RJ, et al. Prostate-specific membrane antigen PET-CT in patients with high-risk prostate cancer before curative-intent surgery or radiotherapy (proPSMA): A prospective, randomized, multicentre study. Lancet 2020 Apr 11;395(10231):1208-1216.
  2. Calais J, Ceci F, Eiber M, et al. 18F-fluciclovine PET-CT and 68Ga-PSMA-11 PET-CT in patients with early biochemical recurrence after prostatectomy: A prospective, single-centre, single-arm, comparative trial. Lancet Oncol 2019 Sep;20(9):1286-1294.
  3. Ost P, Reynders D, Decaestecker K, et al. Surveillance of Metastasis-Directed Therapy for Oligometastatic Prostate Cancer Recurrence: A Prospective, Randomized, Multicenter Phase II Trial. J Clin Oncol 2018 Feb 10;36(5):446-453.
  4. Siva S, Bressel M, Murphy DG, et al. Stereotactic Ablative Body Radiotherapy (SABR) for Oligometastatic Prostate Cancer: A Prospective Clinical Trial. Eur Urol 2018 Oct;74(4):455-462.
  5. Palma DA, Olson R, Harrow S, et al. Stereotactic ablative radiotherapy versus standard of care palliative treatment in patients with oligometastatic cancers (SABR-COMET): A randomized, phase 2, open-label trial. 2019 May 18;393(10185):2051-2058.

Related Content:

Read the Opposing Debate: SUO 2020: Impact of PSMA Scans on Clinical Management - PSMA PET-CT is Not Ready for Prime-Time Use