ASCO GU 2023: Patterns of Failure After Radiotherapy in Patients with Prostate Cancer Re-Staged with 18F-DCFPyL PSMA-PET: A Regional Cohort Analysis

( The 2023 GU ASCO annual meeting included a session on prostate cancer, featuring a presentation by Dr. Aruz Mesci discussing patterns of failure after radiotherapy in patients with prostate cancer re-staged with 18F-DCFPyL PSMA-PET. In Ontario, PSMA-PET is available to patients with prostate cancer who experience biochemical failure after definitive primary radiotherapy or salvage/adjuvant radiotherapy through a provincial registry study (PREP protocol). At the 2023 GU ASCO annual meeting, Dr. Mesci and colleagues reviewed patterns of PSMA-PET-detected failure after primary or salvage/adjuvant radiotherapy in cohorts of PREP-registry patients from the Local Health Integration Network (LHIN) 4 region.

The study retrospectively analyzed patients imaged with PSMA-PET in Hamilton, Ontario, Canada, after biochemical failure, following primary radiotherapy or salvage/adjuvant radiotherapy. Demographic, clinical and treatment parameters as well as PSMA-PET results were collected.

Between April 2019 and December 2021, 104 primary radiotherapy and 91 salvage/adjuvant radiotherapy patients were imaged with 18F-DCFPyL PSMA-PET. Median PSA before PSMA-PET for the two groups was 5.0 ng/mL (IQR: 3.1-8.9) and 1.3 ng/mL (IQR: 0.6-3.4):

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The percentages of prostate or prostatic bed radiotherapy alone and prostate bed + pelvic lymph node radiotherapy treatments, were prostatic bed radiotherapy in 76% of patients compared to prostate bed + pelvic lymph node radiotherapy: 24% for the primary radiotherapy group and prostatic bed radiotherapy: 49.4% vs prostate bed + pelvic lymph node radiotherapy: 50.6% for the salvage/adjuvant radiotherapy group, respectively. Rates of PSMA-PET detected local, pelvic lymph node and distant recurrence are shown as follows

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In the primary radiotherapy group, increasing the D’Amico risk category (low to high risk) was associated with lower risk for local and increased risk for pelvic and distant metastasis. Pelvic radiotherapy was associated with reduced risk for local recurrence in but not in the salvage/adjuvant radiotherapy group:

pelvic recurrance rate.jpg

Dr. Mesci concluded his presentation discussing patterns of failure after radiotherapy in patients with prostate cancer re-staged with 18F-DCFPyL PSMA-PET with the following take-home messages:

  • In this cohort of patients, PSMA-PET detected a considerable risk for local recurrence in patients treated with primary radiotherapy
  • A high number of patients are detected with pelvic-only disease recurrence, but pelvic radiotherapy seems to be associated with reduction in this risk only in the primary radiotherapy population
  • Studies with PSMA-PET at baseline, before primary radiotherapy or salvage/adjuvant radiotherapy, may help discern better patients that would benefit from pelvic and systemic therapy

Presented by: Aruz Mesci, MD, FRCPC, University of Toronto and Princess Margaret Cancer Centre, Toronto, ON, Canada

Co-Authors: Sneha Mukherjee, Mohammad Gouran-Savadkoohi, Anil Kapoor, Glenn Bauman, Himu Lukka, Ian S. Dayes, Kara Schnarr, Mira Goldberg, Kimmen Quan, Katherine A. Zukotynski, Theodoros Tsakiridis

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 2023 Genitourinary (GU) American Society of Clinical Oncology (ASCO) Annual Meeting, San Francisco, Thurs, Feb 16 – Sat, Feb 18, 2023.