EAU 2021: Long-Term Validation on the Impact of PSMA-PET on Metastasis-Free Survival in a Large Salvage Radiotherapy Cohort

(UroToday.com) Dr. Christoph Wurnschimmel discussed long-term validation on the impact of PSMA-PET on metastasis-free survival (MFS) in a large salvage radiotherapy cohort at the European Association of Urology (EAU) 2021 annual meeting’s detection of recurrence and salvage treatment options after primary treatment of prostate cancer session. Earlier studies focusing on the impact of PSMA-PET imaging for treatment planning prior to salvage radiotherapy for PSA recurrence after radical prostatectomy suggested a high response rate in PSMA negative findings as opposed to PSMA positive findings. However, most available literature either only reported short-term follow-up or did not address long-term MFS. The objective of this study was to provide a large and contemporary report that provides 5-year MFS rates after salvage radiotherapy by PSMA PET results.


This study retrospectively identified all patients who were treated with radical prostatectomy for localized prostate cancer at the University Hospital Hamburg-Eppendorf, Martini-Klinik Prostate Cancer Center and subsequently received salvage radiotherapy for PSA recurrence between 2012-2018. Among these patients, Dr. Wurnschimmel and colleagues identified individuals who received PSMA PET prior to salvage radiotherapy and stratified the analyses into PSMA positive versus PSMA negative versus no PSMA PET. Additionally, 4:1 propensity score matching for clinical and cancer characteristics as well as for concomitant androgen deprivation therapy (ADT) was performed, first between “no PSMA-PET” versus “PSMA positive” and second between “no PSMA-PET” versus “PSMA negative”. Univariable Kaplan-Meier analyses displayed five-year MFS. Cox proportional hazards models calculated the independent association of PSMA findings on MFS. All tests were two-sided with a level of significance set at p<0.05.

 Overall, among 1,784 patients (100%), 1,585 patients received “no PSMA PET” (88.8%), 123 exhibited “negative PSMA PET” (6.9%), and 76 exhibited “positive PSMA PET” (4.3%) prior to salvage radiotherapy. Median follow-up was 61.2 months and time to biochemical recurrence after radical prostatectomy was 20.9 ng/ml, 24.2 ng/ml, and 17.4 ng/ml for “no PSMA PET”, “negative PSMA PET” and “positive PSMA PET”, respectively (p=0.04). Median PSA at recurrence was 0.2 ng/ml, 0.2 ng/ml, and 0.3 ng/ml for “no PSMA PET”, “negative PSMA PET” and “positive PSMA PET”, respectively (p=0.1). Rate of salvage ADT was highest in “positive PSMA PET” (57.9%), followed by “negative PSMA PET” (47.2%) and “no PSMA PET” (25.6%), respectively.  In multivariable Cox regression analyses, both “negative” and “positive PSMA PET” were independently associated with worse MFS compared to “no PSMA PET” (HR 2.38, CI 1.12-5.04 for negative PSMA PET, p=0.02; HR 24.55, CI 15.60-38.63 for positive PSMA PET, p<0.0001). After 4:1 propensity score matching, the 5-year MFS “no PSMA PET” versus “negative PSMA PET” was 94.5% versus 90.6% (p=0.2), and the 5-year MFS “no PSMA PET” versus “positive PSMA PET” was 92.7% versus 38.2% (p<0.001):

 

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Dr. Wurnschimmel concluded this presentation with the following take-home messages:

  • “Positive PSMA PET” vastly differs from “negative PSMA PET” and “no PSMA PET”
  • “Positive PSMA PET” has high rates of MFS despite salvage radiotherapy, which raises the questions if the treatment approach for these individuals needs to be improved
  • Several limitations of this study include (i) the small sample size of positive PSMA PET patients, (ii) no standardized imaging routines during follow-up, and (iii) no explicit radiological information on disease burden

Presented by: Christoph Wurnschimmel, MD, University Hospital Hamburg-Eppendorf, Martini-Klinik Prostate Cancer Center, Hamburg, Germany

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.

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