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Curative-intent Metastasis-directed Therapies for Molecularly-defined Oligorecurrent Prostate Cancer: A Prospective Phase II Trial Testing the Oligometastasis Hypothesis

  • Rachel M. Glicksman,
  • Ur Metser,
  • Douglass Vines,
  • John Valliant,
  • Zhihui Liu,
  • Peter W. Chung,
  • Robert G. Bristow,
  • Antonio Finelli,
  • Robert Hamilton,
  • Neil E. Fleshner,
  • Nathan Perlis,
  • Alexandre R. Zlotta,
  • David Green,
  • Andrew Bayley,
  • Joelle Helou,
  • Srinivas Raman,
  • Girish Kulkarni,
  • Charles Catton,
  • Tony Lam,
  • Rosanna Chan,
  • Padraig Warde,
  • Mary Gospodarowicz,
  • David A. Jaffray,
  • Alejandro Berlin

Background

The hypothesis of a curable oligometastatic prostate cancer (PCa) state remains to be clinically-proven. Conventional imaging often fails to localize early recurrences, hampering the potential for radical approaches.

Objective

We hypothesize that prostate-specific membrane antigen (PSMA)-targeted PET-MR/CT allows for earlier detection and localization of oligorecurrent-PCa, unveiling a molecularly-defined state amenable to curative-intent metastasis-directed treatment (MDT).

Design/setting/participants

Single-institution single-arm phase-two study. Patients with rising PSA (0.4-3.0 ng/mL) after maximal local therapy (radical prostatectomy and post-operative radiotherapy), negative conventional staging, and no prior salvage hormonal therapy (HT) were eligible.

Interventions

All patients underwent [18F]DCFPyL PET-MR/CT. Patients with molecularly-defined oligorecurrent-PCa had MDT (stereotactic ablative body radiotherapy [SABR] or surgery) without HT.

Outcome measurements/statistical analysis

Primary endpoint was biochemical response (complete, i.e. biochemical ‘no evidence of disease’ [bNED], or partial response [100% or ≥50% PSA decline from baseline, respectively]) after MDT. Simon’s two-stage design was employed (null and alternate hypotheses <5% and >20% response rate, respectively), with α and β of 0.1.

Results

Seventy-two patients were enrolled (May/2017-July/2019). Thirty-eight (53%) had PSMA-detected oligorecurrent-PCa amenable for MDT. Thirty-seven (51%) agreed to MDT: 10 and 27 underwent surgery and SABR, respectively. Median follow-up was 15.9 months (IQR 9.8-19.1). Of patients receiving MDT, the overall response rate was 60%, including 22% rendered bNED. One (2.7%) grade 3 toxicity (intra-operative ureteric injury) was observed.

Conclusions

PSMA-defined oligorecurrent-PCa can be rendered bNED, a necessary step towards cure, in 1 of 5 patients receiving MDT alone. Randomized trials are justified to determine if MDT +/− systemic agents can expand the curative therapeutic armamentarium for PCa.