PSMA-guided radiotherapy: no overall win, but a signal in high-risk disease

Design

Phase 2, two-centre, open-label randomised controlled trial

Population

253 prostate cancer patients planned for standard-of-care radiotherapy (four strata)

Primary outcome

Failure-free survival from radiotherapy completion

Effect

5-year failure-free survival 66% vs 62% (hazard ratio 0.80, not significant); biochemical control favoured intensification in high-risk and post-prostatectomy strata

PSMA-PET finds prostate cancer deposits that conventional imaging misses, prompting clinicians to escalate radiotherapy to those sites. Whether that changes outcomes was the question of this phase 2, two-centre randomised trial of 253 patients across four strata (post-prostatectomy salvage, high-risk, oligometastatic, and post-radiotherapy salvage).

The primary endpoint, failure-free survival at five years, was not met: 66% with PSMA-guided radiotherapy versus 62% with standard of care (hazard ratio 0.80, not significant). But freedom from biochemical progression favoured the intensified arm, 72% versus 65% overall, and more strongly in high-risk disease (81% vs 66%) and the post-prostatectomy stratum (80% vs 68%); a combined high-risk and post-prostatectomy analysis gave a subdistribution hazard ratio of 0.54. Only one grade 3 or higher event was possibly related to dose escalation.

For practice this is encouraging but not yet decisive. It does not establish PSMA-guided escalation as standard, but it does identify the high-risk and post-prostatectomy patients most likely to benefit, which is exactly who the definitive phase 3 PATRON trial is testing.

• Phase 2 trial of 253 patients randomised to PSMA-guided radiotherapy intensification versus standard of care.
• The primary five-year failure-free survival endpoint was not met (66% vs 62%, hazard ratio 0.80, not significant).
• Freedom from biochemical progression favoured intensification overall (72% vs 65%) and in high-risk and post-prostatectomy strata.
• The combined high-risk and post-prostatectomy effect was a subdistribution hazard ratio of 0.54.
• Await the phase 3 PATRON trial before adopting PSMA-guided escalation as standard.

Why it matters

It stops PSMA-guided dose escalation being adopted wholesale on imaging alone, while pointing to the specific patients in whom it may genuinely help.

Don't overread it

The prespecified primary endpoint was negative; the favourable results are secondary and subgroup analyses in a phase 2 trial, not proof that escalation improves outcomes.

The statistics, in plain English

A non-significant primary endpoint means the trial did not prove its main hypothesis, so the biochemical-progression benefits are secondary and subgroup findings, which generate hypotheses rather than confirm them; the combined-subgroup interval (0.32 to 0.91) was from a post-hoc analysis.

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