Moving 177Lu-PSMA-617 earlier slows hormone-sensitive prostate cancer in PSMAddition

PSMAddition, a phase 3 trial, tested whether adding the radioligand [177Lu]Lu-PSMA-617 to standard hormonal treatment helps men whose prostate cancer has spread but has not yet become resistant to hormone therapy — and it did, cutting the risk of radiographic progression or death by 28% (hazard ratio 0.72; 95% CI 0.58 to 0.90; p=0.0021) [s1]. The benefit is real but incremental: median radiographic progression-free survival was not reached in either group, the absolute difference in events was six percentage points, and it came with more toxicity, so the drug's place at this earlier stage of disease is not yet settled [s1].

The drug, marketed as Pluvicto, is a targeted radiation therapy: it homes to prostate-specific membrane antigen (PSMA), a protein studded on the surface of most prostate-cancer cells, and delivers a short-range beta-particle payload to the tumour and its immediate surroundings [s2]. It is already approved for late-stage, castration-resistant disease that has progressed after an androgen-receptor pathway inhibitor and taxane chemotherapy, on the strength of the VISION trial, where it extended imaging-based progression-free survival to a median of 8.7 months versus 3.4 months with standard care alone [s2]. PSMAddition asks the natural next question: does moving it forward, into newly diagnosed metastatic hormone-sensitive disease, pay off?

What the trial did

PSMAddition enrolled 1,144 men across 169 sites in 20 countries and randomly assigned them 1:1 — 572 to each arm [s1]. Everyone received the current standard of care, androgen-deprivation therapy plus an androgen-receptor pathway inhibitor; one group also received [177Lu]Lu-PSMA-617 at 7.4 GBq every six weeks for up to six cycles [s1]. The population was typical of newly diagnosed metastatic disease: median age 68.0 years, half (50%) with cancer that was metastatic at first diagnosis, and 68% with high-volume disease [s1]. The primary endpoint was radiographic progression-free survival, read centrally, and men in the control arm whose disease progressed could cross over to the radioligand [s1].

The result reported here is a second interim analysis, with a data cutoff of 13 January 2025; the trial is ongoing [s1]. That timing matters for how much weight the numbers can bear.

What it found

At the interim analysis, 139 of 572 men (24%) in the radioligand arm and 172 of 572 (30%) in the control arm had radiographic progression or death — the 28% relative reduction that met the primary endpoint (HR 0.72; 95% CI 0.58 to 0.90; p=0.0021) [s1]. Because median progression-free survival had not been reached in either arm, the trial has established that the curves separate in favour of the radioligand without yet fixing by how many months [s1].

The cost side was measurable. Grade 3 or worse adverse events occurred in 286 of 564 treated men (51%) in the radioligand arm versus 243 of 565 (43%) with standard care alone, and serious adverse events in 32% versus 29% [s1]. The signature toxicity was dry mouth, a known consequence of PSMA-directed therapy because salivary glands also express the target: it affected 258 men (46%) on the radioligand against 21 (4%) in the control arm, though all cases were grade 1 or 2 and none were serious [s1].

How to read it

Three caveats frame an honest verdict. First, "not reached" cuts both ways — the effect is convincing at the level of relative risk, but the absolute survival gain and the durability of it will only be legible with longer follow-up. Second, this is an add-on to an already intensified backbone; the comparator was not weak standard care but ADT plus a modern hormonal agent, so the 28% is a marginal benefit stacked on top of good treatment, not a stand-alone effect [s1]. Third, the trial was funded by Novartis, which makes the drug; the reporting journal is independent and the endpoint was centrally assessed, but the framing of a positive interim analysis is worth keeping in view.

What the trial does not answer is where a fourth treatment modality fits against the other intensification already available in this setting — notably the addition of docetaxel chemotherapy — because PSMAddition did not test that comparison [s1]. Nor does it speak to overall survival, which remains immature.

Why it matters

Radioligand therapy has spent years migrating from a last-resort option toward the front of the treatment line, and PSMAddition is the first phase 3 evidence that the migration improves a hard endpoint in hormone-sensitive disease [s1][s2]. For a cancer where PSMA-targeted PET imaging is already reshaping how metastases are found, a matching therapy that uses the same target is a coherent next step. The practical brake is access: the strategy depends on PSMA-PET to select patients and on the radiopharmacy infrastructure to deliver the isotope, both unevenly distributed.

The same PSMA target that makes this therapy possible also underlies newer diagnostic and treatment strategies in prostate cancer, including the genetic testing that identifies men who benefit from a different class of drug — the PARP inhibitors used in BRCA-mutated prostate cancer — and it sits alongside the older hormonal backbone whose side-effects are themselves an active research question.

What to watch

The decisive numbers are still ahead: mature overall-survival data, a median progression-free survival once the curves mature, and whether regulators extend the label from castration-resistant to hormone-sensitive disease on an interim progression endpoint. Also unresolved is sequencing — whether using the radioligand early leaves an effective option for later, or spends it — since men in this trial received it before, not after, resistance emerged [s1].

This article describes research and regulatory developments and is not medical advice. Treatment decisions are for patients and their treating clinicians.

Sources

• [177Lu]Lu-PSMA-617 in patients with PSMA-positive metastatic androgen pathway modulator-naive/sensitive prostate cancer (PSMAddition) — The Lancet, online 6 August 2026
• Lutetium-177–PSMA-617 for Metastatic Castration-Resistant Prostate Cancer (VISION) — New England Journal of Medicine, online 23 June 2021