What does PSMA-targeted radiation add to standard hormone therapy?
Yes. Adding a targeted radiation drug to standard hormone therapy cut the risk of prostate cancer growing or of death by about 28 percent (hazard ratio 0.72). In this phase 3 trial of 1,144 men, the treatment met its main goal.
Most men with prostate cancer that has spread start on androgen deprivation therapy plus a second drug called an androgen receptor pathway inhibitor. Both work by shutting down testosterone, the hormone that feeds prostate cancer. That combination is the current standard of care, and it is given until the cancer starts growing again.
The PSMAddition trial tested whether a very different kind of drug could be layered on top. [177Lu]Lu-PSMA-617 is a radioligand. It is a molecule that seeks out a protein called PSMA sitting on the surface of prostate cancer cells, latches onto it, and delivers a small dose of radiation right there. Healthy tissue gets much less exposure than it would from a broad beam of radiation. Only men whose scans showed PSMA on their tumors were allowed in, so the drug had a target to find.
What the Data Show
At this second interim look, 139 of 572 men (24 percent) on the radioligand had their cancer grow on imaging or had died, compared with 172 of 572 men (30 percent) on hormone therapy alone. That works out to 33 fewer men out of 572, or about 6 fewer per 100 over the follow-up so far. Put another way, about 17 men would need the added treatment for one of them to avoid progression or death during this window.
The relative reduction was 28 percent (hazard ratio 0.72, 95 percent confidence interval 0.58 to 0.90). The true benefit is very likely somewhere between a 10 percent and a 42 percent reduction in risk. There was about a 2 in 1,000 chance that a result this large came from luck alone (p = 0.0021). Median time to progression had not been reached in either group, meaning more than half the men in both arms were still progression free when the data were locked.
Dr. Kumar’s Take
Radioligand therapy has been a late-stage option, something we reach for after hormone drugs and chemotherapy have stopped working. Moving it to the front of the line, alongside first treatment, is a real shift in how this disease might be managed.
The size of the effect is solid but not dramatic, and it is measured on scans rather than on how long men live. Overall survival data are not mature yet in this analysis, and that is the number that matters most to the man sitting across from me. Scan-based progression and survival do not always track together in prostate cancer.
The dry mouth number also deserves attention. Nearly half of the men on the radioligand had it, compared with 4 in 100 on hormone therapy alone. None of those cases were serious, but dry mouth is persistent, it makes eating and sleeping harder, and it raises dental risk over time. That is a daily cost a man carries in exchange for a benefit he cannot feel.
Study Snapshot
PSMAddition is an ongoing randomised, controlled, phase 3 trial run at 169 sites in 20 countries, including hospitals, medical centres, and specialist cancer centres. Between June 2021 and July 2023, 1,529 men were screened and 1,144 were randomly assigned, half to each group. Median age was 68. Half had cancer that was already metastatic when first diagnosed, and 68 percent had high volume disease.
Men in the treatment arm received the radioligand by vein at 7.4 gigabecquerels every six weeks for up to six cycles, on top of hormone therapy. The comparison group received hormone therapy alone, and men whose cancer progressed on that arm were allowed to cross over to the radioligand. Progression was judged centrally by radiologists rather than by the treating doctors, which removes a common source of bias.
Safety, Limits, and Caveats
Serious side effects were more common with the added drug. Grade 3 or worse adverse events, meaning severe ones, occurred in 51 percent of men on the radioligand versus 43 percent on hormone therapy alone. Serious adverse events occurred in 32 percent versus 29 percent, and 3 percent of men in the radioligand arm had a serious event the investigators traced to the drug itself. Beyond dry mouth, the drug also caused more low blood counts and more stomach and bowel problems. Investigators reported no unexpected safety findings.
Two limits matter. This is an interim analysis of a trial still running, so the numbers can move. And the trial was open label, meaning everyone knew who got what, though the central review of scans blunts that concern for the main outcome.
Practical Takeaways
- If you or a family member has newly diagnosed metastatic prostate cancer, ask whether a PSMA PET scan has been done, since this treatment only applies to men whose tumors show PSMA on imaging.
- Ask your oncologist directly whether the survival data are mature before making a decision, because the benefit shown so far is on scans, not on how long men lived.
- Plan for dry mouth if you go ahead. Nearly half of treated men had it, so schedule a dental visit before starting and talk with your team about saliva substitutes and fluoride.
- Standard hormone therapy remains the backbone of treatment here, and nothing in this trial suggests replacing it.
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FAQs
What does PSMA-positive mean, and how do I know if I am?
PSMA stands for prostate-specific membrane antigen, a protein that sits on the surface of most prostate cancer cells. Doctors find it with a PET scan using a tracer called [68Ga]Ga-PSMA-11, which lights up wherever the protein is present. In this trial, every man needed at least one PSMA-positive lesion on that scan, read by a central team rather than the local site, before he could enroll. Men whose cancer does not show PSMA were not studied here, so the results say nothing about them.
Is this the same as regular radiation therapy for prostate cancer?
No. Standard radiation aims a beam from outside the body at a specific spot, which works well for cancer confined to one area. A radioligand is given through a vein and travels through the bloodstream, so it can reach deposits of cancer anywhere in the body at once. The radiation is carried directly to cells carrying the PSMA protein. That is why the treatment is used for cancer that has already spread rather than for a tumor still inside the prostate.
Why does the trial measure scans instead of how long men live?
Survival takes years to measure, especially in hormone-sensitive prostate cancer where men often live a long time on standard treatment. Radiographic progression-free survival, meaning time until a scan shows growth or the man dies, gives an earlier read. The trade-off is that it is a stand-in for what really matters. A drug can delay what a scan sees without adding months or years of life. PSMAddition is still running and will report survival later.
Bottom Line
Adding [177Lu]Lu-PSMA-617 to standard hormone therapy delayed prostate cancer progression in men with PSMA-positive metastatic disease, cutting the risk of progression or death by about 28 percent in a 1,144-man phase 3 trial. Severe side effects were more common in the treated group, and dry mouth affected nearly half of them, though none of those cases were serious. Survival data are not yet mature, so the strongest current claim is that this combination delays disease growth on imaging and may become a new option earlier in treatment than radioligand therapy has been used before.
