PSMAfore: Advances in Targeted Prostate Cancer Therapy

The PSMAfore trial established that a targeted radioactive therapy called lutetium-177 PSMA-617 can delay disease progression in men with metastatic prostate cancer who have not yet received chemotherapy, moving this treatment earlier in the course of the disease than previously approved. Before PSMAfore, this therapy was only available to patients who had already gone through both hormonal drugs and chemotherapy. The trial’s results, and the guideline changes that followed, represent a meaningful shift in how advanced prostate cancer is treated and when targeted radiotherapy enters the picture.

What PSMA-Targeted Therapy Actually Does

Prostate-specific membrane antigen is an enzyme found on the surface of prostate cancer cells, and it tends to be far more abundant on cancer cells than on normal tissue. The therapy exploits this by attaching a radioactive element, lutetium-177, to a small molecule that locks onto PSMA like a key in a lock. Once the compound binds to a cancer cell, the lutetium-177 emits radiation that damages the cell’s DNA over a very short range, destroying the tumor while largely sparing surrounding healthy tissue.¹ The formal drug name, vipivotide tetraxetan, refers to the PSMA-binding molecule itself; the lutetium-177 is the payload it carries.

The concept behind this approach, sometimes called theranostics, is that the same molecular target used to find the cancer on imaging scans can also be used to deliver treatment. A PSMA PET/CT scan lights up wherever PSMA-expressing tumors are hiding in the body. If the scan confirms the tumors are PSMA-positive, the patient is a candidate for the therapy. If tumors do not express enough PSMA, the drug has nothing to bind to and the treatment would be ineffective.

The PSMAfore Trial Design

PSMAfore enrolled men with metastatic castration-resistant prostate cancer who had progressed on one prior hormonal therapy (an androgen receptor pathway inhibitor such as abiraterone or enzalutamide) but had never received chemotherapy. These patients were randomly assigned in equal numbers to receive either lutetium-177 PSMA-617 or a switch to the other hormonal agent they had not yet tried.² The trial ran at 74 sites across Europe and North America.

Patients in the radioligand therapy arm received an intravenous dose of about 7.4 gigabecquerels every six weeks for up to six cycles. Those randomized to the hormonal switch arm took their new drug by mouth on a continuous daily schedule. An important design feature was that patients in the hormonal-switch arm who showed confirmed disease progression on imaging were allowed to cross over and receive lutetium-177 PSMA-617.² That crossover provision made the trial more ethical for participants but also made it harder to see a clean survival difference between the two arms, since many control-arm patients eventually received the experimental treatment as well.

The primary endpoint was radiographic progression-free survival, meaning how long patients went before their scans showed the cancer growing again. The trial met this endpoint, showing a benefit for the lutetium-177 arm.³ Final overall survival and safety data were subsequently reported, though the crossover complicated interpretation of that secondary endpoint.

How PSMAfore Changed the Treatment Landscape

Before PSMAfore, lutetium-177 PSMA-617 had been approved on the strength of the VISION trial, which enrolled patients much further along in their disease: they had already failed both hormonal therapy and at least one round of taxane chemotherapy.⁴ PSMAfore’s contribution was proving the drug could help patients who had not yet gone through chemotherapy, essentially pulling the therapy forward by one or more treatment lines.

This matters in practical terms. Chemotherapy with docetaxel or cabazitaxel is effective but takes a physical toll, and some patients are not fit enough for it or prefer to avoid it if alternatives exist. With PSMAfore’s data in hand, physicians gained the option of offering targeted radioligand therapy earlier, potentially while patients are still in better overall health and more likely to tolerate treatment well.

Major clinical guidelines responded. The NCCN guidelines (version 1.2025) incorporated lutetium-177 PSMA-617 as an option for taxane-naive patients progressing after hormonal therapy, while the EAU 2025 guidelines acknowledged the expansion more cautiously.⁵ The recommended regimen remains six cycles given every six weeks, with ongoing androgen deprivation therapy and multidisciplinary team oversight.

Quality of Life and Pain

Cancer trials often focus on survival numbers, but for patients living with metastatic disease, how they feel day to day can matter just as much. PSMAfore collected detailed quality-of-life data, and the results favored the radioligand therapy arm across the board. Patients receiving lutetium-177 PSMA-617 maintained their quality of life for roughly seven and a half months before meaningful worsening, compared to about four and a quarter months for those switched to another hormonal drug.⁶

Pain control followed a similar pattern. Time to worsening of pain intensity was about five months in the lutetium-177 arm versus roughly three and a half months in the hormonal-switch arm. Prostate cancer that has spread to bone can cause debilitating skeletal events like fractures or spinal cord compression, and the radioligand therapy substantially delayed those as well. The median time to a first symptomatic skeletal event was not even reached in the lutetium-177 group during the study period, while it was about 18 months in the control arm.⁶ For men whose cancer has spread to their bones, this kind of delay in painful complications is not an abstraction on a chart; it is months of better daily function.

Who Gets Selected and How Imaging Guides Decisions

Not every patient with metastatic prostate cancer benefits equally from this therapy, and the imaging that goes into patient selection is increasingly sophisticated. PSMA PET/CT is the backbone: it confirms that a patient’s tumors express enough PSMA to be targetable. Beyond that binary yes-or-no, researchers have found that features visible on the baseline scan can predict how well a patient is likely to respond. Tumor volume, average uptake intensity, and how much variation exists in PSMA expression from one tumor deposit to the next all carry prognostic information.⁷

An artificial intelligence tool called SelectPSMA has been tested on baseline scans to predict treatment outcome before the first dose is even given. In one real-world analysis of 71 patients treated after regulatory approval, the algorithm flagged about a quarter of patients as likely nonresponders. Those patients went on to have dramatically lower PSA response rates and shorter survival compared to patients the algorithm classified as likely responders, with a median overall survival of roughly six months versus about 14 and a half months.⁸ If validated in larger studies, tools like this could help avoid treating patients who are unlikely to benefit, sparing them side effects and allowing earlier access to alternative therapies.

When Tumors Stop Showing Up on PSMA Scans

One of the trickier problems in PSMA-targeted therapy is what happens when some cancer deposits lose their PSMA expression during treatment. These lesions become invisible on PSMA PET/CT but can still be metabolically active and detectable on a different kind of scan, FDG PET/CT, which highlights glucose consumption instead. This mismatch is called FDG-positive, PSMA-negative discordance, and it represents disease that the therapy cannot reach.

A study of patients receiving PSMA radioligand therapy found that having even one such discordant lesion at baseline was associated with dramatically shorter survival: a median of six months compared to 16 months in patients whose tumors were uniformly PSMA-positive.⁹ Interestingly, some discordant lesions appear to develop during treatment rather than existing from the start. In a small study, about 13% of patients showed new FDG-positive, PSMA-negative deposits after two cycles of therapy, rising to about 22% after four cycles, though in that particular study the appearance of these lesions did not significantly affect survival.¹⁰

The clinical takeaway is that FDG PET/CT may add important information before and during radioligand therapy, especially for identifying patients harboring aggressive tumor clones that lack PSMA expression. Several groups are now investigating dual-tracer imaging protocols to better select patients and catch treatment failures early. Whole-body diffusion-weighted MRI is also being explored as an additional monitoring tool.⁷

Why Some Patients Do Not Respond

Resistance to PSMA radioligand therapy remains poorly understood, but the leading explanations fall into a few buckets. The most straightforward is that some cancer cells simply do not express PSMA, or lose it over time, making them invisible to the drug. Molecular changes within tumor cells can also confer radioresistance, meaning the cells absorb the radiation but repair the DNA damage before it kills them. And in cases where disease has spread to many tiny deposits, the drug may not deliver a lethal dose to each one because the radiation’s range is so short that isolated microscopic clusters receive subtherapeutic exposure.¹¹

Understanding resistance is where much of the current research energy is directed. The challenge is multifold: prostate cancer is genetically heterogeneous, meaning different deposits within the same patient can behave differently. A therapy that wipes out the PSMA-expressing majority may leave behind a PSMA-negative minority that eventually drives disease progression. Strategies to address this include combining radioligand therapy with other agents and developing more potent radioactive payloads.

Alpha Emitters and Next-Generation Payloads

Lutetium-177 is a beta emitter, meaning it releases electrons that travel a few millimeters through tissue. That range is useful for irradiating a cluster of tumor cells, but it may not deliver enough concentrated damage to resistant clones or very small metastases. Actinium-225, an alpha emitter, releases much heavier particles over a shorter range, depositing far more energy per cell. Early evidence suggests that actinium-225-PSMA therapy can produce responses in patients whose tumors have stopped responding to lutetium-177.¹²

Alpha therapy comes with caveats, though. The intense local radiation can cause more damage to salivary glands and kidneys than lutetium-177, and the short supply of actinium-225 has limited clinical use to small pilot studies and compassionate access cases. Several groups worldwide are working to increase actinium-225 production, and randomized trials are being planned. For now, actinium-225 remains an experimental rescue option rather than a standard treatment, but it signals the direction the field is heading.

Combining Radioligand Therapy with Immunotherapy

Prostate cancer has historically been resistant to immunotherapy. The tumors tend to have a “cold” immune environment, meaning few immune cells infiltrate the cancer. Radiation, however, has long been known to provoke immune responses by exposing tumor-cell contents to the immune system as cells die. This observation has generated interest in pairing radioligand therapy with immune checkpoint inhibitors, drugs that release the brakes on the immune system.

Early prospective studies have begun testing this combination, and emerging evidence supports the idea that lutetium-177 PSMA-617 may have immunostimulatory effects that complement checkpoint inhibitors.¹³ Whether this translates into meaningful survival gains remains to be seen in larger randomized trials, but it represents one of the more promising combination strategies under investigation. Other combinations being explored include pairing the radioligand therapy with DNA damage repair inhibitors (PARP inhibitors), which could make cancer cells less able to fix the radiation-induced damage.

Radiation Safety for Patients Treated as Outpatients

Because the therapy involves injecting a radioactive substance, patients and their families naturally wonder about radiation exposure to those around them. Lutetium-177’s radiation profile makes outpatient treatment feasible in most cases. Studies measuring radiation doses to household contacts found that caregivers who stayed near treated patients over several days received average total exposures of about 200 microsieverts, well within accepted safety limits for the general public.¹⁴

The external dose rate from a treated patient drops below standard safety thresholds within about five to six hours after the injection. Practical precautions typically include sleeping in a separate bed for the first night or two, flushing the toilet twice after use, and washing hands thoroughly. These measures are modest compared to what is required for some other radionuclide therapies, and they allow most patients to return home the same day they receive treatment.

Supply Chain Considerations

As clinical use of lutetium-177 has expanded from a niche therapy to a mainstream treatment option, questions about long-term supply have grown louder. Producing the high-purity form of lutetium-177 required for therapy depends on nuclear reactor irradiation of enriched ytterbium targets, a process concentrated in a small number of facilities worldwide. A commentary in the nuclear medicine literature noted that while current supply is adequate, structural adaptations in reactor capacity, processing facilities, and distribution logistics are needed to prevent future shortages as global demand scales up.¹⁵

The supply concern is not theoretical. Lutetium-177 has a half-life of about 6.6 days, which means it cannot be stockpiled. Each dose must be produced, shipped, and administered within a tight window. Any disruption at a production reactor or processing facility can ripple through treatment schedules at hospitals hundreds of miles away. Efforts to diversify the production base and develop alternative production methods are underway, but the logistical fragility of the supply chain is something the oncology community is actively watching.

How PSMA Went from Lab Curiosity to Cancer Target

The story of how PSMA became a therapeutic target stretches back to 1987, when a team led by Horoszewicz developed an antibody that recognized a protein on the surface of prostate cancer cells. By 1993, the gene encoding PSMA had been cloned, and researchers recognized its potential as a site for imaging and targeting metastatic disease.¹⁶ But turning that observation into a practical therapy took decades of chemistry work.

A pivotal breakthrough came from neuroscience, of all places. Researchers at Georgetown University in 2001 developed small molecules that inhibited an enzyme in the brain called GCP-II, which happens to be the same protein as PSMA. A team at Johns Hopkins realized these urea-based compounds could be repurposed as PSMA-targeting agents and modified for radiolabeling. The resulting scaffolds became the basis for both diagnostic PET tracers and the therapeutic compound used in PSMAfore.¹⁶ ¹⁷ Most PSMA-targeted agents used today, including the one in lutetium-177 PSMA-617, trace their molecular ancestry back to those early urea-based compounds. The path from a brain enzyme inhibitor to a prostate cancer drug is a reminder that some of the most consequential developments in medicine come from connecting work across fields that would not normally talk to each other.