The effectiveness of radioligand therapy is counterintuitive: as tumors shrink and PSMA binding sites decrease, less radiation is delivered to the cancer. The VISION trial showed the first two doses delivered more radiation to the tumor than the subsequent four, questioning the value of a fixed, prolonged treatment schedule.

Clinicians may counsel patients towards therapies with lower efficacy if the dosing schedule is more convenient (e.g., quarterly). The rationale is that a lack of response is evident quickly, allowing a rapid pivot to another treatment without losing significant time or risking progression.

Lutetium faces criticism for its fixed 6-cycle regimen, which may be suboptimal as the PSMA target diminishes with ADT. However, this critique is rarely applied to other drugs like PARP inhibitors, which are given until progression. This highlights a double standard and the tension between using a fixed regimen for regulatory approval versus finding the optimal dose in practice.

Even if radioligand therapies like Lutetium-PSMA are approved for first-line metastatic prostate cancer, their real-world adoption will be significantly hampered by logistics. Most U.S. patients are treated in community practices that lack the infrastructure for these therapies, creating a major access and bandwidth problem that will temper uptake.

The CCTG PR21 trial revealed a paradox: patients treated with lutetium first had a PSA response rate double that of docetaxel chemotherapy. However, overall survival was better for the group that received docetaxel first. This highlights the complexity of sequencing and suggests initial response isn't always predictive of long-term outcomes.

Intensive treatments like ADT plus an ARPI can suppress a patient's PSA so effectively that it becomes an unreliable marker of disease status. Patients may show radiographic progression on scans even while their PSA remains low and they feel clinically well. This discordance necessitates periodic imaging to avoid missing actual disease progression.

If lutetium-PSMA is approved and used upfront in hormone-sensitive disease, clinicians may become more comfortable with radioligands generally. This could lead them to use the enzalutamide-radium combination more frequently later on, paradoxically increasing radium's use by flipping the current treatment sequence.

Clinicians may be biased towards lutetium-PSMA because it causes significant PSA drops, which radium-223 does not. This observable metric may not reflect superior overall efficacy, as radium's survival benefit is proven and it may even have unique synergistic potential with drugs like enzalutamide through different biological pathways.

While Lutetium shows promise in hormone-sensitive prostate cancer, experts raise concerns about potential late-effect toxicities for patients surviving many years. This contrasts with docetaxel, where toxicity is acute and resolves after treatment, highlighting an unknown long-term risk-benefit profile for new radioligand therapies.