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.

Unlike traditional chemotherapy, radioligand therapy's toxicity may be inversely correlated with tumor volume. In low-burden disease, fewer cancer cells act as a 'sink' for the drug, potentially leading to higher radiation exposure and side effects in healthy, PSMA-expressing tissues like salivary glands.

Early in treatment, tumors are "target-rich" with high PSMA expression, creating an ideal window for radioligand therapy. Citing data from the VISION trial, new clinical trials are being designed to accelerate dosing and intensity upfront to maximize impact, then de-escalate as the target diminishes.

After years of successfully intensifying hormonal therapy, the focus in prostate cancer is shifting toward de-intensification. Researchers are exploring intermittent therapy for top responders and developing non-hormonal approaches like radioligands to spare patients the chronic, life-altering side effects of permanent castration.

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.

For patients with conventionally negative imaging but positive PSMA PET scans (oligometastatic disease), continuous intensified therapy may be overtreatment. A new paradigm involves metastasis-directed therapy followed by a short course of escalated treatment, then stopping to observe. This "time-limited" approach balances efficacy with reducing long-term treatment burden.

Medical oncologists are trained to treat continuously to eliminate micrometastatic disease. Radioligand therapy challenges this dogma, as its effectiveness is tied to target volume. As tumors shrink, the therapy becomes less potent against the cancer and relatively more toxic to healthy organs, requiring a mental shift to an adaptive, physics-based model.

A practical method to monitor radioligand therapy is a post-treatment SPECT scan. Since the therapeutic agent is radioactive, a simple planar scan about 24 hours after injection can visually confirm where the drug was delivered. This provides real-time feedback, beyond PSA levels, to potentially adapt treatment.

Instead of administering all six planned doses of PSMA Lutetium upfront in the hormone-sensitive setting, a novel "sandwich" strategy is being considered. This involves giving a few doses, re-imaging, and reserving subsequent doses for later, potentially optimizing efficacy and managing long-term toxicity.