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.

The LUNAR trial's positive outcome was unexpected. Patients received SBRT for all PET-visible lesions, meaning the added Lutetium-PSMA was targeting disease that couldn't be seen. This implies the radioligand can effectively bind to and treat microscopic cancer cells, challenging the notion it only works on clearly imaged tumors.

The future of advanced prostate cancer treatment is shifting towards therapies that target cell surface markers. This new era will be defined by a growing arsenal of radioligands, T-cell engaging bispecific antibodies (BiTEs), and antibody-drug conjugates (ADCs) aimed at targets like PSMA, B7-H3, and HK2.

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.

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.

Unlike traditional CT scans, PSMA-PET scans visualize the biological heterogeneity of prostate cancer, showing which lesions are target-rich and which are not. While insightful, this "shines a flashlight" on the problem, creating new clinical challenges, such as how to manage a patient whose disease largely disappears except for two resistant lesions.

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.

Unlike chemotherapy, radioligand therapy's effectiveness wanes as tumors shrink. With less PSMA target for the drug to bind to, less radiation is delivered to the cancer. This physical reality supports "adaptive dosing"—stopping treatment in high-responders to spare healthy tissue and resume later if needed.