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.

While PSMA PET scans are more sensitive, they create a clinical dilemma because pivotal trials defining treatment efficacy were based on conventional imaging (CT/bone scans). This forces oncologists to either re-image patients with older technology to match trial criteria or make treatment decisions based on PET data that lacks a clear evidence-based framework for response assessment.

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.

The patient population in pivotal trials like EMBARK, defined as non-metastatic by conventional imaging, is being re-evaluated. A UCLA study showed that over 80% of a similar patient group would have been positive on a PSMA PET scan, suggesting the "M0" classification is largely an artifact of older imaging technology and that these patients likely have micrometastatic disease.

The advent of highly sensitive PSMA PET imaging is changing the management of biochemically recurrent prostate cancer. Rather than relying on fixed PSA thresholds from older trials like EMBARK to restart therapy, clinicians now use PET imaging at lower PSA levels to guide decisions, aiming to extend treatment-free intervals.

Blocking the androgen receptor with enzalutamide can increase PSMA expression. In patients on enzalutamide alone, this predicts a poor outcome. However, for patients receiving combination therapy, this increased expression creates a better target for lutetium-PSMA, effectively mitigating the negative prognosis and improving survival.

PSMA-PET imaging at baseline can identify who benefits from adding lutetium-PSMA. In the ENZA-P trial, patients with high-volume disease saw a significant survival benefit from the combination. Conversely, those with low-volume disease derived no benefit, suggesting imaging can be used for patient selection.

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.

NCCN now recommends PSMA PET as a potential replacement for traditional CT, MRI, and bone scans for initial staging of higher-risk prostate cancer and detecting recurrence. This shift is based on PSMA PET's superior sensitivity and specificity for finding micrometastatic disease, positioning it as a more effective frontline tool.