The prevalence of PTEN loss is not static; it increases significantly as prostate cancer advances. While less common in localized disease, it can be found in up to 25% of patients with metastatic disease. This escalating frequency with disease progression underscores its role as a key driver of cancer advancement and a critical therapeutic target in later stages.

Oligometastatic prostate cancer accompanied by PTEN loss behaves aggressively and rapidly converts into polymetastatic disease or castration resistance. Dr. Neeraj Agarwal warns against being misled by low volume into using metastasis-directed radiation. Radiation trials lack large phase 3 confirmation and perform poorly in tumor suppressor gene mutations. Oncologists should proceed straight to aggressive systemic targeted therapy rather than wasting time arranging oligometastatic radiation.

The CAPItello-281 trial shows the benefit of the AKT inhibitor capivasertib is on a spectrum. Patients with 100% PTEN protein loss by IHC derive a much greater benefit than those with partial loss, suggesting a quantitative biomarker may optimize patient selection.

The approval of the AKT inhibitor Capivasertib has transformed PTEN testing from a prognostic tool for aggressive disease into a mandatory predictive test. Every patient with newly diagnosed metastatic prostate cancer should be assessed to determine eligibility for this targeted therapy, marking a significant shift in the standard of care.

Because PTEN loss is an early, truncal mutation in prostate cancer, clinicians should perform NGS testing on the first day a patient is seen. This proactive approach ensures that crucial biomarker information is not lost and is available to guide future treatment decisions, such as the use of an AKT inhibitor, should the disease progress.

While Next-Generation Sequencing (NGS) is common, the FDA label for Capivasertib specifically requires Immunohistochemistry (IHC) to establish PTEN deficiency for treatment eligibility. This is because the critical factor is the functional loss of the PTEN protein, which IHC directly measures, making it non-negotiable for insurance approval.

Unlike androgen receptor mutations which arise under treatment pressure, PTEN loss is an earlier event. Therefore, archival tissue from a primary biopsy is generally sufficient for determining PTEN status, even years later at metastatic relapse, avoiding a new invasive procedure.

In the CAPITELO-281 trial, one-third of prostate cancer patients with PTEN deficiency demonstrated radiographic or clinical progression without meeting standard PSA progression criteria. Dr. Neeraj Agarwal stresses that clinicians should not rely on PSA monitoring alone in this cohort. Instead, oncologists must convince reluctant patients to undergo routine CT, bone, or PSMA PET scans to avoid catastrophic consequences like paraplegia from unmonitored spinal cord compression.

Unlike androgen receptor mutations that arise under treatment pressure, PTEN loss is an earlier event. Therefore, tissue from an original biopsy or prostatectomy remains informative for testing PTEN status when a patient relapses with metastatic disease, simplifying the diagnostic process and avoiding invasive re-biopsies.