New Companion Diagnostic Expands Precision Medicine in Prostate Cancer

Tumors with loss of phosphatase and tensin homolog (PTEN) protein progress faster and may derive reduced benefit from standard therapies, underscoring the need for reliable pathology tools. A newly FDA-approved test now enables routine detection of PTEN protein loss to help identify patients eligible for a targeted combination regimen.

Roche’s VENTANA PTEN (SP218) RxDx Assay is the first immunohistochemistry (IHC) companion diagnostic to receive U.S. Food and Drug Administration (FDA) approval for determining PTEN protein loss in tumors of patients with prostate adenocarcinoma. The assay helps clinicians identify patients who may be eligible for treatment with TRUQAP (capivasertib). TRUQAP provides a new first-line treatment option for PTEN‑deficient metastatic androgen pathway modulation‑naïve or sensitive (mAPMN/S) prostate cancer, previously referred to as metastatic hormone‑sensitive prostate cancer.

The qualitative IHC assay evaluates PTEN protein expression in prostate adenocarcinoma, with staining performed using the OptiView DAB IHC Detection Kit on the BenchMark ULTRA instrument. The assay is indicated as an aid in identifying patients who may be eligible for TRUQAP in combination with abiraterone acetate, in accordance with approved therapeutic labeling. PTEN protein loss status is determined by the pathologist’s observation of PTEN expression within prostate adenocarcinoma, with a clinical cutoff defined as at least 90% of viable malignant cells showing no specific cytoplasmic staining.

FDA Approval was supported by the CAPItello‑281 clinical study, in which the assay served as the enrollment test to identify tumors exhibiting PTEN deficiency. In that trial, patients who received combination therapy with TRUQAP experienced a statistically significant and clinically meaningful reduction in disease progression.

Metastatic hormone-sensitive prostate cancer is an aggressive disease, with average survival after a new metastatic diagnosis estimated at about five to six years. About one quarter of these patients have PTEN-deficient tumors by immunohistochemistry. Foundation Medicine, an independent affiliate of the Roche Group, is one of the laboratories using the companion diagnostic kit to help guide patient selection.

“Prostate cancer is one of the leading cancer diagnoses for men in the United States,” said Matt Sause, CEO of Roche Diagnostics. “The FDA approval of our new companion diagnostic will provide clinicians with a vital tool to identify patients with PTEN loss and potentially provide new therapeutic options.”