The presence of the ERG protein in biopsied prostate tissue appears to substantially raise the likelihood that prostate cancer (PCa) will develop, according to researchers.

The findings emerged from a post-hoc analysis of data obtained from a phase 3 clinical trial involving 1,590 men with biopsy-diagnosed high-grade prostatic intraepithelial neoplasia (HGPIN). The men had been randomized to treatment with toremifene or placebo for three years or until a diagnosis of PCa was made on prostate biopsy. As part of the study, a pathologist evaluated biopsies of men with HGPIN at baseline and at 12, 24, and 36 months of follow-up. The tissue was tested for the presence of ERG.

ERG expression was detected in 51 of 461 patients (11.1%) with isolated HGPIN. More than one-third of that group (36.9%) group received a diagnosis of PCa at some point during the three-year study period, with 14.7% receiving the diagnosis during the first year. PCa developed in 27 of 51 ERG-positive men (53%) compared with 143 of 410 ERG-negative patients (35%). ERG expression was not associated with age, baseline prostate-specific antigen (PSA) level, Gleason score, or tumor volume.

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“This study underscores the necessity of more stringent follow-up for men with HGPIN that is also positive for ERG overexpression,” Mark A. Rubin, MD, of Weill Cornell Medical College and New York–Presbyterian Hospital in New York, and colleagues concluded in the Journal of Clinical Oncology. “Clinicians should consider molecular characterization of HGPIN as a means to improve risk stratification.”