Can ERG protein expression be used to identify progression risk during active surveillance?

This article examined the association between ERG expression at prostate cancer diagnosis and the risk of disease progression during active surveillance.

One of the largest dilemmas in the treatment of prostate cancer is the management of a localized low-risk disease. Since radical prostatectomy (surgery to remove the prostate gland) is a complicated procedure with many possible complications, and early low risk cancer may take years to progress into a life-threatening condition, active surveillance is often recommended. During active surveillance no medical interventions are employed, but patients are routinely examined to determine disease progression. The current marker of choice in the surveillance of prostate cancer is PSA (prostate-specific antigen), a molecule produced in greater amounts during prostate cell growth. However, the use of PSA can contribute to the over-diagnosis of low-risk tumors, and may lead to unnecessarily aggressive treatments.

ERG is a protein important in the regulation of cell growth, division and death, the growth of new blood vessels and inflammation. The ERG protein is typically mutated in many types of cancer. Previous studies have indicated that ERG expression (as noted on analysis of a prostate biopsy) may be predictive of high risk cancer not suited for active surveillance.

This study examined whether ERG protein expression in prostate cancer tissue specimens is associated with the risk of disease progression during active surveillance.

265 patients undergoing active surveillance were followed for an average of 4 years. Biopsy results indicated that 142 patients had negative ERG expression, while 123 patients showed positive ERG expression at the time diagnosis.

Patients showing ERG-positive tumors were found to have a 2.5-fold higher risk of cancer progression during active surveillance compared to those with ERG-negative tumors. During the initial 2-year surveillance, 21.7% of ERG-negative patients experienced cancer progression, compared to 58.6% of ERG-positive patients. ERG expression was also noted to correlate with the rate of rise of PSA levels during active surveillance.

This study concluded that ERG status is an independent predictor of prostate cancer progression during active surveillance.