"Staging factors for prostate cancer such as PSA and the Gleason score are extremely useful in predicting prostate cancer outcome," explained Pollack. "However, new biomarkers hold promise in strengthening our ability to predict response to treatment. By identifying the more virulent forms of prostate cancer, we may be able to tailor treatment or develop therapies to target the abnormalities identified."
In the Radiation Therapy Oncology Group-sponsored study (RTOG 92-02), Pollack and his colleagues show that the overexpression of a protein called MDM2 is a strong and independent predictor that the prostate cancer will metastasize beyond the prostate gland and indicates an increased chance of death from the disease.
The study involved 469 men treated with radiation and short- and long-term androgen deprivation therapy. The median follow-up was 70.5 months. An immunohistochemical analysis was conducted on prostate tissue to determine the amount of MDM2 in the prostate cancer cells.
While other biomarkers were associated with biochemical failure, distant metastasis or overall mortality, MDM2 was consistently associated with all three outcomes. MDM2 was associated with a doubling of distant metastasis (10 to 20 percent) and a nearly 10 percent reduction in five-year survival.