Researchers have identified a genetic signature that appears to reflect the risk of tumor recurrence or spread in men surgically treated for prostate cancer. If confirmed in future studies, this finding may help determine which patients require additional treatment after the cancerous gland has been removed. It also may help clinicians distinguish tumors that require aggressive treatment from those that can safely be monitored. The report was issued online in PNAS Early Edition.
The research team examined samples of malignant tissue from 200 prostate cancer patients who had radical prostatectomies at the Massachusetts General Hospital, analyzing the expression patterns of more than 1,500 genes associated with prostate cancer in earlier studies. With the results of that analysis, they developed a 32-gene index to reflect the likelihood that a patient's tumor would recur, signified by detectable levels of prostate-specific antigen (PSA) after the gland had been removed or the cancer had spread.
To validate the index’s usefulness, they employed it to analyze tissue samples from a different group of almost 300 patients who had their prostates removed, comparing the index with currently used prognostic factors to see how accurately each predicted the actual incidence of tumor recurrence or metastasis during the 10 years after surgery. The expression-based index proved to be the most accurate method. Among those it designated as high-risk, the actual incidence of tumor recurrence was 47%; the incidence of metastasis was 14%. Among those classified as intermediate risk, actual recurrence was 22%, and metastasis occurred in 2%. No recurrence or metastasis was seen in patients classified as low-risk by the gene-expression index. Read the study abstract.