Two Genetic Tests Can Prevent Overtreatment of Early Prostate Cancer

July 2013, Vol 4, No 6

Chicago, IL—The management of patients with prostate cancer will be advanced by 2 new genetic tests—Oncotype DX prostate cancer test and Prolaris. Both tests generate a score that can be used to analyze biopsy specimens of men with low-risk prostate cancer (ie, Gleason score ≤6) to determine if they are truly “low risk” and appropriate for watchful waiting, or if they harbor higher-risk genes and need immediate treatment.

These tests, although expensive, have the potential to prevent overtreatment and the associated costs, and to improve decision-making and risk assessment.

Studies presented at the 2013 Ameri­can Society of Clinical Oncology meeting focused on the 2 tests, which experts believe will compete with each other for market share.

Oncotype DX for Prostate Cancer Expecting FDA Approval
Launched by Genomic Health on May 18, 2013, the Oncotype DX prostate cancer test is similar to the Oncotype DX breast cancer and colon cancer tests widely used in the United States.

The Oncotype DX prostate cancer test measures the expression of 17 genes in a prostate tissue specimen that can predict the aggressive level of prostate cancer by generating a genomic prostate score ranging from 0 to 100.

H. Jeffrey Lawrence, MD, Senior Director of Medical Affairs, Genomic Health, Redwood City, CA, presented data showing that the expression patterns that predict prostate cancer aggressiveness are similar in tumor tissue and in normal prostate tissue. The genomic prostate score derived from tumor-based gene-expression patterns in the tumor was also associated with clinical recurrence when assessed in adjacent normal prostate tissue, but the strength of the association was less robust than in the tumor. The genes associated with the strong­est predictive value of the genomic prostate score in normal tissue were those representing stromal response and androgen signaling.

A validation study of the Oncotype DX prostate cancer test was presented at the 2013 meeting of the American Urological Association by Peter Carroll, MD, Professor and Chair, Department of Urology, University of California, San Francisco.

The test significantly predicted disease aggressiveness (P = .002) beyond clinical factors that included prostate-specific antigen level and Gleason score.

The test is estimated to cost approximately $3800. Genomic Health is in the process of building a dossier of evidence for insurers. Based on Genomic Health’s strong track record with the breast and colon cancer Oncotype DX assays, the company expects the US Food and Drug Administration (FDA) to grant approval to the prostate test.

Prolaris Approved by FDA
Prolaris, manufactured by Myriad Genetics, is approved by the FDA for use in low-risk men with a Gleason score of 6, and for patients postprostatectomy who are at high risk for prostate cancer recurrence. Prolaris, which has been available for several months, costs approximately $3400.

The assay generates a cell cycle progression (CCP) score based on the average RNA expression of 31 CCP genes that are normalized by the average expression of 15 housekeeping genes as quantitated by reverse transcriptase polymerase chain reaction.

Jack M. Cuzick, PhD, Director, Wolfson Institute of Preventive Medicine, University of London, United Kingdom, presented a retrospective review of 5 studies of the Prolaris test showing that the test-generated CCP score was able to predict prostate cancer outcomes in multiple patient cohorts and in diverse clinical settings.

In a statement issued before the meeting, Dr Cuzick said, “Clinical data show that PROLARIS predicts prostate cancer outcome in multiple patient cohorts and in diverse clinical settings. PROLARIS provides independent information beyond clinicopathologic variables and accurately differentiates aggressive prostate cancer from indolent cancer based on real oncologic outcomes.”

 A similar distribution of CCP scores was found in all 5 studies, showing its utility in different settings. The CCP score was a significant predictor of disease outcome.

However, the 5 studies were not randomized; therefore the results should be interpreted with caution, Dr Cuzick said.

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