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Moderator Raoul Concepcion, MD, remarks that the use of biomarkers is related to the evolving and increasingly important field of personalized medicine. Clinicians discuss survival statistics with patients; however, these statistics are based on data from the population as a whole. At the level of the individual patient, outcomes vary among patients with prostate cancer with the same Gleason score. For the individual patient, the clinical outcome is dependent on the characteristics of his own unique tumor.
The challenge for clinicians is how to determine which patients are at higher risk for experiencing disease progression and therefore may need definitive therapy. Philippa Cheetham, MD, and Kenneth Kernen, MD, note that the results from the Oncotype DX test, which are reported as a Genomic Prostate Score (GPS), can provide information to clinicians to help with risk stratification. For example, for a patient with Gleason 6 prostate cancer, negative magnetic resonance imaging results, and stable prostate-specific antigen results, a high GPS might suggest the possibility of more aggressive disease. Cheetham adds that in her practice, she has observed that African American men tend to have higher GPS results than would be expected based on other clinical parameters.
Questions remain regarding the repeat use of Oncotype DX testing, remarks Michael Williams, MD. As a genomic marker, one would expect that the GPS would remain stable over time. However, in practice, it is not currently known whether the GPS from a biopsy taken at initial patient presentation would remain the same if another biopsy were taken 2 years later.
Neal Shore, MD, states that Oncotype DX testing has been validated and that the results have recently been published. Re-biopsy is not required for Oncotype DX testing, and only a small amount of tissue is required, according to Shore. Oncotype DX testing may only be conducted within 6 months of biopsy, notes Cheetham.