The results of an analytical validation study demonstrate that the Oncotype DX® prostate cancer test is a reliable assay, even with very limited RNA inputs, which enables successful performance using small amounts of cancer tissue typically available from prostate needle biopsies. The results of the study were published in BMC Genomics.
The treatment of early-stage prostate cancer is controversial because thus far there is no clear proof that aggressive treatment prolongs survival compared with deferred treatment. Furthermore, treatment can cause lasting side effects, such as impotence and incontinence. Some men opt for a more conservative approach, called active surveillance or watchful waiting—which defers treatment until symptoms appear and/or there is evidence of progression. This approach can help some men avoid unnecessary treatment and potentially long-lasting side effects; however, until now, it wasn’t possible to predict which cancers were aggressive and required treatment and which were slow-growing and could be watched until treatment was necessary.
The Oncotype DX prostate cancer test measures the level of expression of 17 genes across four biological pathways to predict prostate cancer aggressiveness. The test results are reported as a Genomic Prostate Score (GPS) that ranges from 0 to 100 and is combined with other clinical factors to further clarify a man’s risk prior to treatment intervention.
The objective of this study was to validate the accuracy of the Oncotype DX prostate cancer test by analyzing the test’s precision and accuracy in measuring gene expression over a wide range of conditions commonly encountered with diagnostic prostate biopsies.
Researchers measured, analyzed and compared gene expression in prostate cancer tissue samples taken from both radical prostatectomy and needle biopsy specimens. Gene assays were shown to accurately measure expression over a wide range of inputs (from as low as 0.005 ng to 320 ng).
The researchers noted that analytical accuracy was excellent. They concluded that the Oncotype DX Prostate Cancer Assay, which was specifically designed for use with prostate needle biopsies, has been analytically validated using very limited RNA inputs. They note that: “The assay requirements and analytical performance will provide physicians with test results from a robust and reliable assay which will enable improved treatment decisions for men diagnosed with early-stage prostate cancer.”
Knezevic D, Goddard AD, Natraj N, et al: Analytical validation of the Oncotype DX prostate cancer assay – a clinical RT-PCR assay optimized for prostate needle biopsies. BMC Genomics. 2013; 14:690. doi:10.1186/1471-2164-14-690