SUMMARY: Prostate cancer is the most common cancer in American men with the exclusion of skin cancer and 1 in 7 men will be diagnosed with prostate cancer during their lifetime. It is estimated that in the United States, about 161,360 new cases of Prostate cancer will be diagnosed in 2017 and 26,730 men will die of the disease. Traditionally, clinical risk assessment has been based on Tumor stage, Gleason score and PSA level, in patients who had Radical Prostatectomy for Prostate cancer. However, new validated biomarkers can improve risk stratification for men with Prostate cancer.
The Oncotype DX® Prostate Cancer Assay is a multi-gene RT-PCR expression assay that was developed for use with Fixed Paraffin-Embedded (FPE) Prostate needle biopsy specimens. This 17 gene assay measures expression of 12 cancer related genes representing four biological pathways with a known role in Prostate cancer development (androgen pathway, cellular organization, proliferation and stromal response), and 5 reference genes used to control for sources of pre-analytical and analytical variability. Combined together algorithmically, the Genomic Prostate Score (GPS, scale 0-100) is calculated, with a higher GPS score representing a more aggressive tumor phenotype. Genomic Prostate Score has been shown to predict unfavorable outcomes beyond conventional clinical and pathologic factors and has been validated as an independent predictor of adverse surgical pathology and BioChemical Recurence after Radical Prostatectomy, in men with low-risk and low-volume intermediate-risk Prostate cancer.
The authors conducted a large community based study, to confirm that Genomic Prostate Score (GPS) is a predictor of BioChemical Recurrence in all clinical risk groups (low, intermediate and high), in a large cohort of Prostate cancer patients, followed up at Kaiser Permanente medical groups in Northern California. A retrospective study was performed from the Kaiser Permanente clinical database of 6,184 Prostate cancer patients, between 1995- 2010, with NCCN very low, low, intermediate and high-risk disease, who were treated with Radical Prostatectomy. BioChemical Recurrence was defined as either 2 successive post-Radical Prostatectomy PSAs of 0.2 ng/mL or more, or initiation of salvage therapy after a rising PSA of 0.1 ng/mL or more. Genomic Prostate Score was derived from the archival biopsy tissue. The researchers were able to retrieve the biopsy tissue of 334 patients of whom 279 patients met all eligibility criteria and a valid GPS score was available in 259 (93%) patients.
It was noted that Genomic Prostate Score was strongly associated with BioChemical Recurrence after adjusting for PSA, clinical T stage and tumor Gleason Score (P=0.002). Genomic Prostate Score was a strong independent predictor of Prostate cancer-specific death and disease progression (metastases) at 10 years, across all NCCN clinical risk groups. Further, the association between GPS and BioChemical Recurrence was similar within the different racial groups.
It was concluded that for patients with Prostate cancer treated with Radical Prostatectomy, a higher Genomic Prostate Score was associated with BioChemical Recurrence, independent of other clinical factors. Genomic Prostate Score can hence improve risk stratification beyond clinical risk assessment, by predicting both near term adverse pathology and long term clinical outcomes Validation of a 17-Gene Genomic Prostate Score (GPS) as a predictor of biochemical recurrence (BCR) in men with prostate cancer treated with radical prostatectomy (RP) in a community setting. VanDenEeden SK, Zhang N, Quesenberry CP, et al. J Clin Oncol 35, 2017 (suppl 6S; abstract 41)