An abstract presenting validation data for the Decipher prostate cancer classifier from GenomeDx Biosciences, San Diego, was selected for presentation at the 2015 Best of ASTRO conference and recognized at the American Society for Therapeutic Radiology and Oncology (ASTRO) annual meeting in San Antonio, Texas.
“Validation of a Genomic Classifier for Prediction of Metastasis Following Postoperative Salvage Radiation Therapy” presented findings derived from use of the Decipher genomic test, which provides an assessment of tumor aggressiveness. Used by urologists and radiation oncologists during treatment planning, the Decipher test offers insight that is distinct from clinical measures of risk, including prostate-specific antigen (PSA) levels and Gleason score.
Prostate cancer treatment varies according to the severity and stage of the disease, with some patients requiring prostatectomy, surgical removal of the prostate. For patients who develop elevated PSA levels following a prostatectomy, indicating that cancer cells remain in the body, additional treatment with salvage radiation therapy (SRT) is generally the next step in treatment. Depending on other clinical indicators, metastasis of the cancer may be of concern; in that case, in addition to radiation therapy patients may receive aggressive hormone therapy, which can aid in treating the cancer by suppressing male hormones.
Because recurrence of a high PSA level alone is not an ideal indicator of future metastatic disease, researchers in the Decipher study sought to determine whether a genomic classifier (GC) previously validated as a predictor of metastasis could distinguish the patients for whom additional, aggressive therapy would be beneficial from those for whom SRT alone would likely be sufficient.
The study evaluated 166 prostate cancer patients: 53 African-American men (32%) and 113 Caucasian-American men (68%) who received SRT between 1990 and 2010 at Thomas Jefferson University, the Mayo Clinic, or the Veteran Affairs Medical Center in Durham, NC. GC scores were calculated for each patient based on analysis of their tumor tissue.1 From each patient’s prostatectomy specimen, the researchers removed a tissue sample from the area containing the highest Gleason score, and compared it to the patient’s cancer of the prostate risk assessment postsurgical (CAPRA-S) scores using survival c-index, competing-risks, and Cox regression analysis for the prediction of metastasis. CAPRA-S scores are based on clinical risk factors such as presurgical PSA score, Gleason score, area around the prostate affected by cancer, and lymph node involvement.
Study findings indicated that a patient’s GC score was the most significant factor in predicting the development of metastases within 5 years after SRT. GC low-risk patients had a 2.8% incidence of metastases at 5 years, GC average-risk patients had a 5.8% incidence, and GC high-risk patients had a 33.5% incidence. By comparison, patients with low, average, and high CAPRA-S scores had 17%, 2.3%, and 15% incidence of metastases, respectively.
Among patients determined by GC to be at low risk, the PSA value at which salvage radiation was initiated made no difference for the incidence of metastases. Among men determined to be at high risk, however, those with a PSA level greater than 1 ng/ml on initiation of SRT had a significantly higher incidence of metastases than those with a PSA between 0.2 and 1.0 ng/ml.
“Our findings are particularly intriguing and provide a unique, more individualized approach to managing men receiving SRT after radical prostatectomy (RP),” says lead study author Robert Den, MD, assistant professor of radiation oncology at Sidney Kimmel Medical College at Thomas Jefferson University. “Indeed, the GC biomarker provides an insight regarding tumor aggressiveness in these individuals.
“Despite salvage local therapy for recurrent prostate cancer after RP, some patients continue to progress to metastases,” Den explains. “Identifying these men may allow them to undergo systemic therapy, including testing novel therapies to reduce the risk of metastases. And, the men at low risk of progression can be spared treatment intensification, such as high-dose hormone therapy, which may lead to permanent side effects.”
Decipher is covered by Medicare and multiple private insurance plans in the United States. For more information, visit GenomeDx.
- Den RB, Choeurng V, Howard L, et al. Validation of a genomic classifier for prediction of metastasis following postoperative salvage radiation therapy [abstract no. 306]. San Antonio, Texas: Annual meeting of the American Society for Therapeutic Radiology and Oncology, October 21, 2015. Int J Radiat Oncol Biol Phys. 2015;93(3):suppl S134; doi: 10.1016/j.ijrobp.2015.07.320.