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ASTRO 2015: Genomic Classifier Appears to Predict Metastasis in Patients With Prostate Cancer Following Prostatectomy

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Key Points

  • Data indicated that a patient’s genomic classifier score was the most significant factor in predicting the development of metastases 5 years after salvage radiation therapy, with genomic classifier low-risk patients having a 2.8% incidence of metastases at 5 years, genomic classifier average-risk patients having 5.8% incidence, and genomic classifier high-risk patients having 33.5% risk.
  • The 5-year incidence of metastases in patients with low, average, and high CAPRA-S scores, respectively, was 17%, 2.3%, and 15%.
  • For patients who were determined to be at low-risk by genomic classifier, there was no difference in the incidence of metastases regardless of the PSA value at which salvage radiation was initiated. For men with high risk, there was a significantly higher incidence of metastases in men receiving salvage radiation therapy with a PSA greater than 1.0 ng/mL compared to those with PSA between 0.2 and 1.0 ng/mL.

For men with prostate cancer who have had a prostatectomy and salvage radiation therapy, analyzing their tumor genome provides clues as to whether their cancer will metastasize, thereby enabling clinicians to better personalize treatment options, according to research presented by Den et al (Abstract 306) on October 21, 2015, at the American Society for Radiation Oncology (ASTRO) 57th Annual Meeting in San Antonio, Texas.

Prostate cancer treatment varies based on the severity and stage of the disease, with some patients requiring prostatectomy. For patients who develop elevated prostate-specific antigen (PSA) levels following a prostatectomy, additional treatment with salvage radiation therapy is generally the next step in treatment. Depending on other clinical indicators, the cancer metastasizing may be of concern, and in addition to radiation therapy, patients might also receive aggressive hormone therapy.

The recurrence of a high PSA level alone is not an ideal indicator of future metastatic disease; therefore, researchers in this study looked to determine whether a genomic classifier, known as a validated predictor of metastasis, could distinguish the patients for whom additional, aggressive therapy is beneficial from those for whom salvage radiation therapy on its own is likely sufficient.

Study Details

The study evaluated 166 prostate cancer patients—53 African American men (32%) and 113 white men (68%)—who received salvage radiation therapy between 1990 and 2010 at Thomas Jefferson University, Veteran Affairs Medical Center Durham, and Mayo Clinic. Genomic classifier scores were calculated for each patient based on genomic analysis of their own tumor tissue.

A postsurgical sample was used from each patient’s removed prostate (a tissue sample was removed from the prostatectomy specimen from the area containing the highest Gleason score) and compared 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. A patient’s 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

Data indicated that a patient’s genomic classifier score was the most significant factor in predicting the development of metastases 5 years after salvage radiation therapy, with genomic classifier low-risk patients having a 2.8% incidence of metastases at 5 years, genomic classifier average-risk patients having 5.8% incidence, and genomic classifier high-risk patients having 33.5%, compared to a 17%, 2.3%, and 15% incidence of metastases in patients with low, average, and high CAPRA-S scores, respectively.

For patients who were determined to be at low-risk by genomic classifier, there was no difference in the incidence of metastases regardless of the PSA value at which salvage radiation was initiated. For men with high risk, there was a significantly higher incidence of metastases in men receiving salvage radiation therapy with a PSA greater than 1.0 ng/mL compared to those with 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 salvage radiation therapy after radical prostatectomy,” said Robert Den, MD, Assistant Professor of Radiation Oncology at Sidney Kimmel Medical College at Thomas Jefferson University. “Indeed, the genomic classifier biomarker provides an insight regarding tumor aggressiveness in these individuals. Despite salvage local therapy for recurrent prostate cancer after radical prostatectomy, some patients continue to progress to metastases. 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.”

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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