Test predicts prostate cancer radiation therapy failure

A genomic test capable of predicting the probability of developing metastatic prostate cancer outperformed existing clinical risk factors for predicting biochemical failure and distant metastasis following radiation therapy, researchers reported at the Genitourinary Cancers Symposium in San Francisco.

In addition, researchers observed significant improvement in outcomes for patients with high-risk results on the Decipher Prostate Cancer Classifier test (GenomeDx Biosciences, San Diego) who received radiation therapy early rather than late after surgery.

“This is the first validation of the Decipher test in patients receiving radiation therapy following prostate surgery,” said co-author Adam Dicker, MD, PhD, of Thomas Jefferson University’s Kimmel Cancer Center, Philadelphia. “Decipher improved the ability to predict men at risk for biochemical failure and distant metastasis after postoperative radiotherapy over and above existing clinical risk factors such as Gleason score, tumor stage, and PSA. These data indicate that patients with a high Decipher result may benefit from earlier radiation and a multi-modal approach to treatment.”

In the study, 139 patients who had undergone radiation therapy after prostatectomy at Thomas Jefferson University between 1990 and 2009 were analyzed. RNA was extracted from the preserved tissue samples and run on the Decipher test. Patient histories were then analyzed to determine if Decipher was able to stratify patients who could have benefited from earlier radiation therapy.

In patients identified as high risk by Decipher, those who underwent early radiation therapy survived for a median of 8 years without biochemical failure, defined as an increase in PSA following radiation. This was compared to less than 4 years for patients who received late radiation therapy (p<.001). At 8 years following radiation therapy, high-risk Decipher patients who received early radiation therapy had a 3% cumulative incidence of metastasis versus 23% for patients with high-risk results who received late radiation therapy (p<.001).

“The findings of our study have ramifications for many of the current ongoing clinical trials evaluating post-prostatectomy radiation therapy,” said lead author Robert Den, MD, also of Kimmel Cancer Center. “They suggest that there is a subset of patients who would benefit from immediate treatment and those who can afford to postpone therapy.”

Dr. Den and two study co-authors receive research funding from GenomeDx, and one co-author is an employee of the company.

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