Chicago, IL—A genomic test performed on a biopsy specimen that would discriminate between aggressive and indolent prostate cancer is a step closer to reality.
The goal of the test is to help guide treatment decisions at the time of prostate cancer diagnosis by looking at the gene expression profile of the tumor biopsy, said Eric A. Klein, MD, Chair of the Glickman Urological and Kidney Institute, the Cleveland Clinic (which is collaborating with Genomic Health to develop the test), at ASCO 2012.
Previous work by Dr Klein and colleagues showed that a number of genes that were strongly associated with clinical recurrence, prostate cancer death, and adverse pathology could be identified from radical prostatectomy specimens.
The current gene refinement study presented by Dr Klein demonstrates that these genes can predict adverse pathology at the time of diagnosis by quantitative assays performed on biopsy-tissue tumor specimens.
The expression of these genes provides risk information beyond that obtained from traditional pathological and clinical assessments (ie, biopsy Gleason grade, level of prostate-specific antigen [PSA], clinical stage), Dr Klein noted.
“What we’ve learned is that if you measure the expression of a specific set of genes on a biopsy, you can predict the likelihood that someone will have an indolent course versus someone who won’t,” he said. “We think that the gene expression profile can help reveal patients with apparent ‘low-risk’ disease who in fact have aggressive tumors that are not identified by the biopsy grade, clinical stage, or PSA.”
The limited tissue sampled with prostate needle biopsies had been a challenge in the development of a genomic test in localized prostate cancer.
Radical prostatectomy specimens from 441 patients with localized prostate cancer (low-to-intermediate risk by American Urological Association criteria) were first used to identify 374 prognostic genes. The expression of a subset of these genes and 5 reference genes was quantified by real-time polymerase chain reaction performed on prostate tumor tissue obtained through needle biopsy.
“Predictive genes from the gene identification study also predicted adverse pathology when assayed in biopsy tumor tissue,” Dr Klein said.
Of the 81 genes evaluated in the biopsy study, 58 (72%) predicted high-grade and/or nonorgan-confined disease.
The overexpression of androgen and cellular organization genes consistently predicted lower risk, whereas the overexpression of stromal response and proliferation genes predicted higher risk.
Dr Klein suggested that the test would include approximately 20 prognostic genes and will be validated in an independent, prospectively designed study of prostate biopsies.—WK