Oncologists present test to predict survival in castration-resistant prostate cancer patients
Mar 1, 2009 - 9:12:50 AM
Dana-Farber Cancer Institute (DFCI) and Source MDx today
announced that Source MDx’s whole blood RNA transcript-based Precision Profiles™ diagnostic test predicted survival in men with castration-resistant prostate cancer (CRPC). In a study of 62 CRPC patients, the model separated patients into a high risk group (survival less than 2.2 years) and a low risk group (survival greater than 2.2 years) (log rank p=0.00083).
The six-gene CRPC Precision Profile™ was 96 percent accurate in predicting low risk CRPC patients alive at study end and 93 percent accurate in predicting high risk CRPC patients who died prior to study completion, suggesting that the model may be a powerful tool for stratifying CRPC patients in clinical trials. The Prostate Cancer Clinical Trials Consortium (PCCTC) will begin a prospective, multisite clinical trial to validate using Source MDx’s six-gene CRPC Precision Profile™ to stratify aggressive vs. non-aggressive CRPC patients.
In the study, circulating tumor cell (CTC) counts were not predictive of survival. In fact, the highest CTC counts (931 and 263) were found in patients from the low risk group. The Halabi nomogram, a commonly used clinical prognostic factor that uses seven clinical measures, also predicted low and high risk groups of men with CRPC, based on evaluations in 56 patients, but was less discriminatory (p=0.012) than the six-gene Precision Profile™.
William K. Oh, M.D., clinical director, Lank Center for Genitourinary Oncology, DFCI today presented the data from abstract 176 in a general poster session at the American Society for Clinical Oncology’s Genitourinary Cancers Symposium. The study was co-investigated with Robert W. Ross, M.D., attending physician, Lank Center for Genitourinary Oncology, DFCI. The PCCTC, a national clinical research group comprised of top U.S. research institutions, including DFCI, will conduct a prospective multi-site validation clinical trial of CRPC patients under the leadership of Dr. Oh. Consortium studies focus on the evaluation of novel agents for the management of prostate cancer at all stages of the disease. Source MDx has filed provisional patents on the six-gene model, which also states diagnostic claims for protein markers corresponding to patented RNA transcripts.
“Survival for castration-resistant prostate cancer ranges greatly from several months to several years, however, there are no available tools that allow clinicians to easily identify patients with the most aggressive form of the disease,” commented Dr. Oh. “The ability to identify patients with more aggressive forms of castration-resistant prostate cancer using a simple blood assay may prove to be a powerful tool for stratifying patients in clinical trials, leading to more robust studies with more relevant survival endpoints. I look forward to further evaluating this biologically-based test in forthcoming larger, multi-site clinical trials with the Prostate Cancer Clinical Trials Consortium.”
These data also show that individual differences in gene transcripts associated with cell-mediated and humoral immunity are associated with survival in CRPC patients. These specific immune system changeswere indicative of a decrease in both cell-mediated and humoral immunity in CRPC patients with higher mortality.
“The six genes predictive of more lethal castration-resistant prostate cancer in this trial suggest a fundamental difference in a patient’s immune system’s ability to deal with malignant tumors when confronted with more aggressive forms of prostate cancer,” stated Karl Wassmann, Chief Executive Officer of Source MDx. “The Source MDx six-gene CRPC Precision Profile™ is now available for patient stratification in prostate cancer clinical trials.”
About the Study:
From August 2006 through June 2008, Source MDx and Dana-Farber Cancer Institute conducted a study to discover whole blood-based RNA-transcript biomarkers predictive of primary end-points of CRPC progression (i.e., survival). The study enrolled a total of 62 CRPC patients, with or without bone metastases, who had previously undergone a variety of treatments, including hormone therapy, chemotherapy and radiation. Each patient consented to the collection of whole blood in PAXgene™ blood RNA tubes for gene expression and CellSave™ tubes for the enumeration of circulating tumor cells (CTCs). Using Source MDx Precision Profiles™, a total of 168 inflammation and prostate cancer-related genes were evaluated using optimized Q-PCR technology to assess biomarkers predictive of survival. Hazard ratio survival analysis models were performed on a weekly basis, both from the time of CRPC diagnosis through June 20, 2008 and from the time of blood draw through June 20, 2008. The results were similar regardless of the survival time definition (the time of castration-resistant diagnosis vs. blood draw) or the survival model used for statistical analysis. Treatment type was not predictive of survival.
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