Analytic and Clinical Validation of a Prostate Cancer–Enhanced Messenger RNA Detection Assay in Whole Blood as a Prognostic Biomarker for Survival

Abstract

Background Biomarkers based on detecting prostate cancer-specific transcripts are associated with inferior outcomes, but their validation in a clinical context is lacking. Objective To determine whether detecting prostate cancer enhanced transcripts in whole blood using an analytically valid assay has prognostic significance relative to circulating tumor cell (CTC) enumeration. Design, Setting, and Participants The predictive value for overall survival of the detection in whole blood by reverse transcription real-time polymerase chain reaction (RT-PCR) of KLK3, KLK2, HOXB13, GRHL2, and FOXA1 was studied in 97 men with metastatic castration-resistant prostate cancer (mCRPC). Intervention 2.5ml of blood was collected in PAXgene tubes for total RNA extraction and 7.5 ml for CTC enumeration from patients with progressive mCRPC. Outcome Measurements and Statistical Analysis Prostate cancer enriched genes were detected using a sensitive RT-PCR assay in whole blood from patients with mCRPC. Analytical validity of the assay was established in a clinical laboratory environment. The frequency of detecting transcripts was compared to CTC enumeration using CellSearch® in an independent data set and survival associations were explored by concordance probability estimate (CPE). Results and Limitations Two or more genes were detected by PCR in 53% (51 of 97, 95% CI 43–63%) of patients, and unfavorable CTC counts (≥5cells) were seen in 46% (45 of 97, 95% CI 36–56%). Importantly, transcripts were detectable in 11 of 52 patients with favorable CTC counts (21%, 95% CI 8–35%). Transcript detection predicted overall survival in a proportional hazards model. Significantly, the predictive accuracy of RT-PCR detection in combination with CTC enumeration had a CPE of 0.752 (SE=0.038), although limited by the number of patients. Conclusions This validated RT-PCR assay detecting prostate-specific RNA in whole blood is prognostic for survival, and may assess patient risk complimentary with CellSearch CTC enumeration. Its clinical utility is being prospectively explored.

Blood and tissue neuroendocrine tumor gene cluster analysis correlate, define hallmarks and predict disease status

“…Similar methodologies are evolving for solid tumors, e.g. MACC1 in gastric cancers (Burock et al 2015) or a panel of prostate cancer-associated genes in prostate cancer (Danila et al 2014). Hematological cancer measurements clearly reflect a pathobiological process as expression of fusion transcript levels correlate well (R 2 Zw0.5) between bone marrow and blood (Ostergaard et al 2004).…”

Genomic Predictors of Outcome in Prostate Cancer

“…Recently Danila et al investigated the detection of CTCs and the expression of five genes frequently detected in PCa cells (but not in peripheral mononuclear cells) utilizing reverse transcriptase-polymerase chain reaction (RT-PCR) to detect transcripts from peripheral blood [92]. Both unfavorable CTC count (five or more cells) and detection of two or more gene transcripts had similar significant prognostic value for risk of PCa death, and when combined, additional prognostic value was demonstrated.…”

A comprehensive review of genomic landscape, biomarkers and treatment sequencing in castration-resistant prostate cancer

“…As such, other liquid biopsy techniques including circulating cell-free tumor DNA may help to identify genomic alterations and track patient's genomic landscape over time to assess individual prognosis and adapt further treatment strategies. [37,38] The RT-PCR [45]. After combining the results of gene profile with CTCs counts, risk group were defined to pinpoint patients with poor prognosis.…”

“…After combining the results of gene profile with CTCs counts, risk group were defined to pinpoint patients with poor prognosis. This RT-PCR assay detecting prostatespecific RNA in whole blood associated with CTCs count is currently being prospectively tested as a prognostic factor and response indicator [45]. Loss of PTEN expression has also been reported to be associated with worse survival [46] and analyses of extracellular microRNAs embedded in circulating exomes revealed that plasma exomal miR-1290 and miR-375 could be promising prognostic biomarkers for CRPC patients [47].…”