5032 Background: Detection of prostate-specific transcripts in blood has been associated with survival, but validated assays are lacking. We analytically validated a qPCR-based assay in CLIA environment to detect prostate cancer enhanced transcripts in whole blood and determine its prognostic significance relative to circulating tumor cell (CTC) enumeration. Methods: Blood was collected from patients with progressive CRPC in PAXgene tubes for total RNA extraction. Five genes overexpressed in prostate tissue, KLK3, KLK2, HOXB13, GRHL2, and FOXA1, were analyzed by RT-qPCR. Each qPCR-reaction was performed in 6 replicates and detection thresholds for each gene were chosen by receiver operator curve analysis. Detection rates were compared to enumeration using CellSearch in an independent data set of 97 CRPC patients and survival associations explored by concordance probability estimate (CPE). Results: Two or more genes were detected by qPCR 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%). Transcripts were detectable in 21% (11 of 52, 95% CI 8–35%) of patients with favorable CTC counts (≤4). Similar to CTC enumeration, transcript detection predicted overall survival in a proportional hazards model. The predictive accuracy of qPCR detection in combination with CTC enumeration had a CPE of 0.752 (SE=0.038). Conclusions: This validated RT-qPCR assay detects prostate-specific mRNA in whole blood in more patients than CellSearch, is prognostic for survival, and may assess patient risk in conjunction with CTC enumeration. Its clinical utility will be prospectively explored. Supported by NCI SPORE in Prostate Cancer (P50 CA92629); the Department of Defense Prostate Cancer Research Program; Prostate Cancer Foundation; Mr. William H. and Mrs. Alice Goodwin and the Commonwealth Foundation for Cancer Research and The Experimental Therapeutics Center; DoD Prostate Cancer Research Program Physician Research Award W81XWH-09-1-0307.
Nebraska Prostate Cancer Research Program