The Terry Fox Research Institute Canadian Prostate Cancer Biomarker Network: an analysis of a pan-Canadian multi-center cohort for biomarker validation

Abstract

Background: Refinement of parameters defining prostate cancer (PC) prognosis are urgently needed to identify patients with indolent versus aggressive disease. The Canadian Prostate Cancer Biomaker Network (CPCBN) consists of researchers from four Canadian provinces to create a validation cohort to address issues dealing with PC diagnosis and management.

Methods: A total of 1512 radical prostatectomy (RP) specimens from five different biorepositories affiliated with teaching hospitals were selected to constitute the cohort. Tumoral and adjacent benign tissues were arrayed on tissue microarrays (TMAs). A patient clinical database was developed and includes data on diagnosis, treatment and clinical outcome.

Results: Mean age at diagnosis of patients in the cohort was 61 years. Of these patients, 31% had a low grade (≤6) Gleason score (GS), 55% had GS 7 (40% of 3 + 4 and 15% of 4 + 3) and 14% had high GS (≥8) PC. The median follow-up of the cohort was 113 months. A total of 34% had a biochemical relapse, 4% developed bone metastasis and 3% of patients died from PC while 9% died of other causes. Pathological review of the TMAs confirmed the presence of tumor and benign tissue cores for > 94% of patients. Immunohistochemistry and FISH analyses, performed on a small set of specimens, showed high quality results and no biorepository-specific bias.

Conclusions: The CPCBN RP cohort is representative of real world PC disease observed in the Canadian population. The frequency of biochemical relapse and bone metastasis as events allows for a precise assessment of the prognostic value of biomarkers. This resource is available, in a step-wise manner, for researchers who intend to validate prognostic biomarkers in PC. Combining multiple biomarkers with clinical and pathologic parameters that are predictive of outcome will aid in clinical decision-making for patients treated for PC.

Keywords: Biomarker validation; Immunohistochemistry; Patient prognosis; Prostate cancer; Tissue microarray.

Fig. 1

Design of the CPCBN Validation Tissue Microarray Platform for Prostate Cancer Biomarkers

Fig. 2

Immunohistochemistry and hierarchal clustering analysis of biobanked specimens arrayed in the QC-TMA, representing 50 radical prostatectomy cases from five different centres (total of 150 cores). a IHC evaluation with nine protein tissue markers. b Hierarchal clustering based on IHC detection of the nine different markers in samples of different center origin, corresponding to the colour legend below

Fig. 3

Fluorescence in-situ hybridization of the QC-TMA, with DNA probes detecting PTEN (orange), WAPAL (green), FAS (aqua), and CEP 10 (red). a Cells representing no PTEN deletion. b Cells showing homozygous PTEN deletion with relative hemizygous loss of WAPAL and FAS signal. c Cells in the same gland showing homozygous (Homo) and hemizygous (Hemi) PTEN deletions. d PTEN deletion status among the 50 patients in the QC-TMA. e Overall quality assessment of 150 cores for FISH analysis. Intermediate quality was assigned to 53% of cores that had a detectable PTEN deletion status but also had high background to signal ratios or had areas that were over-digested. Very good quality was observed for 34% of cores that produced strong signal over low background and even digestion throughout (Additional file 2)

Fig. 4

Kaplan-Meier plots showing relationship of clinical parameters with biochemical relapse (BCR). Both cohort of patients, Test (a-d) and Validation (e-h), were assessed independently. Clinical parameter evaluated were PSA level prior to surgery (a, e), pTNM (b, f), Gleason grade (c, g) and margin status (d, h). Statistical significance was set at p < 0.05