Association of SPARC expression with metastatic progression and prostate cancer-specific mortality after radical prostatectomy.

Abstract

5071 Background: We assessed the expression of the glycoprotein SPARC (secreted protein, acidic, rich in cysteine) in patients with prostate cancer (PCa) treated with radical prostatectomy (RP) and studied its association with adverse clinico-pathological features at RP and long-term clinical outcomes, such as metastatic progression after surgery and cancer-specific death. Methods: Tissues from 78 patients with PCa were used to quantify SPARC expression using tissue microarray (TMA) and immunohistochemistry techniques (IHC). Anti-SPARC mouse monoclonal antibody were use to target the protein and for each patients 4 samples of tissue were used for cytoplasmic staining. Staining of each core was reviewed by an uropathologist who assigned a score (score 0-3) to each core and a global score also assigned to each patient (score 0-3). Analyses of the data relied in cross tables, T-test analyses, survival plots and Cox regression models. Results: Higher expression of SPARC protein was recorded in patients who develop metastases during follow-up after RP (p=0.025) and in patients who died of PCa after RP (p=0.002). Median follow-up of the cohort was 9.3 years after RP. At 5 years, 95.5%, 92.0% and 89.3% of patients were metastases-free for SPARC expression score 1, 2 and 3 respectively. For the same categories, 10 years after RP, 82.2%, 77.0% and 69.9% were metastases-free (Log-rank tests all p≤0.05). Similarly, patients with high SPARC expression had worse cancer-specific survival at 5 and 10 years after RP compared to those with low SPARC expression (Log-rank tests all p≤0.01 when score 1 was compared to score 2 or score 3). Finally, advanced stage at RP (T3-T4) [p=0.04] and high Gleason sum (8-10) [p=0.02] were also associated with higher expression of SPARC. Conclusions: High SPARC expression was associated with worse outcomes in men with prostate cancer treated with radical prostatectomy. Men who developed metastatic disease and men who succumbed to prostate cancer had higher levels of SPARC at radical prostatectomy than their counterpart. SPARC may have an important role in the progression of the disease and may eventually help clinician to better ascertain the risk of progression of the disease.