SPINK1 expression and outcomes postprostatectomy in race-specific cohorts.

Abstract

23 Background: The SPINK1 molecular subtype has been shown to be more common in African American (AA) men with prostatic adenocarcinoma (PCa) than European Americans (EA). Other studies have suggested that SPINK1 expression is associated with more aggressive disease. However, there have been limited studies examining clinical outcomes by SPINK1 status in racially diverse cohorts. Methods: The objective was to determine the associations between SPINK1 subtype, race, and clinical and pathologic outcomes after radical prostatectomy (RP). A total of 186 AA and 206 EA men who underwent RP at Johns Hopkins were matched according to pathologic Gleason grade. We examined SPINK1 status by immunohistochemistry on tissue microarrays using a genetically validated assay. ERG and PTEN were assessed previously using validated immunohistochemistry assays. SPINK1 prevalence was compared between races. Logistic regression and Cox proportional hazard analyses assessed the association of SPINK1 status with pathologic and oncologic outcomes in race-specific multivariate models. Results: SPINK1-positive subtype was present in 25% (45/186) of AA and 15% (30/206) of EA men (p = 0.013). SPINK1 expression was generally mutually exclusive with ERG expression and PTEN loss in both racial cohorts. There were no differences in pathologic grade group (GG), pathologic stage, biochemical recurrence (BCR)-free survival, or metastasis-free survival between SPINK1-positive and SPINK1-negative tumors in the overall cohort or by race. In multivariable analyses, SPINK1 expression was not associated with BCR (AA: HR 0.99, 95% CI 0.56-1.75, p = 0.976; EA: HR 0.88, 95% CI 0.43-1.77, p = 0.720) or metastasis (AA: HR 0.79, 95% CI 0.25-2.49, p = 0.691; EA: HR 1.55, 95% CI 0.58-4.11, p = 0.381) in either the AA or the EA cohort. Conclusions: SPINK1-positive subtype is more prevalent in AA than EA men with PCa. While previous studies showed that SPINK1 may be associated with more aggressive PCa, we found that SPINK1 protein expression was not associated with worse pathologic or oncologic outcomes including BCR and metastasis after RP in either AA men or EA men.