Caveolin‐1 expression is a predictor of recurrence‐free survival in pT2N0 prostate carcinoma diagnosed in Japanese patients

BACKGROUND The authors previously identified elevated caveolin‐1 expression in human prostate carcinoma and determined that caveolin‐1 levels as detected by immunohistochemistry of radical prostatectomy specimens offered novel prognostic information. A higher incidence of caveolin‐1 expression also was reported in African‐American men compared with white men in the U.S. To explore these ethnic/racial differences in caveolin‐1 expression further, the authors evaluated caveolin‐1 expression as a predictive marker in Japanese men with prostate carcinoma. METHODS Immunohistochemical staining with a caveolin‐1 specific antibody was performed on routinely processed paraffin sections from 152 consecutively collected radical prostatectomy specimens. The mean patient age was 64.3 years (range, 49–74 years; median, 64.5 years) and the mean follow‐up period was 49.5 months (range, 1.3–103.3 months; median, 48.2 months). Caveolin‐1 immunoreactivity was evaluated in association with patient's age; preoperative prostate specific antigen level; clinical stage; and pathologic features including Gleason score, extraprostatic extension, status of surgical margins, seminal vesicle involvement, lymph node involvement, and time to disease progression after surgery. RESULTS Positive caveolin‐1 immunostaining was detected in 46 of the 152 tumors (30.3%) and was found to be associated significantly with a positive surgical margin (P = 0.022). A higher incidence of caveolin‐1 expression tended to be found in patients with poorly differentiated tumors (Gleason score > 7, 6–7, and < 6, 35.0% vs. 34.9% vs. 20.4%, respectively) or in patients with extraprostatic extension versus those without extraprostatic extension (35.4% vs. 24.7%) or patients with lymph node involvement compared with those without lymph node involvement (50% vs. 29.5%), although these differences did not reach statistical significance (P = 0.100, P = 0.150, and P = 0.178, respectively, by the Spearman correlation test). Kaplan–Meier analysis revealed that increased caveolin‐1 expression was associated with an increased risk of disease progression at 5 years (P = 0.0122 by the log‐rank test). In patients with organ‐confined (pT2N0) disease, univariate Cox proportional hazards regression analysis revealed that positive caveolin‐1 expression was the only significant predictor of disease recurrence after radical prostatectomy (P = 0.011; hazards ratio = 4.75; and 95% confidence interval, 1.43–15.76). CONCLUSIONS The r