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 results of the current study confirm that positive caveolin-1 expression is associated with clinical markers of disease progression and is predictive of poor clinical outcome after surgery in Japanese patients with pT2N0 prostate carcinoma.