[967] Comparison of Latent Prostate Cancer Detected at Autopsy between Pre- and Post-Prostatic Specific Antigen (PSA) Era

Mioko Okayasu, Hiroyuki Takahashi, Bungo Furusato, Masato Kido, Sainosuke Mizukami, Masakuni Furusato, Hiroshi Hano. The Jikei University School of Medicine, Minato-ku, Tokyo, Japan

Background: The prevalence of latent prostate cancer (LPC) found only at autopsy has been explored only in relatively old reports (from the 1980s and 1990s) in Asian prostate cancer research. The LPC has been widely recognized as well differentiated microscopic cancer. To determine whether significant differences now exist in LPC between periods before and after the advent of serum PSA screening for Asian prostate cancer detection, we compared 2 groups of men undergoing autopsy during the 2 periods.
Design: The Jikei University institutional autopsy records were searched for cases that had undergone prostate dissection at autopsy to identify prostate cancer. A total of 500 men were available between 1983 and 1992 (cohort A), and 89 men were available between 2009 and 2011 (cohort B) for this study. We calculated the incidence of LPC and compared the pathological parameters, including grade distribution and the proportion of tumor volume (TV) between the 2 cohorts. In addition, the frequency of phosphorylated AKT (pAKT) expression in cohort B was analyzed by immunohistochemistry.
Results: In cohort A, the prevalence of LPC was 22% (104/500 cases) compared with 40% (36/89 cases) in cohort B. In cohort A, the average TV was 230.4mm3 (range: 4.8-18,463mm3), which increased to 1280.02 mm3 (range: 0.5-19,091.2 mm3) in cohort B. Cases showing significant TV (>500 mm3) accounted for only 9.6% in cohort A, but increased to 22.2% (8/36) in cohort B. There was no trend observed in the grade distribution between the 2 cohorts. In addition, the expression of pAKT was detected in 12/26 available cases (46.2%) of cohort B, the incidence was quite similar to clinically detected prostate cancer (49%: our data from the Japanese cases). Expression of pAKT was detected in 100% (6/6) of the cases with TV>500 mm3, and in 30% (6/20 cases) with TV<500mm3 in cohort B, respectively (p=0.0026).
Conclusions: In recent years, autopsy rates have been decreasing at our institution. Though PSA screening has become standard, the prevalence and TV of LPC have increased quite dramatically in Japan, which may raises questions about the usage of PSA screening. We also found that certain percentage of LPC seems to be similar to the clinical cancer, especially in the post-PSA cohort (i.e. from its size and the cancer-related protein expression). Therefore, further studies are required to determine whether this finding is reproducible in multi-institutional analysis and clinically important.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 171, Wednesday Afternoon


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