前立腺癌血清マーカーとしてのProstate-specific Antigen(PA)の臨床的評価

Abstract

前立腺癌の未治療例23例, 既治療例33例を含む種々泌尿器疾患235症例を対象に, 血清PAと前立腺酸性フォスファターゼ(PAP)の同一血清での測定を行なった.血清PAのcut off levelは, 前立腺肥大症のmean+2SDである24.7 ng/ml, PAPのcut off levelは3.1 ng/mlとした.PA値のみでの前立腺癌検出率は57%, PAP値のみでの検出率52%であったが, 両値のいずれかが陽性の組み合わせにより検出率は65%となった.両値がともに陽性の組み合わせでは検出率は43%と劣化するが, 検出精度は100%となった.なお, γ-seminoprotein及びPA各測定のkit中の抗原スタンダードサンプルを用い, 互いのkitの交叉測定を行なったところ, いずれにも直線性が認められたことより, 両者は共通の抗原決定基を有すると考えられた

Combined measurement of serum prostate-specific antigen (PA) and prostatic acid phosphatase (PAP) was performed in 235 patients with various urologic diseases including 55 patients with prostatic cancer. A PA level of over 24.7 ng/ml and a PAP level of over 3.1 ng/ml were considered to be positive. The positive rate of PA was 57% in the patients with untreated prostatic cancer and 3% in the patients without prostatic cancer. The positive rate of PAP was 52% in the patients with untreated prostatic cancer and 1% in the patients without prostatic cancer. PA and PAP were considered to be equally sensitive and specific serum markers of prostatic cancer. However, the positive rate increased to 65% without increasing the false positive rate when the PA and PAP were both measured simultaneously. The combined assay of PA and PAP is recommended for screening prostatic cancer. The cross-over titer of PA and gamma-Sm using standard samples in each kit revealed linearity, which suggested that PA and gamma-Sm possess the same antigenicity.