PSA40ng/ml以下の前立腺癌の全摘標本の検討と長期のPSA推移

Abstract

前立腺全摘除術132例中31例(23%, 平均年齢65.4歳)に認めた前立腺特異抗原(PSA)≦4のPSA低値癌とPSA>4の101例(平均年齢65.7歳)の病理組織を比較し, 癌発見までのPSA推移について検討した。全摘標本の病理結果ではpT2, 被膜外浸潤, 精嚢浸潤, リンパ節転移の割合はいずれも有意差を認めなかった。直腸内触診(DRE)陽性率はPSA低値癌症例が20%に対しPSA>4症例は44%であり, PSA低値癌で有意にT1c癌を多く認めたが, 精嚢浸潤を認めた3例はすべてDRE陽性であった。癌診断前に1年以上PSA値を複数回測定したPSA低値癌症例の19例のうち74%が, PSA変化率0.50ng/ml/yearかつPSA倍加時間4年未満であった。「PSA値がその個人において以前確認された値に戻らない」という相対的異常は生検適応基準の1つの目安と考えられる。

Out of 132 prostate cancer (Pca) patients who underwent radical prostatectomy 31 (mean age 65 +/- 5 years) had prostate specific antigen (PSA) levels of 4.0 ng/ml or less (low PSA group). The average PSA level was 3.3 +/- 0.5 ng/ml in the low PSA group and 8.5 +/- 5.5 ng/ml in patients with a higher PSA (high PSA group). The pT2 ratio of the radical prostatectomy specimens was 74% (23/31) in the low PSA group and 55% (55/101) in the high PSA group, pT3a was 16% (5/31) and 31% (31/101), pT3b was 10% (3/31) and 10% (10/101), pN1 was 0% and 5% (5/101), respectively. The digital rectal examination (DRE) gave a positive result significantly (p = 0.026) less frequently in the low PSA group (6/31 : 20%), than in the high PSA group (44/101 : 44%). However all three pT3b patients with a low PSA were positive in DRE. This suggests the importance of DRE to detect significant Pca with PSA < or = 4.0. PSA was measured at least three times for more than one year in 19 of the 31 patients with a low PSA level before diagnosis. In 14 of these 19 cases (74%), PSA velocity was more than 0.5 ng/ml/ year and PSA doubling time was less than 4 years. Some patients with significant Pca can not be detected with a PSA cutoff level at 4.0 ng/ml. We recommend that individuals have their own PSA levels, and that long-term changes of PSA are sometimes very important to detect cases of Pca with lower PSA.