前立腺癌に対するネオアジュバントホルモン療法後のMRIによる原発巣局在診断

Abstract

1998年4月以降にネオアジュバントホルモン療法(NAH)後に前立腺全摘術を施行した限局性前立腺癌21例(51～75歳)を対象とした.MRIによりdown stageと判定した4例のうち全摘標本病理診断と一致した例は2例であった.一方, NAH後のMRIでT2以下と診断した症例のうち, 全摘標本病理診断がT3であった場合をunderdiagnosisとすると, 5例(23.8%)にunderdiagnosisを認めた.NAH後のMRI診断によるT stageのaccuracyは71%であった.NAH期間が7ヵ月以内の17例におけるaccuracyは64%であった.被膜外浸潤と精嚢浸潤のaccuracy, sensitivity及びspecificityは, 各々76%, 0%, 94%, 及び85%, 0%, 100%であった

We retrospectively studied the staging accuracy of magnetic resonance (MR) imaging after neoadjuvant hormonal therapy (NAH) for 21 localized prostate cancers. MR imaging was performed using a 1.5-Tesla magnetic resonance system with a pelvic phased array coil. T2-weighted MR images were obtained on axial and coronal planes, and T1-weighted MR images using the dynamic technique with Gd-DTPA bolus enhancement were obtained in axial planes for each patient. On T2-weighted imaging, the signal intensity of the normal tissue in the peripheral zone became lower after NAH. Therefore, it was more difficult to detect residual malignant lesions in many cases than before NAH. The accuracy of T staging for prostate cancer after NAH in MRI was 71%. The accuracy, sensitivity, and specificity of the extracapsular invasion was 76%, 0% and 94%, respectively, and those of the seminal vesicular invasion 85%, 0% and 100%, respectively. While 2 of the 4 patients judged as downstaged cases in MRI showed corresponding pathological findings, 5 of the 21 cases (23.8%) were underdiagnosed. Local staging with only MRI for prostate cancer after NAH seems to have limits in applicability.