前立腺生検における生検前MRI の有用性についての検討

Abstract

We examined the value of pre-biopsy magnetic resonance imaging (MRI) for detecting prostate cancer. We analyzed 267 men with prostate-specific antigen (PSA) levels of 3-10 ng/ml who underwent systematic prostate needle biopsy. From April 2009 to March 2011, a total of 98 male patients underwent 16-core prostatic biopsies without pre-biopsy magnetic resonance imaging (MRI) (nonenforcement group). From April 2011 to March 2013, 169 men underwent pre-biopsy MRI [T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI)] (enforcement group). When MRI findings indicated cancer in the latter group, in addition to the systematic 16-core biopsy one or two targeted biopsies were performed. Patients without suspicious MRI findings underwent only systematic 16-core biopsy. Cancer detection rates in the nonenforcement andenforcement groups were 42.9% (48/92) and46. 2% (78/169), respectively. The difference did not reach significance (p＝0.612). Although the cancer detection rates were 39.4% (41/104) in the MRI-negative group and56. 9% (37/65) in the MRI-positive group (p＝0.039), the sensitivity and specificity for cancer detection by MRI were relatively low : 47.4% and 69.2%, respectively. By receiveroperating curve analysis, the area under the curve for cancer detection by MRI was only 0.583. There were two study limitations. First, the patient sample size was small. Second, it is unclear whether an adequate sample of the suspicious lesion was obtained by biopsy. We thus demonstrated that it might be improper to base a diagnosis solely on pre-biopsy MRI (T2WI and DWI) findings in men with serum PSA levels of 3-10 ng/ml.