MR-IMAGING AND SONOGRAPHY OF EARLY PROSTATIC-CANCER - PATHOLOGICAL AND IMAGING FEATURES THAT INFLUENCE IDENTIFICATION AND DIAGNOSIS

OBJECTIVE. The purpose of this study was to correlate findings at MR i maging and transrectal sonography with histopathologic findings after surgery in patients with prostatic cancer, to identify the pathologic characteristics of prostatic cancer that improved detection with MR im aging and transrectal sonography, and to identify the imaging characte ristics that correlated with detection of true cancers. MATERIALS AND METHODS. Data from MR imaging in 320 patients and from transrectal son ography in 343 patients who were enrolled in the Radiological Diagnost ic Oncology Group multiinstitutional study of imaging in prostatic can cer were correlated with results of radical prostatectomy. Only cancer s 5 mm or greater in at least one dimension were evaluated pathologica lly. The locations of lesions and the linear dimensions and volumes of individual lesions and the prostate gland were evaluated pathological ly and with imaging studies. The appearance of lesion margins on image s and the degree of differentiation of lesions seen on pathologic exam ination were also studied. Univariate and multivariate analyses were p erformed to determine the pathologic findings associated with imaging detection and the imaging characteristics associated with prostatic ca ncer. RESULTS. MR imaging and transrectal sonography showed 62% and 64 % of cancers, respectively, each with a positive predictive value of 6 8%. Cancers that were larger, moderately or poorly differentiated, or located in the posterior half of the outer gland were easier to detect (p < .0001). The overall size of the prostate did not affect lesion d etection. However, abnormalities identified in the posterior half of t he outer gland were more likely to be cancers. On transrectal sonogram s, larger abnormalities also were more likely to be malignant tumors. The sharpness of the margins of the imaged abnormalities did not predi ct pathologic status. CONCLUSION. Detection of prostatic cancer with M R imaging or transrectal sonography is affected by cancer size, differ entiation, and location; the odds of an imaged lesion's being malignan t are related to location and, for transrectal sonography, size. Knowl edge of anatomic/pathologic features that enhance lesion detection may help when using imaging tests to detect prostatic carcinoma. That cer tain imaging characteristics of lesions are associated with true cance rs may assist in the interpretation of MR images and transrectal sonog rams of the prostate.