Dynamic Contrast-Enhanced MRI of Prostate Cancer

Prostate cancer is the most commonly diagnosed cancer in men in the United States of America with an estimated 198,000 new cases in 2001 (Greenlee et al. 2001). In the United Kingdom and the European Union, prostate cancer is the second most common cancer in men, with 20,000 new cases in the UK in 1997 (CRC 2001) and an estimated 134,000 new cases in the EU in 1996 (EUCAN). Substantial increases in incidence have been reported in recent years around the world, some of which can be attributed to frequent use of transurethral resection of the prostate (TURP) to treat symptoms of obstructive benign prostatic hyperplasia (BPH) and serum prostatespecifi c antigen (PSA) testing to screen for prostate cancer. While there is some debate on whether there is a real increase in incidence of prostate cancer, what is clear is that the population at risk (old men) continues to increase in size with lengthening of life expectancy. These factors make prostate cancer a large and growing healthcare problem for men. There are three major areas where imaging techniques may lead to improvements in the management of patients with suspected or proven prostate cancer (Thornbury et al. 2001). These are detection and localisation of early prostate cancer, identifi cation of men for whom treatment is likely to be curative and early detection of the site of recurrent disease: (1) Many men with a raised PSA level detected at screening do not have an underlying prostate cancer. Approximately 70%−80% of men do not have a prostate cancer diagnosed at the time of the raised PSA test but on long-term follow-up, 38% of men will develop prostate cancer if the presenting PSA lies between 4.1−10 ng/ml (Smith et al. 1996). (2) Once the diagnosis of cancer is made, it can be diffi cult to determine which patients will benefi t from treatment. The most appropriate treatment for localised prostate cancer remains controversial. Prostate cancer can be an indolent malignancy and yet contributes substantially to cancer mortality. Whilst a number of prognostic factors are recognised, new indices of biological activity are needed to help distinguish between clinically indolent and potentially life-threatening carcinomas (Bostwick et al. 2000). (3) Clinical evaluation of suspected recurrent cancer after radical local treatment can be challenging. An elevated PSA level may be the only evidence of treatment failure after local treatment. Determining the site of recurrence is important because men with an isolated local recurrence can benefi t from further treatments such as radiotherapy to a prostatectomy resection bed. The identifi cation of prostate cancer with a view to a targeted biopsy is the major current role for transrectal ultrasound (TRUS) (Clements 2001). Using TRUS, prostate cancer can be visualised as a hypoechoic lesion in the peripheral gland; however, lesions can appear hyperechoic or isoechoic. It should be noted that hypoechoic lesions in the peripheral gland are not necessarily cancers (41% are cancers overall, 52% if the PSA is raised and 71% if the PSA is raised with a palpable abnormality; Lee et al. 1989). With the increasing use of PSA screening there has been downward stage migration of diagnosed prostate cancer. As a result, it has become increasingly diffi cult CONTENTS