Current clinical issues in prostate cancer that can be addressed by imaging

Introduction

The role of imaging in the management of prostate cancer has long been controversial, and imaging continues to be both overused and underused. Guidelines are available regarding the use of imaging for the assessment of advanced disease.

However, in recent years, imaging technology has matured, image acquisition and interpretation have improved, and a host of clinical studies have demonstrated the potential of imaging for improving other aspects of prostate cancer care, including the detection of local primary or recurrent disease and surgical or radiation treatment planning.

This review will discuss the many ways in which imaging can contribute to the evidence-based clinical management of prostate cancer, focusing on the most commonly used cross-sectional imaging modalities: transrectal ultrasound (TRUS), computed tomography (CT), magnetic resonance imaging (MRI), radionuclide bone scanning, positron-emission tomography (PET), and combined PET/CT.

Imaging in diagnosis

Prostate-specific antigen (PSA) testing and digital rectal examination (DRE) continue to be the mainstays of prostate cancer detection. When either of these yields abnormal results, TRUS-guided biopsy is performed. The initial biopsy session will detect cancer in about 29% of patients who undergo biopsy for suspected prostate cancer, depending on the PSA level and DRE results.

However, the sensitivity for detection is about 80%-90%, depending on the biopsy scheme used [1, 2]. Cancers missed by systematic transrectal biopsy may be small or located in the anterior part of the gland, an area rarely sampled [3]. If repeated biopsies are negative in a patient at high risk for prostate cancer, MRI may be used to identify appropriate targets for an additional repeat biopsy [4]. Magnetic resonance imaging has been found to perform better than DRE in localizing cancer throughout the prostate gland and better than TRUS in localizing cancer in the middle and base of the gland [5]. It is also reasonably sensitive for detecting large cancers (>1 cm) in the anterior prostate gland [5].

Optimal MRI for prostate cancer detection requires the use of an endorectal coil and a pelvic phased-array coil on a mid- to high-field magnet, with thin (3 mm) slices and a small (14 cm) field of view [6]. On T₂-weighted MR images, the zonal anatomy of the prostate can be seen. Cancer most commonly demonstrates decreased signal intensity within the high-signal-intensity peripheral zone, but it may also be detected in the transition zone [7, 8]. New technology that allows co-registration of MRI with real-time TRUS to guide prostate biopsies appears promising [9].

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Hedvig Hricak and Peter T. Scardino
Prostate Cancer, eds. Hedvig Hricak and Peter T. Scardino. Published by Cambridge University Press.© Cambridge University Press 2009.