With prostate cancer the second most common non-skin cancer, medical imaging modalities
play a critical role in detection and treatment. Transrectal ultrasonography, MR imaging
and MR spectroscopy are among the key tools used to diagnose and treat prostate cancer.
Prostate adenocarcinoma is the
second most common non-skin cancer, and the second most common cause of cancer death in
men in the U.S. — with 198,100 new cases and 31,500 deaths being forecast for 2001.1
A white man has a 13.8 percent risk and a black man a 12.5 percent risk of having prostate
cancer diagnosed during his lifetime.2 Approximately 70 percent of prostate
cancers form in the peripheral zone. The unique metabolism of this tissue leads to the
synthesis and secretion of large amounts of citrate. The transition zone, which is the
site of benign prostatic hyperplasia, accounts for 20 percent of prostate cancers and the
central zone for only 10 percent.
The management of prostate cancer is determined by the
stage and grade* of the tumor and the serum concentration of prostate specific antigen
(PSA) (see box page 62). Imaging is important in determining stage, in directing biopsies
to confirm the presence of cancer and assess its grade, and in many current forms of
management.
Does he have cancer?
Transrectal ultrasonography (TRUS), often in a urologist’s office, is the standard
method of imaging possible prostate cancer. The examination is performed in the axial and
sagittal planes with a high-frequency transducer, and the volume of the gland is
estimated.4,5
Unfortunately, prostate cancer does not produce predictable sonographic changes.
Between 60 percent and 70 percent of these cancers are hypoechoic, but some benign
conditions also produce hypoechoic areas, and the positive predictive value (PPV) of this
finding is no greater than 52 percent.4 As
many as 40 percent of prostate cancers are isoechoic and thus invisible by TRUS.4 Moreover, only tumors in the peripheral zone
can be imaged reliably.4 The deficiencies
of the examination were summarized with the comment that “specificity and sensitivity
of conventional grey-scale TRUS for the detection of prostate cancer are disappointingly
low.”6 However, TRUS is critical to
accurate tissue sampling during biopsy.7
Abnormal areas are sampled, and sextant biopsies are acquired to ensure examination of all
areas of the gland.
Please refer to the October 2002
issue for the complete story.
For information on article reprints, contact
Martin St. Denis
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