SEATTLE-Improvements in standard imaging techniques may lead to
enhanced prostate cancer detection and local staging accuracy
in the near future, Gary Sudakoff, MD, said at the Pacific Northwest
Cancer Foundation Meeting on Transperi-neal Brachytherapy for
Early Stage Prostate Cancer. Such methods may include combining
color Doppler imaging with endorectal ultrasound (see image )
and using new types of coils with magnetic resonance imaging (MRI),
said Dr. Sudakoff, of the University of Chicago.
Traditionally, the digital rectal examination (DRE) has been the
cornerstone of the preoperative diagnosis, he said. However, this
technique has significant limitations. For example, many benign
entities, such as benign prostatic hypertrophy (BPH), calculi,
fibrosis, atrophy, infarc-tion, or cysts, are also palpable on
DRE and may mimic cancer. On the other hand, malignant tumors,
some significantly advanced, may not be palpable.
Dr. Sudakoff stressed that DRE should always be performed during
the routine physical examination and that it still plays a major
role in the diagnosis of early prostate pathology. But the combination
of DRE and PSA levels provides a more accurate initial screening.
If either is abnormal, then further evaluation with endorectal
ultrasound (ERUS) and needle biopsy is warranted.
Although ERUS can detect masses that are not palpable on DRE,
Dr. Sudakoff noted that it, too, has limitations. ERUS can detect
abnormalities in the prostate but cannot accurately discriminate
benign from malignant lesions.
Furthermore, he said, ERUS is limited in local staging of prostate
cancers with accuracies approaching only about 60%. Another drawback:
ERUS is a highly subjective and operator-dependent technique,
and it may be less accurate in the hands of a less experienced
Thus, ERUS can be an excellent modality for use in detecting potential
cancers and directing biopsy of these lesions, but because of
its expense and limited accuracy, it should not be used alone
for prostate cancer screening, he said.
Color Doppler Imaging
The lack of specificity of "gray scale" ERUS has recently
been addressed with the development of color Doppler imaging.
This technique allows the detection of both normal and abnormal
vascular flow within tissue seen real-time during an ultrasound
Cancers generally have abnormal vascular flow patterns and appear
hyper-vascular compared to surrounding, normal tissue during color
Doppler imaging. While most prostate cancers are typically hypoechoic,
some may appear isoechoic and are not identifiable with gray scale
ultrasound. These patients may be correctly identified with color
Doppler during ERUS (see images ). Color Doppler imaging may then
be used to further direct biopsy in these patients.
In addition, color Doppler can be used to improve discrimination
between postsurgical scarring and recurrent or residual cancer
in patients who are status post-prostatectomy, he said (see figure).
In an ongoing clinical study at the University of Chicago, ERUS
alone correctly identified recurrent cancer with an accuracy of
approximately 60%. Color Doppler alone had an accuracy of approximately
70%. Using a combined approach of ERUS with color Doppler yielded
an accuracy of approximately 80%.
While preliminary, these data suggest that color Doppler imaging
may play an important role in patients with a rising PSA who are
status post-radical prosta-tectomy in detecting recurrent or residual
carcinoma in the prostate fossa.
Recent improvements in computer software and receiver coils are
greatly enhancing the accuracy of MRI in the diagnosis of prostate
cancer, Dr. Sudakoff said. Because of its high soft-tissue contrast
and multiplanar capability, MRI can be used to obtain a clear
visual image of the prostate.
With the use of endorectal and phase array pelvic surface receiver
coils, combined with an imaging technique known as fat suppression,
MRI can often detect the site and extent of a prostate cancer.
In particular, the ability to identify the prostatic capsule and
capsular invasion into periprostatic fat or the seminal vesicle
is now possible with accuracy rates reported between 70% and 85%.
In Dr. Sudakoff's opinion, MRI using these enhancement techniques
is currently the best technique for noninvasive staging of prostate