Color Doppler, MRI Hold Promise for Improved Detection of

October 1, 1995

SEATTLE-Improvements in standard imaging techniques may lead toenhanced prostate cancer detection and local staging accuracyin the near future, Gary Sudakoff, MD, said at the Pacific NorthwestCancer Foundation Meeting on Transperi-neal Brachytherapy forEarly Stage Prostate Cancer. Such methods may include combiningcolor 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.

SEATTLE-Improvements in standard imaging techniques may lead toenhanced prostate cancer detection and local staging accuracyin the near future, Gary Sudakoff, MD, said at the Pacific NorthwestCancer Foundation Meeting on Transperi-neal Brachytherapy forEarly Stage Prostate Cancer. Such methods may include combiningcolor 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 thecornerstone of the preoperative diagnosis, he said. However, thistechnique has significant limitations. For example, many benignentities, such as benign prostatic hypertrophy (BPH), calculi,fibrosis, atrophy, infarc-tion, or cysts, are also palpable onDRE 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 duringthe routine physical examination and that it still plays a majorrole in the diagnosis of early prostate pathology. But the combinationof DRE and PSA levels provides a more accurate initial screening.If either is abnormal, then further evaluation with endorectalultrasound (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 detectabnormalities in the prostate but cannot accurately discriminatebenign from malignant lesions.

Furthermore, he said, ERUS is limited in local staging of prostatecancers 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 experiencedexaminer.

Thus, ERUS can be an excellent modality for use in detecting potentialcancers and directing biopsy of these lesions, but because ofits expense and limited accuracy, it should not be used alonefor prostate cancer screening, he said.

Color Doppler Imaging

The lack of specificity of "gray scale" ERUS has recentlybeen addressed with the development of color Doppler imaging.This technique allows the detection of both normal and abnormalvascular flow within tissue seen real-time during an ultrasoundexamination.

Cancers generally have abnormal vascular flow patterns and appearhyper-vascular compared to surrounding, normal tissue during colorDoppler imaging. While most prostate cancers are typically hypoechoic,some may appear isoechoic and are not identifiable with gray scaleultrasound. These patients may be correctly identified with colorDoppler during ERUS (see images ). Color Doppler imaging may thenbe used to further direct biopsy in these patients.

In addition, color Doppler can be used to improve discriminationbetween postsurgical scarring and recurrent or residual cancerin patients who are status post-prostatectomy, he said (see figure).

In an ongoing clinical study at the University of Chicago, ERUSalone correctly identified recurrent cancer with an accuracy ofapproximately 60%. Color Doppler alone had an accuracy of approximately70%. Using a combined approach of ERUS with color Doppler yieldedan accuracy of approximately 80%.

While preliminary, these data suggest that color Doppler imagingmay play an important role in patients with a rising PSA who arestatus post-radical prosta-tectomy in detecting recurrent or residualcarcinoma in the prostate fossa.

Recent improvements in computer software and receiver coils aregreatly enhancing the accuracy of MRI in the diagnosis of prostatecancer, Dr. Sudakoff said. Because of its high soft-tissue contrastand multiplanar capability, MRI can be used to obtain a clearvisual image of the prostate.

With the use of endorectal and phase array pelvic surface receivercoils, 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 andcapsular invasion into periprostatic fat or the seminal vesicleis now possible with accuracy rates reported between 70% and 85%.

In Dr. Sudakoff's opinion, MRI using these enhancement techniquesis currently the best technique for noninvasive staging of prostatecancer.