Prostate Imaging with Color Doppler Ultrasound

BY MARK SCHOLZ, MD

Prostate cancer is the most common form of cancer in men. While some types are life-threatening others are not.  Recently the media have been reporting on serious concerns that have surfaced about men with the benign forms of the disease undergoing unnecessary radical treatment.  PSA screening has been receiving most of the blame, but the real problem is over reliance on random needle biopsies performed by an aggressive medical community made up of surgeons.

Significance of an Elevated PSA
An elevated PSA can occur as a result of any physical alteration of the environment in the prostate-- recent sexual activity, infection, cancer, and gland enlargement (BPH). A modest elevation of PSA is medically nonspecific. As one man explained, “Think of the Check Engine light on the dashboard of your car. It’s significant if it is ON, but further specifics need to be determined before taking any action.”

Time for a Random Biopsy?
PSA elevation typically triggers an immediate 12-core random biopsy. Presently, over a million men are undergoing biopsy every year at a cost of billions of dollars. Unfortunately, low grade prostate cancer is so prevalent in the general male population that a random biopsy will find prostate cancer 20% of the time, even when PSA is normal. Obviously a great preponderance of all this “cancer” must be harmless. After all, historical death rates from prostate cancer before 1987, when PSA screening first became available, were only 3%.

Damn the Possible Side Effects, Treat it Anyway
Cancer is a frightening word. To many, it portends death. Therefore it’s hardly surprising that both doctors and patients swing into immediate action when the biopsy shows CANCER. Amending and tempering words such as “low grade” or “microscopic” seem to produce no soothing affect whatsoever on the instinctual fears generated by this venomous diagnosis.   Despite the universal agreement of hundreds of prostate experts at a consensus conference back in 2007 which concluded that low-grade prostate cancer can be safely monitored, 85% of all men diagnosed still throw caution to the wind and get treatment anyway.

Imaging is “Blind” to Small Low-Grade Cancers
Back when doctors regarded all types of prostate cancer as universally dangerous, prostate imaging, which is prone to miss small, low-grade lesions, was deemed inadequate. However, with our modern perspective, knowing that only larger, higher-grade lesions are clinically relevant, imaging makes perfect sense. There are two types of prostate imaging: High-resolution Color Doppler Ultrasound, which is the subject of this blog, and multiparametric 3-Tesla MRI which was the subject of my last blog.

Color Doppler Ultrasound Imaging
It’s no longer appropriate to needle the prostate multiple times with the outdated belief that it’s essential to diagnose every tiny prostate cancer.  Practically speaking, only prostate cancers large enough to be “seen” (with imaging) need to be considered. Color Doppler Ultrasound scanning of the prostate is performed by a physician in the doctor’s office. It is actually two scans in one: Standard “Grey Scale” imaging and Color Doppler imaging to detect areas of increased blood flow.  First, ultrasound enables accurate measurement of the gland size. Second, from a cancer point of view, imaging with Color Doppler has three possible outcomes:   

A)   Completely clear

B)   An overtly suspicious lesion is detected

C)   Ambiguous lesion(s) are detected

Targeted Rather than Random Biopsies
When an overtly suspicious lesion is detected, a targeted biopsy (a limited number of cores aimed directly at the lesion) is typically recommended. Lesions that are biopsy-negative or show low-grade cancer are simply monitored.  When high-grade disease is diagnosed, a process of further staging followed by pertinent counseling about the different treatment options is initiated.

When to Biopsy Ambiguous Lesions
Expert judgment, with appropriate attention to the individual patient characteristics, comes into play during a discussion between patient and doctor about whether or not to do a targeted biopsy. Color Doppler “sees” all sorts of things including scar tissue, areas of active prostatitis, and nodular areas from BPH. A follow-up scan in six months to see if a lesion shows further growth may be preferred to immediate biopsy.  Lesion characteristics that raise greatest concern tend to be located in the peripheral zone of the prostate, and include lesions over a centimeter, lesions that bulge the prostate capsule and lesions that have increased blood flow.  Targeted biopsy is advised more frequently in men who are younger, are more anxious about missing cancer, and in men with PSA levels higher than they “should be” relative to the size of their prostate. 

“Cross Checking” Ambiguous Lesions with Multiparametric MRI
Color Doppler Ultrasound and Multiparametric MRI (MP-MRI) are complementary. In our experience the imaging findings match. However in a minority of cases one imaging modality will illuminate a specific lesion substantially more clearly. Therefore, in ambiguous cases, a combination of both modalities increases confidence that high-grade cancer isn’t being overlooked. Doing a second imaging procedure with MP-MRI is often preferable to doing an immediate biopsy.  If subsequently a targeted biopsy is deemed necessary, the additional imaging information obtained from MP-MRI may further increase the accuracy of the targeted biopsy.

Color Doppler for Monitoring Low-Grade Cancer
These days’ experts advise men with low-grade prostate cancer to forgo surgery or radiation and monitor their condition with Active Surveillance. The most common protocol used presently is regular PSA testing and periodic random biopsy. However, multiple random biopsies are associated with discomfort and progressive risk of serious infections and impotence.  Sequential monitoring of small lesions with Color Doppler to determine if they are growing or stable is a far more logical approach than subjecting men to repeated biopsies.

Final Thoughts
Men with elevated PSA, who initially undergo a Color Doppler, rather than random biopsy, are often spared biopsy altogether if their scan is clear.  Men who do require biopsy will need far fewer cores taken because the biopsy is targeted to a specific lesion within the gland. Men on Active Surveillance and men who have undergone previous treatment with surgery, radiation, cryotherapy, HIFU or hormone blockade are also candidates for Color Doppler Ultrasound to determine how well they are responding to treatment.