I RECENTLY REVIEWED A CONTINUING MEDICAL EDUCATION COURSE ON USING MRI IMAGING FOR DIAGNOSIS AND TREATMENT OF PROSTATE CANCER BY UROLOGISTS FROM STANFORD AND UCLA.
Why review this?
Prostate cancer is the second most deadly cancer in men. 250,000 new cases are diagnosed per year and 30,000 men die of prostate cancer per year. These numbers tell us two things:
1) Many more men are diagnosed than are dying of prostate cancer.
2) We are either doing a great job of treating prostate cancer, or we are diagnosing too many men.
The PSA screening test (prostate specific antigen) has been much maligned by the government. But, the truth is that we have decreased death from prostate cancer by 70% in the last 20 years and those numbers are mostly due to better early detection with the PSA test.
Now, our task is to make sure that we are not over treating men.
All urologists know that the most important task in providing personalized care for the man with potential prostate cancer is to determine if that man has the more benign low risk form of prostate cancer or if the deadly high risk form of cancer is present.
The diligent urologist is forever searching for the “holy grail” of the perfect test to help us decide how aggressive we need to be with an individual patient. So far, there is no perfect test. But, great progress has been made.
MRI (magnetic resonance imaging) is giving us more useful information than any other imaging modality.
What is MRI?
“When placed in the strong magnetic field of an MRI scanner, the protons of hydrogen atoms in your tissue align with the magnetic field. Radio frequency pulses applied to that field produce images that the radiologist can review when the protons are displaced by this alignment.”
Confused already? Don’t be. You just need to have gone to MIT or Georgia Tech to fully understand.
All teasing aside; you are placed in a magnetic field, radio waves are applied in pulses and your protons in your hydrogen cells are able to give off a signal that can be visually detected. By applying different “weighting” to the signal, more specific information can be elucidated from the images. Your radiologist will use terms like T-2 weighting, dynamic contrast enhanced imaging and diffusion-weighted imaging. All of these methods of manipulating the pulse and images lead to greater in-depth information of your prostate anatomy.
All the patient has to do is be very still during the test! (and get your insurance company to pay for the technology)
Prostate cancer occurs most commonly on the outside part of the prostate. That is why the urologist always does a rectal exam. The rectal side of the prostate is where most cancers reside. By using the three above mentioned techniques, your urologist and radiologist can determine much more about your prostate than we can learn with ultrasound or CAT scan or PET scanning.
As you might imagine, the ability to get this information will be determined by the quality of the MRI equipment used, and the knowledge of the MRI radiologist reading the study and the coordination of detailed information provided by your urologist.
As in all radiology tests, there are conditions that can make the test less accurate. Prostatitis, benign prostatic hypertrophy, post radiation, post surgery, post biopsy and hormone ablation must all be taken into consideration when interpreting your MRI.
To help you understand how an MRI could give a tissue diagnosis, you must know a little of tumor biology. Cancers, particularly high grade cancers, typically have higher cell density and more complex microstructure that restricts diffusion of water .In simple terms, cancer cells tend to be more disorganized and clump together and be more chaotic than normal tissue. This phenomenon is detected as a bright white image on one type of MRI signal. So by manipulating the characteristics of the MRI signal, the radiologist can get information about the types of cells that might be in your prostate. AMAZING!!
MRI, CT AND PET SCANS CAN ALL GIVE INFORMATION ABOUT LOCAL SPREAD OF PROSTATE CANCER AND LYMPH NODE INVOLVEMENT OF PROSTATE CANCER. But, only MRI can come close to helping determine cancer from non-cancer and low grade cancer from high grade cancer.
I don’t want to give you a headache, but what I have included here is a very simplistic overview of what MRI can do. The radiologist can inject many types of biologically active compounds into your blood stream that can be taken up by different types of cells and can give us even more information.
So, how could YOU and Dr. BOONE use this information?
We know that if 250,000 new cases of prostate cancer are being diagnosed every year and 30,000 men are dying every year; there is definitely some over treatment and over diagnosis going on.
We do NOT want to go back to the pre PSA era when 70% more men died of prostate cancer. But, we also don’t want to put too many men at risk with over treatment either.
So, in summary:
MRI is an evolving tool to help us determine what personalized care is best for the individual man with risk for prostate cancer. No longer does “one size fit all.”
At this juncture, MRI cannot replace biopsy. Most men still need yearly rectal exam, yearly PSA testing and most men with abnormalities will still need biopsy. But, we do have an exciting and evolving technology that when applied by experienced radiologists with excellent MRI equipment can help us in determining the details of your care.
God bless those smart engineers who never get any of the credit!!