Samir Taneja, MD
The use of MRI scans to detect and treat prostate cancer more effectively continues to be a growing area of investigation, according to Samir Taneja, MD.
Researchers are investigating how MRI scans can more precisely target and stage aggressive disease, as well as clinically insignificant cancers. Prior data published in the Journal of Urology
showed that MRI-guided biopsies were 3 times as likely to identify cancer compared with traditional biopsies. MRI detected 38% of high-grade cancers that had been missed with a biopsy.
In an interview during the 2018 OncLive®
State of the Science SummitTM
on Genitourinary Cancers, Taneja, director, Urologic Oncology, Genito-Urologic program leader, NYU Langone’s Perlmutter Cancer Center, discussed his research on MRI-guided prostate biopsies and other modalities in development.
OncLive: Can you provide an overview of your presentation?
: My research really has focused on the idea of using imaging to change the way we diagnose the disease, risk-assess prostate cancer, select treatments, and even the way we've started to treat it in order to reduce some of the side effects that men experience when they go through conventional therapy. We started thinking we could see the cancer before we biopsy it, very similar to the way a woman gets a mammogram before she gets a biopsy.
With the advent of the multiparametric MRI, which allows us to use different functional sequences to better assess the prostate and determine what’s cancer and what’s not, we're able to localize cancers accurately. NYU Langone is one of the early innovators in the area of prebiopsy MRI of the prostate. We think we can monitor the disease better than we used to be able to with fewer biopsies.
Finally, we have used it to change the way we think about treatment. Whereas previously, we used to treat patients uniformly by removing the whole prostate or radiating the whole prostate. Now, we are trying to transition to a paradigm similar to a lumpectomy where we find the tumor, localize it, and then destroy it using some energy source—heat, freezing, or the like. We have very early data on the effectiveness of that, but it is the imaging that has empowered us to do it.
If you have an image in front of you, what are some characteristics to look for that determine how you are going to assess risk?
When we look at a prostate MRI, there are some basic functional sequences we look at. The first is what’s called the standard image, or the T2-weighted image. That's really an anatomic image that allows us to visualize the prostate at high resolution. We are looking for dark areas in the prostate that might represent cancer—essentially small, rounded areas or smudges through the cancer that look darker than the normal tissue.
The problem is that the sequence alone is very nonspecific; inflammation, scarring, and atrophy can cause a similar appearance to cancer on that T2-weighted image. We improve the accuracy and we reduce the false positive rate by adding functional sequences—one of which is called the diffusion-weighted image. Diffusion-weighted imaging is basically a method of measuring water movement in the tissue. Normal tissues allow passive movement of water molecules, but cancer, because it tends to be densely packed and higher pressure, restricts the movement of water. Restricted diffusion or restricted movement of water is another indicator of cancer. Now, if we see an area that’s dark on a T2-weighted image and there is a region of restricted diffusion, that increases our suspicion that there could be cancer.
Then, we look at perfusion images. We give gadolinium contrast to the patient and measure the rate at which the contrast accumulates in the area of suspicion and the rate at which it flows out. Cancers tend to accumulate contrast faster than normal tissues and lose contrast, or wash out, faster than normal tissues. By measuring that every 5 seconds and creating a curve, one can add additional information about suspicion.
Once we see that, the radiologist then assigns a score that assesses their suspicion level. We call that the PI-RADS score, which is now a nationally standardized 5-point scale created by the American College of Radiology that allows us to assess risk. A PI-RAD V classification would be almost definitely cancer. A PI-RAD I would be a normal MRI.