Multiparametric Magnetic Resonance Imaging Staging Exam Better Characterizes Prostate Cancer
The following article was written by John Kurhanewicz, Ph.D., Professor in the Department of Radiology and Biomedical Imaging and Director of the Prostate Cancer Imaging Group at UCSF.
UCSF’s world-renowned expertise in prostate cancer and spectroscopic imaging has led our Prostate Cancer Imaging Group to develop a multiparametric magnetic resonance imaging staging exam of prostate cancer. This is a new FDA-approved technique that we uniquely provide at UCSF for patients with prostate cancer who need more information about their disease so they can make the most appropriate treatment decision and/or understand whether the therapy they’ve received is effective or not. Many of the men who we scan already have a proven cancer diagnosis, and we are trying to help them characterize the cancer – to learn if it is an aggressive cancer or an indolent cancer. The goal of the staging exam, in combination with ultrasound-guided biopsies, is to give the patient more information about his individual disease so he can select the best therapeutic approach.
By way of background, most of the imaging that we do with MRI – whether it be for prostate or other diseases – is anatomic imaging, where we look at the changes in anatomy or pathology with the presence and progression of the cancer. During the past 20 years of our work in prostate cancer we found that anatomic imaging had great sensitivity for picking up the disease, but it was not very specific because factors other than cancer – benign processes – led to changes in our images that looked like cancer.
Because we needed to get more information from our scan, we worked on adding a functional imaging parameter in the form of metabolism and identified several metabolic markers, which helped us discriminate cancer from other benign processes. The technique we developed was spectroscopic imaging, which allows us to look at metabolism in vivo. So we developed a combination of proton anatomic imaging and proton spectroscopic imaging and produced a commercially available staging exam with GE Healthcare. That was our first step in helping men better characterize their prostate cancer so they could select what to do next more appropriately.
In addition to metabolism, MRI now also allows us to look for additional pieces of information –parameters – that further characterize the cancer within the same exam; hence the name “multiparametric.” Another parameter that MRI allows us to look at is water diffusion, which gives us a picture of the cellularity of the tissue. We know that cellularity increases in cancer, and it changes after therapy as well. The other MRI parameter that we are looking at is the perfusion of the tissue. In cancer there must be an increased blood supply to deliver all the nutrients and oxygen required for the tumor to grow. We can measure the increase in that vasculature or perfusion of the tumor relative to the tissue. Both of these MRI parameters can be used not only for cancer detection, but also to characterize the cancer.
Furthermore, once our tests help us decide whether this is a man who needs to be treated aggressively for prostate cancer, our multiparametric imaging exam can be used to determine which of the multiple therapies currently available is best for the individual man we’re treating.
For more information on prostate cancer screening at UCSF, please see here.