Peter L. Choyke, MD, FACP, discusses the clinical implications of emerging technologies for prostate cancer imaging.
Peter L. Choyke, MD, FACP
Multimodality imaging holds the keys to providing personalized therapy to patients with prostate cancer, said Peter L. Choyke, MD, FACP.
Each screening platform has pros and cons, but their limitations can be erased with a combined effort, added Choyke, who is director of the Molecular Imaging Program and head of the Imaging Section at the National Cancer Institute (NCI).
For example, an MRI gives a standard anatomical overview of a tumor but is not specific enough, he said. A PET scan offers more specificity but lacks in terms of anatomy. In combination, however, these 2 options have a greater benefit.
“It is really about getting a more complete picture about where a patient stands in their disease’s natural history,” Choyke said.
Additional imaging methods have helped evolve this area in prostate cancer, including MRI ultrasound fusion-targeted biopsy and PSMA-PET.
In an interview with OncLive®, Choyke discussed the clinical implications of emerging technologies for prostate cancer imaging.Choyke: Our team at the NCI developed a method of fusing MR images with ultrasound images so that we could do fusion biopsies of prostate cancer. It has really taken off. There are now a lot of people doing it, and we are really gratified by that. That is a fusion of MRI and ultrasound. We then moved on to looking at PET scans, particularly one that targets prostate-specific membrane antigen (PSMA), which is found in more aggressive cases of prostate cancer. It is very specific.
We are finding out a lot of new things about prostate cancer because this is a changing picture of the disease. We are combining some of the traditional PET imaging like 18F-sodium fluoride bone scans with PSMA. We are finding some interesting things there. It is combining different methods together to figure out what's going on and guide management of patients.There was this widespread idea that doctors were either just MRI specialists or they were PET specialists. Now, we view it as whatever the best tool is to handle that particular problem is the way to go. For example, I started out as an MRI specialist, but I quickly realized there were limitations to what an MRI can do. Particularly, an MRI lacks specificity. We could see lesions, but we could not see whether they were cancerous or not. PET offers specificity, but the anatomy is not that good. You get the anatomy from the MRI and the sensitivity from the PET, and those 2 things go together very nicely.
We want to more accurately say, "This is where you are now, and this is the best therapy." We want to match the right diagnosis with the right therapy.It is very important. One of the things we are finding is that the disease goes over multiple disciplines. You have to bring all kinds of different management strategies to the table at different points in the disease. Depending on what the imaging shows, you can bring in different specialists. It is very important to have everybody at the table because the old way is for a patient to see 1 specialist. If the imaging or clinical parameters point in a different direction, you would want an additional specialist. The way to address that is a multidisciplinary approach so everybody sees everything, and you can decide on the best direction. We have done this at the NCI.We are comparing 2 different kinds of PET scans. We are looking at PSMA scans and 18F-sodium fluoride PET scans, which is a type of bone scan. We are finding that they do not completely match up with each other. Early on in the disease, they match up better. However, as the disease progresses, you get progressively less matching up. This is important because some therapies are very dependent on the bone turnovers. This is reflected by sodium fluoride.
We are finding that PSMA-PET scans, which indicates where the active disease is, sometimes does not overlap with the sodium fluoride. You can administer an agent like radium-223 dichloride (Xofigo), but it will not treat the cancer. We are learning about how to get smarter with selecting patients for radium-223 to make sure the right patient gets the right therapy.
PSMA-PET scan can be linked to a therapeutic radioisotope. It is very exciting to be able to put a therapy on the PSMA, so it will go to the lesion and treat it using targeted radionuclides. It is already in Europe and has had some dramatic responses. Some were even complete responses. We are very eager to go in that direction at NCI, and we have some planned studies coming up.