Posted on Oct 28, 2021
With greater sensitivity than traditional imaging techniques, PSMA (prostate-specific membrane antigen) is helping doctors catch prostate cancer spread that was previously difficult to detect and localize. We spoke with Dr. Jaideep Sohi, a Johns Hopkins fellowship-trained nuclear medicine specialist and Radiologist at DocPanel, to learn more about his experience working with PSMA in the clinical trial phase. Here, he shares how PSMA is transforming patient care and offers guidence on how imaging centers can integrate the new tracer into their service offerings.
[DocPanel] What is the significance of having new tracers? What are the benefits?
Developing new PET tracers allows us to better image, and therefore better understand, disease processes. This enables us to optimize treatment planning and improve overall patient outcomes. For example, in 2012 new Amyloid tracers were approved for PET imaging of the brain. These tracers are now starting to be used routinely (mainly via the ACR-sponsored IDEAS study) to help in the management of patients with mild cognitive impairment. We also have Netspot and Detectnet, which were developed over the last few years to image patients with well-differentiated neuroendocrine tumors. Cerianna is another new tracer; it’s used in PET imaging for patients who have estrogen receptor-positive breast carcinoma to help guide treatment. Most recently, we have PSMA, which was recently approved and is indicated for patients who have prostate cancer with suspected metastasis who are being evaluated for initial definitive therapy and with those who have previously been treated for prostate cancer and are now coming back with suspected biochemical recurrence based on elevated prostate-specific antigen (PSA) levels.
[DocPanel] Much of your recent work has focused on PSMA, which is quite exciting since, as you mentioned, it was just approved by the FDA. Can you expand a bit on how this tracer works and how it’s transforming care for patients with prostate cancer?
PSMA stands for prostate-specific membrane antigen. In a PSMA targeted PET-CT, the tracer used for the PET scan includes a molecule that specifically binds to PSMA, which is often found in large amounts on prostate cancer cells. This allows us to evaluate patients with prostate cancer metastases with much greater accuracy than ever before.
Prior to PSMA, our imaging options included MRI, CT, and bone scan, etc. These all have value, but they also have limitations that create major challenges in managing patients with prostate cancer. Prostate MRI, for example, is great for looking at the prostate - but it only looks at that general area, not the whole body. A bone scan, on the other hand, does look at the whole body - but it’s not very sensitive. If the patient doesn't have very markedly increased PSMA, a bone scan will often under call or not pick up bony metastatic disease.
The same goes for CT. Generally, patients are staged and restaged with CT of the abdomen and pelvis. What tends to happen though - especially in patients with known prostate cancer and concern for recurrence - is that unless lymph nodes seen on the CT are enlarged (usually more than 1 centimeter in short axis dimension), we do not call them abnormal based on size criteria. This is a huge cause for concern because up to two-thirds of patients with recurrent prostate cancer have nodes that are not enlarged according to CT criteria. It’s difficult to provide patients with good, actionable information when the tools being used have this sort of limitation.
With PSMA, we now have a modality that can look at the whole body. It can evaluate the prostate and the prostate bed, check for small lymph nodes in the abdomen and pelvis, look at other organs such as lungs, and assess the bones for any presence of metastatic disease. It brings the best of all modalities into one, but with greater accuracy. As I mentioned, there are 2 main indications for PSMA PET/CT. The first is patients with newly diagnosed prostate cancer where there’s a concern for metastatic disease in the body. PSMA helps plan treatment for these patients. The second is patients who have had prior treatment, for example, a prostatectomy or radiation therapy, and are now coming back with what we call biochemical recurrence. In this case, a patient’s PSA values have gone back up, indicating a new tumor. PSMA enables us to determine the site where cancer is coming back. For these two sets of patients, PSMA makes a huge difference.
[DocPanel] Can you share a bit about your role in clinical trials? What does this phase of development look like and how does it translate into ensuring expertise and specialization within a new modality?
Before new products like PSMA are brought into use, they go through an intense review phase and are evaluated in a clinical trial setting. This allows us to make sure that they are safe for patients and that they are going to make a positive impact on patient care. My team and I are heavily involved with the clinical trial phase.
Once we have substantial confidence that a tracer is ready for use in our communities, we become a resource for imaging centers to provide support. It’s important to remember, that when a new tracer comes out - those who have worked in the clinical setting have had an opportunity to develop expertise. That expertise can, of course, be shared but it’s crucial that providers understand the need for proper training. My team and I help facilities optimize imaging protocols, we provide training workshops for technologists, and we help train radiologists how to read to studies with the new imaging agent(s). Another crucial component is the education we offer referring providers regarding what tracer to use, when to use it, and how to interpret the information provided on reports. Ultimately, everything we are doing is to help patients. We practice and value a team approach.
[DocPanel] How can providers navigate adding PSMA into their service offerings? What are the steps they need to take? What are the biggest challenges imaging facilities face when integrating new tracers into their PET protocols?
Since PSMA has only recently been approved by the FDA, imaging providers will need to consider several factors - cost, availability, and expertise. In terms of cost, it may take some time for insurance providers to start covering PSMA. As far as availability, only two entities are producing PSMA agents right now so demand may exceed supply. But several other radiopharmaceutical companies are also working on producing their own version, so there will be more PSMA products on the market soon.
The third, and equally important consideration involved with offering a new tracer is ensuring you have personnel with adequate expertise to execute the new modality. Technologists will need to be trained on how to perform the exam and radiologists will need to know how to read the scans. A certain level of technical training and resources will be offered by the company supplying the tracer; however, the depth can vary from company to company.
One of the biggest issues in the market now, however, is that given how new the PSMA tracer is, very few nuclear medicine specialists and radiologists are experienced with interpreting these exams. Fortunately, there is a solution. Through DocPanel, imaging centers can access a team of physicians who are highly trained in PSMA (or any other type of modality, for that matter). The team, whom I will be leading, have all developed expert knowledge on the modality through various endeavors, such as clinical trials and peer-to-peer reviews. We would also work closely with the imaging center personnel to obtain access to the novel PET tracers via the vendors. The idea here is to eliminate as many of the obstacles encountered with incorporating the new tracer as possible. Through DocPanel, providers can get coverage for primary reads, help with setting up protocols, and educational consults for challenging cases. Working closely with the PSMA vendors, imaging center staff, and payors, our goal is to bring PSMA to as many patients as we can.
Interested in working with Dr. Sohi to incorporate PSMA into your service offerings? Send us a note here and we’ll set up a time to chat.