Radiation oncologist at the City of Hope, Terrence Williams, MD, talks about treating late-stage cancers with a new procedure.
Interview conducted by Ivanhoe Broadcast News in 2023.
So we’re talking about treating me metastatic lung and bone cancer. So are those traditionally just very hard to treat cancer?
Williams: When we treat metastatic lung or bone disease, we’re usually talking about stage 4 cancer at that point. The recent clinical evidence suggests that if patients have oligo or a few metastasis from a lung cancer that spread throughout the body, local therapies such as radiation or needle ablation or surgery can be effective at prolonging survival in those patients. We’re starting to think about more and more utilizing modalities like radiation or stereotactic body radiation therapy to control oligo metastatic disease. And in some cases, oligo progressive disease, which is when the tumors grow through a current therapy like chemotherapy or immunotherapy.
Is there a difference? I don’t know the difference between radiotherapy and radiation.
Williams: We use the terms interchangeably.
With radiation, I think, historically, there’s always the risk of burning, basically, extra things that are not the cancer, right?
Williams: That’s correct, yes. You know, I think as a modality, we’ve become much better at targeting the tumors and the cancer and avoiding radiation dose to the normal organs. Let me call the organs at risk. That is done through advancements in imaging and physics calculation of radiation dose and targeting, devising the fields of radiation in the machine that rotates around the patient in which the fields are delivered.
Now, there’s a new form though of radiotherapy that’s going to help you be even more precise in that, correct?
Williams: We believe so. One therapeutic option that is emerging now is something called biology-guided radiation therapy.
Is that what RefleXion X1 is?
Williams: That’s correct. The RefleXion X1 linear accelerator is the world’s first real-time PET-guided linear accelerator. In other words, it uses positron emissions from the tumor to triangulate where the tumor is in the body. And then within a millisecond shot radiation beams back at the target. Real-time PET-guided radiation therapy is utilizing the positron emission that comes from the tumor to triangulate where the tumor is in the body and immediately target radiation back to the tumor. That’s in essence what the RefleXion X1 Linear Accelerator technology that we have at the City of Hope is all about.
You had mentioned that it does it at an incredible speed, right?
Williams: It does, it triangulates the position of the tumor using these positrons that are almost like a light source or beacon from the tumor to then shoot radiation right back at the tumor within a millisecond. And what that enables the equipment to do is be less concerned with the motion of the tumor. So in particular parts of the body such as the lung, the upper abdomen, or other locations, the tumor is moving due to normal physiologic breathing or other body movements. We have to count for that. Traditionally, with motion management strategies, whether it’s breath hold, we ask the patient to hold their breath, or we only turn the beam on when the tumor is in a particular position. But with this new technology, because it detects the tumor so quickly and shoots radiation right back at it, the need for motion management becomes much less, if nonexistent.
Do you think this is something that will be just used across the board then for every type of tumor?
Williams: Well, I think we have a lot to learn about the technology right now. So the current version of the technology, we use a radiotracer called fluorodoxic glucose, which is a standard radiotracer used for PET scans. That lights up tumors that are taking up a lot of glucose if you will, and during the process of growth and proliferation. Whether that’s the right radiotracer for every tumor remains to be seen. In fact, many tumors don’t take up enough glucose signal to make a bright enough signal that we can use technology to target radiation with. But there are a whole host of other radiotracers coming down the pike that specifically target prostate cancer or even potentially breast cancer, or even a pan tumor signal with a new radiotracer that actually lights up fibroblasts, cancer-associated fibroblasts. So we’ll have to test each radio tracer individually for its ability to identify the tumor within the body, and efficiently use it to target our radiation back at the tumor.
Now, were you part of the clinical trials with City of Hope?
Williams: Some of the initial studies utilizing technology? Yes, City of Hope has been involved in those initial studies.
Do you have any specific stats or anything that you found interesting from those?
Williams: In our initial studies, we found that the machine is quite effective at doing what it’s theoretically supposed to be doing, which is identify the tumors and successfully deliver radiation to them using the beam modeling and other aspects of the treatment.
Is there anyone with these type of lung and bone cancers that this wouldn’t be good for?
Williams: I think right now we’re still learning about the technology, but we’re restricting our current entry of patients to be treated at City of Hope to larger tumors. We want to see a tumor that’s at least a centimeter in size, but no more than five centimeters in a particular dimension. Whether or not there’s sufficient FDG signal. Because as we roll out this technology, we’re starting with the FDG radiotracer. So we want to see that the signal is bright enough for us to detect on the machine and effectively target.
Now, were you surprised at all when you first saw the difference in what you could see in the tumor? Can you explain the difference in it?
Williams: I think the machine has an onboard traditional imager which is a CT-based imager. We’ve been very impressed. The technology has a specific onboard CT imager. I would say the quality of that imager is quite good. Now, the actual PET-guided portion of the treatment, we haven’t actually started yet. We’re actually in the process of identifying our first patient, but through a number of different studies that we have done, we call the non-significant risk studies, we’ve been impressed with the imager so far.
What is the number one advantage of using this?
Williams: I think personalization of therapy, utilizing the tumors inherent biology to target radiation. And the potential for this technology to avoid the need to manage motion is another aspect of it. Then third is really as the machine develops new iterations, the hope is that at some point we’ll be able to treat much more comprehensively, all the disease that’s in the body through treatment of multiple different tumors. More than say, one or two, but maybe 3-5 or even beyond 5-10 tumors, all in one session.
END OF INTERVIEW
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