Michael Chuong, MD, a board-certified radiation oncologist, is the medical director of the Proton Therapy Center, the physician director of the MRI-Guided Radiation Therapy Program, and the director of Radiation Oncology Clinical Research at Miami Cancer Institute, part of Baptist Health South Florida. He is an internationally recognized expert in the use of MRI-guided radiation therapy for gastrointestinal cancers. Dr. Chuong serves on several national committees including the NRG Oncology GI committee and is the Disease Site Chair for the Proton Collaborative Group.

Michael Chuong, MD

Michael D. Chuong, MD, a radiation oncologist and medical director of Proton Therapy at Miami Cancer Institute, Baptist Health South Florida, discusses the benefits of MRI-guided radiation therapy in pancreatic cancer.

is an ablative therapy typically administered over the course of 5 days. It is an option for patients who cannot undergo surgery, at least initially, and still have visible tumor in the pancreas itself. The method has proven more effective compared to lower doses of radiation, or even higher-dose regimens performed on different machines. According to Chuong, the machines seem to not only have an impact on tumor control, but also on long-term patient survival. 

A recent analysis found that patients who received MRI-guided ablative radiation therapy had a median survival of nearly 2 years after some chemotherapy, significantly longer than the historical average of a little over 1 year with standard dose radiotherapy. Additionally, these results were achieved with little significant adverse events. A number of patients reported no adverse events at all. According to Chuong, more studies are needed to confirm findings. 

 MRI-guided radiation therapy, which is typically delivered in 5 days here, although to an ablative dose, ablative means extremely high and having a surgical type of potential, is something that really could benefit any patient who has no option for surgery at least initially, and who has visible tumor in the pancreas itself. And this is something that we've seen have tremendous impact in terms of what seems to be improving long term local control, as opposed to lower doses of radiation, and even those that can be delivered in 5 days on a different machine. We're seeing potentially dramatic improvement in longevity of the ability to keep tumors from essentially regrowing or coming back in the treated area within the pancreas using ablative MRI guided radiation therapy. And what's exciting is that this seems to potentially not only have an impact on local tumor control, but also potentially a long-term patient survival.

 So, in our recent analysis, we demonstrated that patients who received ablative MRI guided radiation therapy here, after typically some amount of chemotherapy, had a median survival of nearly 2 years, which is significantly higher than the historical expected outcomes from standard dose radiation, which is typically about 1 year, maybe a little bit more than 1 year. And what's also exciting is that we achieved these results with most patients having no significant adverse effects or side effects. And in fact, a number of our patients really had no reported side effects at all, which is obviously tremendous. This is definitely an exciting time for pancreatic cancer patients as novel treatments such as ablative MRI-guided radiation is emerging. we clearly need additional studies to better understand what the long-term outcomes and results are from this type of treatment. But our experience here at Miami Cancer Institute is one of a growing number of studies that are emerging, essentially demonstrating very similar results leading to in leading to enthusiasm that in fact, this is a viable and promising approach moving forward for patients where surgery is not an option.

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Benefits of MRI-Directed Ablative Radiotherapy in Pancreatic Cancer

Pancreatic cancer is responsible for more than 48,000 deaths annually in the United States, making it one of the leading causes of cancer mortality.

Most pancreatic cancer patients have a short life expectancy because a diagnosis is not usually made until the cancer has progressed to an advanced stage, when symptoms such as jaundice and abdominal pain are more likely. As a result, complete surgical removal of the tumor is not possible for most patients. Chemotherapy and radiation therapy are typically recommended to slow tumor growth, but ultimately are not expected to be curative.

Over the last decade, the transition from single-agent to multi-agent chemotherapy has achieved a modest improvement in survival for unresectable pancreatic cancer. However, the approach to radiation therapy has not changed significantly over that same time, and the prescribed radiation dose has stayed within a modest range to prioritize patient safety. Recent studies have suggested that delivering much higher doses of radiation could potentially improve both local tumor control and potentially overall survival.

 However, the proximity of the stomach and intestines to the pancreas is a limiting factor in significantly escalating the radiation dose for most patients while not causing significant toxicity.

MRI-guided radiation therapy (abbreviated as MRgRT) is a novel treatment approach that is changing the paradigm for how certain tumors, including those of the pancreas, are fundamentally treated.

 Offered only at a limited number of centers worldwide, MRgRT utilizes pre-treatment MRI instead of the more typical CT scans to ensure accurate patient positioning, and uniquely can continuously image the patient’s internal anatomy throughout treatment delivery, allowing for any change to be detected in real time and automatically pausing treatment if the tumor shifts even a few millimeters out of the intended position. Another distinction of MRgRT is the ability to adapt the treatment plan each day based on changes in the patient’s internal anatomy, which ensures accurate tumor targeting and avoidance of nearby critical organs.

As the second institution in the United States to treat cancer patients with the ViewRay MRIdian Linac in 2018, Miami Cancer Institute, part of Baptist Health South Florida, has since become recognized as a global leader for MRgRT, with patients regularly seeking treatment there from across the country and internationally. The MRIdian Linac is routinely used at the Institute to treat the most challenging tumors with a higher dose than could be safely delivered on a standard radiation delivery machine. Treatment on the MRIdian Linac for many tumors can be completed in five or fewer days, is completely noninvasive, and does not require anesthesia, resulting in little to no downtime for patients.

At the European Society for Radiotherapy and Oncology annual conference in Madrid on August 29, I presented long-term outcomes of 50 inoperable pancreatic cancer patients treated with chemotherapy followed by stereotactic ablative body radiation therapy (SABR) on the MRIdian Linac. An ablative prescription dose was used (50 Gy in five fractions) and most patients were treated to elective regions in addition to gross disease. Nearly all fractions required that the treatment plan be adapted before treatment delivery because of interfraction anatomic changes in the stomach and/or small bowel position that would otherwise have resulted in dangerously high dose to these organs using the original plan.

While the historical median survival time for inoperable pancreatic cancer patients is only about 12-15 months after non-ablative radiation therapy, I reported that patients treated on the MRIdian Linac achieved a median survival of 21 months. In addition, while lower radiation dose is associated with 2-year survival of 20%, I reported 2-year survival of 50% with some patients being alive more than 3 years after their initial cancer diagnosis. Significant side effects were rare.

These exciting results support MRgRT as a potential paradigm shift in the management of inoperable pancreatic cancer, offering the possibility of achieving long-term survival while maintaining a high quality of life. I and my fellow investigators at Miami Cancer Institute are leading several novel clinical trials for pancreatic cancer and other challenging cancers using the MRIdian Linac that aim to significantly improve patient outcomes and redefine the standard of care for radiation therapy.

1. Siegel RL, Miller KD, Fuchs HE, et al. Cancer statistics, 2021. 

2. Hammel P, Huguet F, van Laethem JL, et al. Effect of chemoradiotherapy vs chemotherapy on survival in patients with locally advanced pancreatic cancer controlled after 4 months of gemcitabine with or without erlotinib: The lap07 randomized clinical trial. 

3. Krishnan S, Chadha AS, Suh Y, et al. Focal radiation therapy dose escalation improves overall survival in locally advanced pancreatic cancer patients receiving induction chemotherapy and consolidative chemoradiation. 

4. Rudra S, Jiang N, Rosenberg SA, et al. Using adaptive magnetic resonance image-guided radiation therapy for treatment of inoperable pancreatic cancer. 

5. Reyngold M, Parikh P, Crane CH. Ablative radiation therapy for locally advanced pancreatic cancer: Techniques and results. 

6. Hall WA, Paulson ES, van der Heide UA, et al. The transformation of radiation oncology using real-time magnetic resonance guidance: A review. 

Articles

Complete surgical removal of a pancreatic tumor is not possible for most patients. Chemotherapy and radiation therapy are typically recommended to slow tumor growth, but ultimately are not expected to be curative, writes Michael Chuong, MD. 

Michael Chuong, MD | Authors

Articles

Benefits of MRI-Directed Ablative Radiotherapy in Pancreatic Cancer

MRI-Guided Radiation Therapy: A Novel Treatment for Pancreatic Cancer