Skip to content
  • About
  • Contact
  • Contribute
  • Book
  • Careers
  • Podcast
  • Recommended
  • Speaking
  • All
  • Physician
  • Practice
  • Policy
  • Finance
  • Conditions
  • .edu
  • Patient
  • Meds
  • Tech
  • Social
  • Video
    • All
    • Physician
    • Practice
    • Policy
    • Finance
    • Conditions
    • .edu
    • Patient
    • Meds
    • Tech
    • Social
    • Video
    • About
    • Contact
    • Contribute
    • Book
    • Careers
    • Podcast
    • Recommended
    • Speaking

Breakthrough trial shows MRI-guided radiation can reduce prostate cancer treatment toxicity

Amar U. Kishan, MD
Conditions
April 29, 2023
Share
Tweet
Share

Nearly 290,000 American men will be diagnosed with prostate cancer in 2023. Thankfully, the vast majority will be diagnosed with clinically localized disease and can be cured with either surgery or radiotherapy. Emerging clinical trial data have cemented stereotactic body radiotherapy (SBRT), a form of radiation in which ≤5 daily doses are delivered with high precision in generally five or fewer treatments, as a curative option for most men with localized prostate cancer. Because cure rates are so high, post-treatment quality of life (QOL) is often the major concern for patients with a new diagnosis of prostate cancer.

With respect to radiotherapy of any kind, including SBRT, the major QOL impacts can be categorized into one of three domains: genitourinary (GU), gastrointestinal (GI), and sexual. These domains can be impacted because the prostate is in close proximity to the bladder, urethra, rectum, and neurovascular structures that are related to normal urinary, bowel, and sexual function. As a result, due to the physics of dose-delivery, even with perfect precision, there will be a range of radiation dose impacting these normal structures (called organs-at-risk).

This intrinsic dose fall-off is compounded by the fact that, when any form of external beam radiotherapy is delivered, the existence of several basic uncertainties in targeting lead to physicians treating not just the prostate, but a margin around the prostate. The major contributor to this margin is motion. In fact, the prostate moves not just between treatments, but actually during treatments as well. Careful estimates have calculated that in a 3-minute timeframe – the time required to deliver modern SBRT on most gantry-mounted linear accelerators — the margin around the prostate that would need to be targeted to encompass the majority of positions the prostate could be in is approximately 3 mm in the superior-inferior and anterior-posterior dimensions and about 2 millimeters in the right-left dimension. Due to additional considerations (like minor differences in patient positioning and delineation of the target), recommended margins are typically on the order of 5 millimeters in each dimension. This means that the area intentionally receiving the prescription dose of radiation would be not just the prostate, but a 5 mm sphere around the prostate. Given the significant negative QOL impact that bowel toxicity can have, margins as narrow as 3 mm in the posterior direction (i.e., behind the prostate) have been accepted as well. The University of California, Los Angeles (UCLA) has been a bastion of SBRT for well over a decade, and our team settled on a margin of 4 mm around the prostate for routine SBRT.

In 2019, MRI-guided linear accelerators (MR-LINACs), a novel form of radiotherapy technology, became more widely available commercially. MR-LINACs offer several theoretical advantages in the context of prostate SBRT, where high accuracy and precision are required.  First, MR-LINACs allow direct visualization of the prostate on the delivery platform. The resolution and contrast of standard CT images is suboptimal for visualization, which is why often metal fiducial markers are implanted into the prostate prior to radiotherapy. With MR-LINACs, these are not needed. Second, and perhaps most importantly, the MR-LINACs can monitor the position of the prostate with extremely high frequency (up to four times a second) and can automatically pause radiation delivery if the prostate moves out of a preset boundary. We acquired the MRIdian MR-LINAC from ViewRay, Inc. in late 2019, and it became readily apparent that we could confidently treat the prostate with much tighter margins than we had historically used, on the order of 2 mm.

But a question remained – would a reduction in these margins, from 4 mm (our standard with a CT-guided platform) to 2 mm (with the MR-LINAC) lead to improved outcomes for patients? It may seem self-evident that radiating a smaller volume of tissues will lead to lower toxicity, but the medical field is replete with “good ideas” that ultimately failed to achieve their potential. Thus, given our unique expertise in CT-guided SBRT, our experience with developing and running trials, and our commitment to demonstrating value, we launched the randomized MIRAGE trial (NCT04384770) to demonstrate whether the tightened margins afforded by the MR-LINAC reduced toxicity. Specifically, this trial, which ran from May 2020 to October 2021 and enrolled 156 patients, was designed to evaluate whether acute moderate grade or greater GU toxicity (i.e., grade ≥2) would be reduced as a result of the tighter margins.

The primary endpoint results of the trial, published in JAMA Oncology on January 12, 2023, found that this aggressive margin reduction did translate to reduced toxicity. Rates of grade ≥2 GU toxic effects were significantly lower with MRI vs. CT guidance (24.4% vs. 43.4%). Additionally, rates of grade ≥2 toxic effects were also significantly lower with MRI guidance vs. CT guidance (0.0% vs. 10.5%).  The percentage of patients who self-reported a substantial increase in urinary symptoms increase was significantly greater with CT guidance at 1 month (19.4% vs 6.8%), as was the percentage of patients who noticed clinically significant impairments in bowel symptoms (50.0% vs. 25.0%).

In summary, the MIRAGE trial primary analysis demonstrates that the use of MRI guidance in the context of prostate SBRT leads to reduced physician-scored and patient-reported urinary and bowel toxicity. This advantage is attributable to MRI guidance allowing enhanced physical precision, with a 2 mm PTV margin around the prostate being targeted rather than a standard-of-care 4 mm PTV margin. Based on the positive results of the MIRAGE trial, we have changed our practice to offering MRI-guided SBRT as our preferred institutional standard of care.

Perhaps the biggest takeaway from the trial is that as we enter the era of precision medicine in oncology, our definition of precision can and should extend beyond the biological precision that comes from a deeper understanding of cancer physiology. Indeed, the MIRAGE trial has shown us that the benefits of physical precision are not illusory, but tangible.

Amar U. Kishan is a radiation oncologist.

Prev

Generational differences in medical practice: Exploring work habits of Baby Boomers, Generation X, and Millennials

April 29, 2023 Kevin 0
…
Next

Lessons from a caregiver for a rare neurodegenerative disorder [PODCAST]

April 29, 2023 Kevin 0
…

Tagged as: Oncology/Hematology

Post navigation

< Previous Post
Generational differences in medical practice: Exploring work habits of Baby Boomers, Generation X, and Millennials
Next Post >
Lessons from a caregiver for a rare neurodegenerative disorder [PODCAST]

ADVERTISEMENT

Related Posts

  • Is social media a friend or foe of science?

    Michael Joyce, MD
  • Hormone replacement therapy is still linked to cancer

    Martha Rosenberg
  • A patient’s experience of chemotherapy and radiation

    Lynn Lazos
  • We have a shot at preventing cervical cancer

    Lisa N. Abaid, MD, MPH
  • Caught in the middle: How health insurance companies influence cancer drug selection

    Paul Pender, MD
  • Despite progress in cancer care, cost and equity challenges still must be addressed

    David M. Aboulafia, MD

More in Conditions

  • What Elon Musk and Diddy reveal about the price of power

    Osmund Agbo, MD
  • Understanding depression beyond biology: the power of therapy and meaning

    Maire Daugharty, MD
  • Why medicine must stop worshipping burnout and start valuing humanity

    Sarah White, APRN
  • Why perinatal mental health is the top cause of maternal death in the U.S.

    Sheila Noon
  • A world without vaccines: What history teaches us about public health

    Drew Remignanti, MD, MPH
  • Unraveling the mystery behind one of the most dangerous pregnancy complications: preeclampsia

    Thomas McElrath, MD, PhD and Kara Rood, MD
  • Most Popular

  • Past Week

    • Why are medical students turning away from primary care? [PODCAST]

      The Podcast by KevinMD | Podcast
    • Why “do no harm” might be harming modern medicine

      Sabooh S. Mubbashar, MD | Physician
    • How New Mexico became a malpractice lawsuit hotspot

      Patrick Hudson, MD | Physician
    • Why doctors are reclaiming control from burnout culture

      Maureen Gibbons, MD | Physician
    • Why helping people means more than getting an MD

      Vaishali Jha | Education
    • Why public health must be included in AI development

      Laura E. Scudiere, RN, MPH | Tech
  • Past 6 Months

    • Why tracking cognitive load could save doctors and patients

      Hiba Fatima Hamid | Education
    • Why are medical students turning away from primary care? [PODCAST]

      The Podcast by KevinMD | Podcast
    • What the world must learn from the life and death of Hind Rajab

      Saba Qaiser, RN | Conditions
    • Why “do no harm” might be harming modern medicine

      Sabooh S. Mubbashar, MD | Physician
    • Here’s what providers really need in a modern EHR

      Laura Kohlhagen, MD, MBA | Tech
    • Why flashy AI tools won’t fix health care without real infrastructure

      David Carmouche, MD | Tech
  • Recent Posts

    • Why helping people means more than getting an MD

      Vaishali Jha | Education
    • How digital tools are reshaping the doctor-patient relationship

      Vineet Vishwanath | Tech
    • Why evidence-based management may be an effective strategy for stronger health care leadership and equity

      Olumuyiwa Bamgbade, MD | Physician
    • Why health care leaders fail at execution—and how to fix it

      Dave Cummings, RN | Policy
    • Residency match tips: Building mentorship, research, and community

      Simran Kaur, MD and Eva Shelton, MD | Education
    • From Founding Fathers to modern battles: physician activism in a politicized era [PODCAST]

      The Podcast by KevinMD | Podcast

Subscribe to KevinMD and never miss a story!

Get free updates delivered free to your inbox.


Find jobs at
Careers by KevinMD.com

Search thousands of physician, PA, NP, and CRNA jobs now.

Learn more

Leave a Comment

Founded in 2004 by Kevin Pho, MD, KevinMD.com is the web’s leading platform where physicians, advanced practitioners, nurses, medical students, and patients share their insight and tell their stories.

Social

  • Like on Facebook
  • Follow on Twitter
  • Connect on Linkedin
  • Subscribe on Youtube
  • Instagram

ADVERTISEMENT

  • Most Popular

  • Past Week

    • Why are medical students turning away from primary care? [PODCAST]

      The Podcast by KevinMD | Podcast
    • Why “do no harm” might be harming modern medicine

      Sabooh S. Mubbashar, MD | Physician
    • How New Mexico became a malpractice lawsuit hotspot

      Patrick Hudson, MD | Physician
    • Why doctors are reclaiming control from burnout culture

      Maureen Gibbons, MD | Physician
    • Why helping people means more than getting an MD

      Vaishali Jha | Education
    • Why public health must be included in AI development

      Laura E. Scudiere, RN, MPH | Tech
  • Past 6 Months

    • Why tracking cognitive load could save doctors and patients

      Hiba Fatima Hamid | Education
    • Why are medical students turning away from primary care? [PODCAST]

      The Podcast by KevinMD | Podcast
    • What the world must learn from the life and death of Hind Rajab

      Saba Qaiser, RN | Conditions
    • Why “do no harm” might be harming modern medicine

      Sabooh S. Mubbashar, MD | Physician
    • Here’s what providers really need in a modern EHR

      Laura Kohlhagen, MD, MBA | Tech
    • Why flashy AI tools won’t fix health care without real infrastructure

      David Carmouche, MD | Tech
  • Recent Posts

    • Why helping people means more than getting an MD

      Vaishali Jha | Education
    • How digital tools are reshaping the doctor-patient relationship

      Vineet Vishwanath | Tech
    • Why evidence-based management may be an effective strategy for stronger health care leadership and equity

      Olumuyiwa Bamgbade, MD | Physician
    • Why health care leaders fail at execution—and how to fix it

      Dave Cummings, RN | Policy
    • Residency match tips: Building mentorship, research, and community

      Simran Kaur, MD and Eva Shelton, MD | Education
    • From Founding Fathers to modern battles: physician activism in a politicized era [PODCAST]

      The Podcast by KevinMD | Podcast

MedPage Today Professional

An Everyday Health Property Medpage Today
  • Terms of Use | Disclaimer
  • Privacy Policy
  • DMCA Policy
All Content © KevinMD, LLC
Site by Outthink Group

Leave a Comment

Comments are moderated before they are published. Please read the comment policy.

Loading Comments...