First Toxicity Results from SCIMITAR Prospective Phase II Trial Signal Favorable Toxicity Profile of Post-Prostatectomy Stereotactic Body Radiotherapy (SBRT) for Prostate Cancer
Surgery, known as prostatectomy, is a common treatment for prostate cancer and it is estimated that up to 1/3 of patients will experience some recurrence of their cancer within 10 years after their prostatectomy. The current standard treatment for most patients with recurrent prostate cancer after surgery is up to 7-8 weeks of radiation therapy.
The first toxicity results from the trial, which will be presented at ACRO 2022, evaluated 100 patients with recurrent prostate cancer after radical prostatectomy. The patients underwent SBRT delivered under either CT guidance or MRI guidance. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicity were evaluated based on the Common Terminology Criteria for Adverse Events (CTCAE version 4.03). Patient-reported toxicity outcomes (PRO) were based on Expanded Prostate Cancer Index-26 (EPIC-26) instrument and International Prostate Symptom Scores (IPSS).
SBRT after prostatectomy was feasible, with a favorable overall toxicity profile both in clinician-scored and patient-reported outcome measurements. However, the post-hoc analysis signaled that MRI-guided radiation therapy may be associated with reduced acute physician-scored GI toxicity.
"When treating patients after a radical prostatectomy, the radiation target volume is a broader area between the rectum and the bladder. Because the rectum and the bladder can change shape and move, both between treatments and during treatments, we have had to use fairly generous "safety margins" when designing our radiation. That means we need to provide a dose to an area broader than just the target volume to ensure that we don't miss. For instance, on a recent nationwide trial, these margins ranged from 7 mm to 1 cm," said
The SCIMITAR trial will assess 4-year biochemical recurrence-free survival and analysis of the primary endpoint is planned once the 100th patient has 2-year PRO data available.
Additionally, another Phase II trial called SHORTER (NCT044221320) is underway at NewYork-Presbyterian/Weill Cornell Medicine, comparing in a randomized manner urinary and bowel side effects of MRI-guided hypofractionated radiotherapy in 20 treatments (4 weeks) to MRI-guided ultra- hypofractionated radiotherapy in 5 treatments (2 weeks) for prostate cancer that has returned after prostatectomy.
The MRIdian system provides oncologists outstanding anatomical visualization through diagnostic-quality MR images and the ability to adapt a radiation therapy plan to the targeted cancer with the patient on the table. This combination allows physicians to define tight treatment margins to avoid unnecessary radiation exposure of vulnerable organs-at-risk and healthy tissue and allows the delivery of ablative radiation doses in five or fewer treatment sessions, without relying on implanted markers. By providing real-time continuous tracking of the target and organs-at-risk, MRIdian enables automatic gating of the radiation beam if the target moves outside the user-defined margins. This allows for delivery of the prescribed dose to the target, while sparing surrounding healthy tissue and critical structures, which results in minimizing toxicities typically associated with conventional radiation therapy.
Nearly 18,000 patients have been treated with MRIdian. Currently, 50 MRIdian systems are installed at hospitals around the world where they are used to treat a wide variety of solid tumors and are the focus of numerous ongoing research efforts. MRIdian has been the subject of hundreds of peer-reviewed publications, scientific meeting abstracts, and presentations. For a list of treatment centers, please visit: https://viewray.com/find-mridian-mri-guided-radiation-therapy/
The opinions and clinical experiences discussed herein are specific to the featured physicians and are for information purposes only. Nothing in this material is intended to provide specific medical advice or to take the place of written law or regulations. Results of treatment presented in this press release are not indicative of typical or future results.
The MRIdian Linac System is not appropriate for all patients, including those who are not candidates for magnetic resonance imaging. Radiation treatments may cause side effects that can vary depending on the part of the body being treated. The most frequent ones are typically temporary and may include, but are not limited to, irritation to the respiratory, digestive, urinary or reproductive systems; fatigue; nausea; skin irritation; and hair loss. In some patients, side effects can be severe. Treatment sessions may vary in complexity and duration. Radiation treatment is not appropriate for all cancers. You should discuss the potential for side effects and their severity as well as the benefits of radiation and magnetic resonance imaging with your doctor to make sure radiation treatment is right for you.
Conflicts of Interest:
This press release contains forward-looking statements within the meaning of Section 27A of the Private Securities Litigation Reform Act. Statements in this press release that are not purely historical are forward-looking statements. Such forward-looking statements include, among other things,
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