On August 19, 2019 ViewRay, Inc. (Nasdaq: VRAY) reported the acceptance of publication by the International Journal of Radiation Oncology, Biology and Physics of the first prospective clinical trial of MR-guided radiation therapy (MRgRT) in patients with localized prostate cancer (Press release, ViewRay, AUG 19, 2019, View Source [SID1234538868]). This robust study of clinician and patient reported outcomes demonstrated zero CTCAE v4 grade 3 or higher gastrointestinal (GI) and genitourinary (GU) toxicity and even lower incidence of grade 2 toxicity than investigators hypothesized. It is also one of the first prospective clinical trials to study SBRT in a mix of intermediate- and high-risk prostate cancer patients, a challenging patient population to treat. The journal is the official scientific journal of the American Society for Radiation Oncology.
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Researchers from Amsterdam University Medical Center enrolled 101 patients with intermediate- or high-risk prostate cancer in a prospective phase II clinical trial. All patients received MRgRT in five fractions of 7.25 Gy to the target volume using on-table adaptive techniques. The trial did not use implanted markers or tissue spacers because treatments were delivered under MR-guidance, thereby eliminating an invasive procedure, potentially associated complications, and implantation costs.
Results at three months showed that no early CTCAE v4.0 grade 3 GU or GI toxicity was observed, and the maximum cumulative grade 2 early GU and GI toxicity measured by any symptom at any study time point was 23.8% (study hypothesis 40%) and 5.0% (study hypothesis 15%). These results were obtained in a complex clinical cohort (59.4% high-risk patients) and are comparable to what would be typically observed in lower-risk populations, pointing to the potential benefits of MR-guided SBRT in this higher risk group. Additionally, the low incidence of early GI toxicity, despite the inclusion of the base of the seminal vesicles in 96 percent of patients, illustrates the benefit of MR-guidance and on-table adaptive re-planning. This technology facilitates smaller treatment margins while minimizing damage to surrounding tissue and critical structures, such as urethra, rectum, and bladder. The publication noted that incontinence was uncommon, reported by 4% of patients at the end of MRgRT and decreasing over time.
"SBRT offers significant promise in the treatment of prostate cancer. Our clinical trial takes that a step further in showcasing its value in patients with intermediate- and high-risk disease, with a focus on evaluating associated toxicities and quality of life outcomes," said principal investigator Anna Bruynzeel, M.D., Ph.D., Radiation Oncologist at Amsterdam UMC. "We see a lower incidence of GI and GU toxicity with MR-guidance as compared to similar SBRT prostate cancer studies. The results reinforce the value of MRIdian’s real-time on-table adaptive treatment with automatic beam gating for prostate patients."
"This promising data in the treatment of prostate cancer with SBRT, enabled by the unique combination of MRIdian’s ability to see, shape, and strike, is notable for patients and physicians," said Scott Drake, President and CEO. "MRIdian is providing physicians the confidence and tools they need to deliver ablative radiation doses both precisely and accurately while sparing sensitive structures near the target, in order to achieve better patient outcomes. We are pleased to add this prospective trial to our clinical data compendium and thank the team at Amsterdam UMC for their work to improve the lives of cancer patients."
The article in press can be viewed at View Source(19)33640-5/fulltext.
About the Study
Article in Press in the International Journal of Radiation Oncology, titled: "A prospective single-arm phase II study of stereotactic magnetic-resonance-guided adaptive radiotherapy for prostate cancer: Early toxicity results", authored by Anna M.E. Bruynzeel, MD, PhD, Shyama U. Tetar, MD, Swie S. Oei, MD, Suresh Senan, MRCP, FRCR, PhD, Cornelis J.A. Haasbeek, MD, PhD, Femke O.B. Spoelstra, MD, PhD, Anna H.M. Piet, MD, Philip Meijnen, MD, PhD, Marjolein A.B. Bakker van der Jagt, MD, Tamara Fraikin, Berend J. Slotman, MD, PhD, Reindert J.A. van Moorselaar, MD PhD, and Frank J. Lagerwaard, MD, PhD. According to the study, "The maximum cumulative grade ≥2 early GU and GI toxicity measured by any symptom at any study time point was 23.8% and 5.0%, respectively. No early grade 3 GI toxicity was observed. Early grade 3 GU toxicity was 0% and 5.9% according to the CTCAE and RTOG and scoring systems, respectively, as a result of different grading of radiation-cystitis. The low incidence of early GI toxicity was confirmed by patient-reported outcome data. GU grade ≥2 toxicity peaked to 19.8% at the end of MRgRT, followed by a return to the baseline average score at three months follow-up."