According to the Prostate Cancer Foundation, more than 60,000 American men opt for radiation annually.1 One of the key concerns with prostate radiotherapy, however, is limiting toxicity to important surrounding organs and other structures, including the bladder, rectum and heads of the femur, as well as normal tissue. But technology and technique advances in radiotherapy are allowing radiation oncologists to more precisely sculpt the radiation dose to maximize impact to the tumor while protecting surrounding tissue.
Brachytherapy delivers therapeutic dose directly to the tumor via an implanted radiation source that is either permanently or temporarily inserted in the region of interest. Permanent brachytherapy is also known as high dose rate (HDR) brachytherapy because it delivers a larger dose of radiation over a shorter period of time compared to temporary or low dose rate (LDR) brachytherapy.
Emory University Study
A group of researchers led by Deborah W. Bruner, RN, Ph.D., FANN, who is the senior vice president for research at Emory University, used a cohort of nearly 600 patients to evaluate the differences between progression-free survival and patient-reported outcomes (PROs) for toxicity for brachytherapy alone versus brachytherapy plus EBRT. “The patient-reported data confirms that brachytherapy alone is the superior treatment for this for men with intermediate-risk prostate cancer, with less patient-reported side effects. Brachytherapy alone would also be the most cost-efficient treatment option for patients,” stated Bruner.
Penn Medicine Study
A separate study from Penn Medicine at the University of Pennsylvania explored the possibilities of combining proton therapy, an advanced radiotherapy technique that has been growing rapidly in recent years, with hypofractionation to safely maximize dose to the tumor. In hypofractionation, the prescribed radiation dose is delivered in larger portions (fractions) over fewer treatment sessions than in traditional radiotherapy.
The Penn Medicine study looked at data on 184 men who received hypofractionated proton therapy for localized prostate cancer. Approximately four years post-treatment, 96 percent of the study cohort were still alive, and the four-year rate of serious gastrointestinal problems was 13.6 percent; the researchers noted that most of those problems occurred within the first two years after treatment. Of the patients who had GI effects, 79 percent experienced rectal bleeding. The cumulative four-year rate of urologic issue was 7.6 percent. The most common issue was needing to urinate frequently. However, all issues resolved within six months.
“This study provides some prospective evidence that the higher daily radiation dose delivered in hypofractionated proton therapy does not negatively impact patient quality of life,” said senior author Neha Vapiwala, M.D., an associate professor of radiation oncology. “This data can help guide clinicians and patients as they weigh treatment efficacy, tolerability and convenience.”
Intensity modulated radiation therapy (IMRT) has risen to become the gold standard for external beam radiation therapy in prostate cancer. The technique allows the radiation beams to be conformed more precisely to the target volume, and the intensity of each individual beam can be modulated for more precise dose sculpting.
ViewRay, which received U.S. Food and Drug Administration (FDA) clearance for the first MRgRT system in 2012, announced the findings of a 101-patient study at Amsterdam University Medical Center using MRIdian with intermediate- and high-risk prostate cancer patients, assessing GI and GU toxicity effects. At three months, no early grade 3 GU or GI toxicity — according to CTCAE (Common Terminology Criteria for Adverse Events) v4.0, a National Cancer Institute method for evaluating the effects of cancer therapy drugs — was observed. More impressively, the maximum cumulative grade 2 early GU and GI toxicity measured by any symptom at any study time point was 23.8 percent (study hypothesis 40 percent) and 5 percent (study hypothesis 15 percent).
“SBRT [stereotactic body radiation therapy] 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.”
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