The first trial of safety and toxicity shows promise for stereotactic radiosurgery as a therapeutic option for patients with localized primary renal cancer who are considered poor surgical candidates and who do not have a prior history of pelvic or abdominal radiation, according to research presented today at the American Society for Radiation Oncology’s 54th Annual Meeting (ASTRO) held in Boston, October 28 – 31, 2012, is the premier scientific meeting in radiation oncology.
This study of stereotactic radiosurgery, a form of radiation therapy that focuses high-powered x-rays on a small area of the body rather than affect nearby healthy tissue, presents results of patients from two to 41 months post-treatment using a four-part dose escalation schema. The response rate indicates that patients reacted well and had acceptable levels of treatment-related toxicity following stereotactic radiosurgery in all age groups from 58 to 92 years old. There were no reports of gastrointestinal or small bowel toxicity, or cancer-related deaths. For 94% of patients across all four groups, their tumors remained stable or decreased on post-treatment imaging. For patients who underwent a post-treatment biopsy, incomplete or refractory treatment was found in 91%, which suggests the need for higher radiation doses for adequate tumor control. Acute toxicity was limited to Grade 1 fatigue in two patients in the highest dose treatment group, which was relieved by rest. Late toxicity was limited to worsening of preexisting chronic renal disease in two patients who had a mean epidermal growth factor receptor (EGFR) of 19.5.
Non-prohibitive levels of toxicity
Twenty patients ranging from 58 to 92 years old received initial doses of 600 cGy per fraction, followed by increments of 200 cGy per fraction to total doses of 24 Gy, 32 Gy and 48 Gy. Doses were escalated after patients showed non-prohibitive levels of toxicity within 180 days from the date of treatment. Limiting levels of toxicity were defined as any Grade 3 or higher gastrointestinal/genitourinary acute radiation toxicity, according to the National Cancer Institute common toxicity criteria. Imaging and post-treatment biopsy results were evaluated for tumor response and treatment efficacy.
“Our first trial shows that low to moderate doses of stereotactic radiosurgery is a safe and viable option for renal cancer patients who typically do not have surgical options,” said Rodney J. Ellis, MD, lead author of the study, clinical director and vice chair for clinical affairs of the department of radiation oncology at University Hospitals Case Medical Center Seidman Cancer Center, and an associate professor in radiation oncology and urology at Case Western Reserve University School of Medicine in Cleveland. “Lee Ponsky, who is the principle investigator for this study from the department of urology, and I agree that further studies are needed to determine safe levels for the maximum dosage. By doing so, we hope to find increased response and cure rates with this method.”
The abstract, “Stereotactic Radiosurgery for Renal Cancer: Phase I Safety and Toxicity,” was be presented during a scientific session at ASTRO’s 54th Annual Meeting at 11:00 a.m. Eastern time, on Wednesday, October 31, 2012.
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