(ChemotherapyAdvisor) – The first prospective study of stereotactic radiosurgery for the treatment of patients with localized primary renal cancer has found it to be well tolerated, investigators concluded during the American Society for Radiation Oncology’s (ASTRO’s) 54th Annual Meeting, Boston, MA.

“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 lead author Rodney J. Ellis, MD, University Hospitals Case Medical Center Seidman Cancer Center, and Case Western Reserve University School of Medicine, Cleveland.

Patient outcomes from 2 to 41 months after treatment with stereotactic radiosurgery using a four-part dose escalation schema were presented. An initial dose of 600 cGy per fraction was delivered, followed by dose escalation of 200 cGy increments per fraction to total doses of 24 Gy, 32 Gy, and 48 Gy maximum dose.

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Twenty patients, 15 men and 5 women, ages 58-92 years (mean age, 80 years) without history of prior pelvic or abdominal radiation were assigned to treatment groups according to the dose escalation schema (4 to 24 Gy, 6 to 32 Gy, 4 to 40 Gy, and 6 to 48 Gy).

“We found acceptable levels of treatment related toxicity following stereotactic radiosurgery,” Dr. Ellis said. “Acute toxicity was limited to Grade 1 fatigue (relieved by rest) in 2 patients, both in the 48 Gy treatment group. Late toxicity was limited to worsening of preexisting chronic renal disease (an expected consequence of treatment in the 2 patients having a mean eGFR of 19.5), 1 each in the 24 Gy and 40 Gy treatment groups.”

No gastrointestinal or small bowel toxicity or cancer-related deaths were reported. Tumor response rate, defined by stable or reduced tumor volume on posttreatment imaging, was observed in 94% of patients across all treatment groups. For the subset having undergone a posttreatment biopsy, incomplete or refractory treatment was found in 91%, suggesting the need for higher radiation doses for adequate tumor control.

“We recommend initiation of a follow-on stereotactic radiosurgery trial for renal cancer, utilizing a 3-part dose-escalation schema defined as 3 fractions in 200 cGy increments to 48 Gy, 54 Gy, and 60 Gy maximum total dose,” he said. “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.”

Abstract (Search for Abstract 294)