BOSTON—Researchers have reported promising results from the first safety trial of stereotactic radiosurgery for patients with localized primary renal cell carcinoma (RCC) who are considered poor surgical candidates and who do not have a prior history of pelvic or abdominal radiation, according to a new study.

“This is a huge first step to show this is safe,” said lead investigator Rodney Ellis, MD, Clinical Director and Vice Chair for Clinical Affairs in the Department of Radiation Oncology at University Hospitals Case Medical Center Seidman Cancer Center in Cleveland. “We are very pleased with the findings, and I think this is good news for urologists and their patients because it may give them another option that is non-invasive.” Dr. Ellis also is an associate professor of radiation oncology and urology at Case Western Reserve University School of Medicine in Cleveland. These data were presented by Dr. Ellis on behalf of Lee Ponsky MD, Associate Professor of Urology and principal investigator for this trial.

Dr. Ellis presented results from 20 patients at the American Society for Radiation Oncology annual meeting. The response rate suggests that patients reacted well and had acceptable levels of treatment-related toxicity following treatment. There were no reports of gastrointestinal or small bowel toxicity, or RCC-related deaths. For patients who underwent a post-treatment biopsy, incomplete or refractory treatment was found in 91%. “We still don’t know yet the optimal doses to achieve comparable efficacy to surgery or cryotherapy,” Dr. Ellis said.

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The 15 men and five women ranged from 58 to 92 years old (mean 80). The 20 patients received initial doses of 600 cGy per fraction for four fractions, followed by increments of 200 cGy per fraction to total doses of 24, 32, and 48 Gy in groups of four to six patients per dose level. 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.

Acute toxicity was limited to Grade 1 fatigue in two patients in the highest-dose treatment group, which was relieved by rest. Late toxicity occurred in two patients who experienced Grade 2 chronic renal insufficiency as demonstrated by elevated creatinine values (range 2-4 mg/dL).

“What was remarkably surprising was that we had very few, if any, side effects in these patients,” Dr. Ellis said.

All of the patients had biopsy or radiologically determined diagnosis of localized primary renal cancer and were considered poor surgical candidates. They were divided into four treatment groups (24, 32, 40, and 48 Gy). None of the patients had prior pelvic or abdominal radiation.

The tumor response rate was 94% across all treatment groups (all four patients in the 24 Gy group, all six in the 32 Gy group, two of three in the 40 Gy group, and all five in the 48 Gy group). The investigators defined tumor response rate as stable or reduced tumor volume on post-treatment imaging.

“The trial is ongoing and has been expanded to treat 12 additional patients in groups of four at 48, 54, and 20 Gy in three fractions, and we anticipate improved pathologic response rates at these doses to be higher. A multi-center trial would then be needed to confirm the findings,” Dr. Ellis said.