Renal radiosurgery: initial clinical experience with histological evaluation.

The purpose of this study was to determine whether radiosurgical technology can be safely applied to renal tumors. Patients received radiosurgical treatment of renal lesions. At 8 weeks after radiosurgical treatment, patients underwent a partial or radical nephrectomy and histologic evaluation. The patients received a radiation dose of 4 Gy per fraction for 4 fractions. Patients were followed, and radiation-induced toxicities were noted. Three patients were treated for a minimum of 1 year of follow-up. All patients completed the treatments, tolerating each of the 4 fractions with no adverse events. No acute toxicities or changes in renal function were noted. None of the patients had any evidence of acute radiation injury or toxicity noted at the time of surgery or within the subsequent 12 months after the radiosurgical treatment. The last patient treated was found to have a cavity with no microscopic evidence of viable tumor after radiosurgical treatment; pathology was consistent with necrotic renal cell carcinoma, papillary type. The other 2 tumors demonstrated pathologic evidence of viable renal cell carcinoma (grade I and grade II). Tumor size remained relatively unchanged for 8 weeks after the radiosurgical treatment in all patients. The authors are extremely encouraged and cautiously optimistic with the initial results. Radiosurgery for renal tumors appears to be safe at this initial dose level.