title: Local control rates of metastatic renal cell carcinoma (RCC) to the bone using stereotactic body radiation therapy: Is RCC truly radioresistant?
abstract: OBJECTIVE
  We report the radiographic and clinical response rate of stereotactic body radiation therapy (SBRT) compared with conventional fractionated external beam radiation therapy (CF-EBRT) for renal cell carcinoma (RCC) bone lesions treated at our institution.
  
  
  METHODS
  Forty-six consecutive patients were included in the study, with 95 total lesions treated (50 SBRT, 45 CF-EBRT). We included patients who had histologic confirmation of primary RCC and radiographic evidence of metastatic bone lesions. The most common SBRT regimen used was 27 Gy in 3 fractions.
  
  
  RESULTS
  Median follow-up was 10 months (range, 1-64 months). Median time to symptom control between SBRT and CF-EBRT were 2 (range, 0-6 weeks) and 4 weeks (range, 0-7 weeks), respectively. Symptom control rates with SBRT and CF-EBRT were significantly different (P = .020) with control rates at 10, 12, and 24 months of 74.9% versus 44.1%, 74.9% versus 39.9%, and 74.9% versus 35.7%, respectively. The median time to radiographic failure and unadjusted pain progression was 7 months in both groups. When controlling for gross tumor volume, dose per fraction, smoking, and the use of systemic therapy, biologically effective dose ≥80 Gy was significant for clinical response (hazard ratio [HR], 0.204; 95% confidence interval [CI], 0.043-0.963; P = .046) and radiographic (HR, 0.075; 95% CI, 0.013-0.430; P = .004). When controlling for gross tumor volume and total dose, biologically effective dose ≥80 Gy was again predictive of clinical local control (HR, 0.140; 95% CI, 0.025-0.787; P = .026). Toxicity rates were low and equivalent in both groups, with no grade 4 or 5 toxicity reported.
  
  
  CONCLUSIONS
  SBRT is both safe and effective for treating RCC bone metastases, with rapid improvement in symptoms after treatment and more durable clinical and radiographic response rate. Future prospective trials are needed to further define efficacy and toxicity of treatment, especially in the setting of targeted agents.
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Arya
authors.initials: A
authors.lastname: Amini
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Basel
authors.initials: B
authors.lastname: Altoos
authors.affiliation: Department of Medicine, Division of Medical Oncology, University of Colorado Denver, Aurora, Colorado.|Medical Oncology Department, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico.
authors.forename: Maria T
authors.initials: MT
authors.lastname: Bourlon
authors.affiliation: Department of Biostatistics and Bioinformatics Shared Resource, University of Colorado Denver, Aurora, Colorado.
authors.forename: Edward
authors.initials: E
authors.lastname: Bedrick
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Bhatia
authors.affiliation: Department of Medicine, Division of Medical Oncology, University of Colorado Denver, Aurora, Colorado.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Kessler
authors.affiliation: Department of Medicine, Division of Medical Oncology, University of Colorado Denver, Aurora, Colorado.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Flaig
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Fisher
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Kavanagh
authors.affiliation: Department of Medicine, Division of Medical Oncology, University of Colorado Denver, Aurora, Colorado.
authors.forename: Elaine T
authors.initials: ET
authors.lastname: Lam
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Sana D
authors.initials: SD
authors.lastname: Karam
mesh_terms: D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000517:prevention & control* / Q000556:secondary / Q000601:surgery*; D002292:Carcinoma, Renal Cell / Q000556:secondary / Q000601:surgery*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011836:Radiation Tolerance; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated