title: Effect of Stereotactic Body Radiotherapy on the Growth Kinetics and Enhancement Pattern of Primary Renal Tumors.
abstract: OBJECTIVE
  The objective of our study was to assess the growth rate and enhancement of renal masses before and after treatment with stereotactic body radiotherapy (SBRT).
  
  
  METHODS
  This retrospective study included all patients with renal masses who underwent SBRT during a 5-year period. Orthogonal measurements of renal masses were obtained on pre- and posttreatment CT or MRI. Pre- and posttreatment growth rates were compared for renal mass diameter and volume using the t test. Pre- and posttreatment tumor enhancement values were compared for tumors that underwent multiphasic contrast-enhanced MRI.
  
  
  RESULTS
  Forty patients underwent SBRT for the treatment of 41 renal tumors: clear cell renal cell carcinomas (RCCs) (n = 16), papillary RCCs (n = 6), oncocytic neoplasms (n = 8), unclassified RCCs (n = 2), urothelial carcinoma (n = 1), and no pathologic diagnosis (n = 8). The mean maximum tumor diameter before treatment was 3.9 cm (range, 1.6-8.3 cm). Three hundred thirty-eight pre- and posttreatment imaging studies were analyzed: 214 MRI studies and 124 CT studies. The mean pre- and posttreatment lengths of observation were 416 days (range, 2-1800 days) and 561 days (83-1366 days), respectively. The mean pretreatment tumor growth rate of 0.68 cm/y decreased to -0.37 cm/y post treatment (p < 0.0001), and the mean tumor volume growth rate of 21.2 cm(3)/y before treatment decreased to -5.35 cm(3)/y after treatment (p = 0.002). Local control-defined as less than 5 mm of growth-was achieved in 38 of 41 (92.7%) tumors. The Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 showed progression in one tumor (2.4%), stability in 31 tumors (75.6%), partial response in eight tumors (19.5%), and complete response in one tumor (2.4%). No statistically significant change in tumor enhancement was shown (mean follow-up, 142 days; range, 7-581 days).
  
  
  CONCLUSIONS
  Renal tumors treated with SBRT show statistically significant reductions in growth rate and tumor size after treatment but do not show statistically significant differences in enhancement in the initial (mean, 142 days) posttreatment period.
authors.affiliation: 1 Department of Radiology, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Ave, CCW 3rd Fl, Boston, MA 02215.
authors.forename: Maryellen R M
authors.initials: MR
authors.lastname: Sun
authors.affiliation: 1 Department of Radiology, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Ave, CCW 3rd Fl, Boston, MA 02215.
authors.forename: Alexander
authors.initials: A
authors.lastname: Brook
authors.affiliation: 1 Department of Radiology, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Ave, CCW 3rd Fl, Boston, MA 02215.|2 Present address: Specialized Medical Imaging, Good Samaritan Medical Center, Brockton, MA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Powell
authors.affiliation: 1 Department of Radiology, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Ave, CCW 3rd Fl, Boston, MA 02215.|3 Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT.
authors.forename: Krithica
authors.initials: K
authors.lastname: Kaliannan
authors.affiliation: 4 Department of Urology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Wagner
authors.affiliation: 5 Department of Radiation Oncology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA.
authors.forename: Irving D
authors.initials: ID
authors.lastname: Kaplan
authors.affiliation: 6 Department of Radiology, Advanced Imaging Research Center, and Kidney Cancer Program, UT Southwestern Medical Center, Dallas, TX.
authors.forename: Ivan
authors.initials: I
authors.lastname: Pedrosa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000503:physiopathology* / Q000532:radiotherapy*; D007700:Kinetics; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
keywords: renal masses; stereotactic body radiotherapy (SBRT); tumor response