Assessment of renal function after conformal radiotherapy and intensity-modulated radiotherapy by functional 1H-MRI and 23Na-MRI

Strahlenther Onkol. 2012 Dec;188(12):1146-54. doi: 10.1007/s00066-012-0254-5. Epub 2012 Nov 1.

Abstract

Purpose: Adjuvant radiochemotherapy (RCHT) improves survival of patients with locally advanced gastric cancer. Conventional three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to a significant amount of the left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) provides excellent target coverage with improved kidney sparing. Few long-term results on IMRT for gastric cancer, however, have been published. Functional magnetic resonance imaging (fMRI) at 3.0 T including blood oxygenation-level dependent (BOLD) imaging, diffusion-weighted imaging (DWI) and, for the first time, (23)Na imaging was used to evaluate renal status after radiotherapy with 3D-CRT or IG-IMRT.

Patients and methods: Four disease-free patients (2 after 3D-CRT and 2 after IMRT; FU for all patients > 5 years) were included in this feasibility study. Morphological sequences, axial DWI images, 2D-gradient echo (GRE)-BOLD images, and (23)Na images were acquired. Mean values/standard deviations for ((23)Na), the apparent diffusion coefficient (ADC), and R2* values were calculated for the upper/middle/lower parts of both kidneys. Corticomedullary (23)Na-concentration gradients were determined.

Results: Surprisingly, IG-IMRT patients showed no morphological alterations and no statistically significant differences of ADC and R2* values in all renal parts. Values for mean corticomedullary (23)Na-concentration matched those for healthy volunteers. Results were similar in 3D-CRT patients, except for the cranial part of the left kidney. This was atrophic and presented significantly reduced functional parameters (p = 0.001-p = 0.033). Reduced ADC values indicated reduced cell density and reduced extracellular space. Cortical and medullary R2* values of the left cranial kidney in the 3D-CRT group were higher, indicating more deoxygenated hemoglobin due to reduced blood flow/oxygenation. ((23)Na) of the renal cranial parts in the 3D-CRT group was significantly reduced, while the expected corticomedullary (23)Na-concentration gradient was partially conserved.

Conclusions: Functional MRI can assess postradiotherapeutic renal changes. As expected, marked morphological/functional effects were observed in high-dose areas (3D-CRT), while, unexpectedly, no alteration in kidney function was observed in IG-IMRT patients, supporting the hypothesis that reducing total/fractional dose to the renal parenchyma by IMRT is clinically beneficial.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Chemoradiotherapy, Adjuvant*
  • Diffusion Magnetic Resonance Imaging / methods*
  • Disease-Free Survival
  • Feasibility Studies
  • Female
  • Follow-Up Studies
  • Humans
  • Image Enhancement / methods*
  • Image Interpretation, Computer-Assisted / methods*
  • Kidney / radiation effects*
  • Kidney Function Tests*
  • Magnetic Resonance Imaging / methods*
  • Male
  • Middle Aged
  • Neoplasm Staging
  • Oxygen / blood*
  • Radiation Dosage
  • Radiation Injuries / diagnosis*
  • Radiotherapy Planning, Computer-Assisted / methods
  • Radiotherapy, Conformal*
  • Radiotherapy, Intensity-Modulated*
  • Stomach Neoplasms / mortality
  • Stomach Neoplasms / pathology
  • Stomach Neoplasms / radiotherapy*

Substances

  • Oxygen