Erschienen in:
01.04.2015 | Original article
Dose-dependent changes in renal 1H-/23Na MRI after adjuvant radiochemotherapy for gastric cancer
verfasst von:
Stefan Haneder, MD, Johannes Michael Budjan, MD, Stefan Oswald Schoenberg, MD, Simon Konstandin, PhD, Lothar Rudi Schad, PhD, Ralf Dieter Hofheinz, MD, Veronika Gramlich, MSc, Frederik Wenz, MD, Frank Lohr, MD, Judit Boda-Heggemann, MD, PhD
Erschienen in:
Strahlentherapie und Onkologie
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Ausgabe 4/2015
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Abstract
Purpose
Combined radiochemotherapy (RCT) for gastric cancer with three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to the upper left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) allows kidney sparing despite improved target coverage. Renal function in long-term gastric cancer survivors was evaluated with 3T functional magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) and 23Na imaging.
Patients and methods
Five healthy volunteers and 13 patients after radiotherapy were included: 11×IG-IMRT; 1×3D-CRT; 1× “positive control” with stereotactic body radiotherapy (SBRT) of a metastasis between the spleen/left kidney. Radiation doses were documented for the upper/middle/lower kidney subvolumes. Late toxicity was evaluated based on CTC criteria, questionnaire, and creatinine values. Morphological sequences, DWI images, and 23Na images were acquired using a 1H/23Na-tuned body-coil before/after intravenous water load (WL). Statistics for [23Na] (concentration) and apparent diffusion coefficient (ADC) values were calculated for upper/middle/lower renal subvolumes. Corticomedullary [23Na] gradients and [23Na] differences after WL were determined.
Results
No major morphological alteration was detected in any patient. Minor scars were observed in the cranial subvolume of the left kidney of the 3D-CRT and the whole kidney of the control SBRT patient. All participants presented a corticomedullary [23Na] gradient. After WL, a significant physiological [23Na] gradient decrease (p < 0.001) was observed in all HV and IG-IMRT patients. In the cranial left kidney of the 3D-CRT patient and the positive control SBRT patient, the decrease was nonsignificant (p = 0.01, p = 0.02). ADC values were altered nonsignificantly in all renal subvolumes (all participants). Renal subvolumes with doses ≥ 35 Gy showed a reduced change of the [23Na] gradient after WL (p = 0.043). No participants showed clinical renal impairment.
Conclusions
Functional parameters of renal 23Na MRI after gastric IG-IMRT are identical to those of healthy volunteers, in contrast to renal subvolumes after ablative doses in the control and 3D-CRT patient. While kidney doses to the cortex below 20–25 Gy in fractional doses of ~ 1 Gy in IG-IMRT (combined with intensified chemotherapy) do not seem to cause significant MRI morphological or functional alterations, doses of > 35 Gy in 1.5–2 Gy fractions clearly result in impairment.