programma & abstracts - Nederlandse Vereniging voor Radiologie

Abdominale radiologie 1 1
Figure 1: A) T1-weighted images (T1W) acquired before, 30 s and 60 s after contrast agent (CA) administration, obtained for a patient with
rectal cancer during primary staging. Red line indicates the tumor boundaries. White arrows indicate different tissue components of the rectum.
T2W tumor image is shown as an image inset (upper left). B) Average signal enhancement-time curves obtained for the tumor (black line), rectal
muscle (red line), mucosa (green line) and mesorectal fat (blue line) in three patients. In patient 3, the delineation of ROIs in rectal muscle and
mucosa was not possible.
O1.7
ASSESSMENT OF A COMPLETE RESPONSE
OF RECTAL CANCER TO PREOPERATIVE
CHEMORADIATION THERAPY: A
COMPARISON BETWEEN MR VOLUMETRY
AND DIFFUSION-WEIGHTED MRI
D.M.J. Lambregts 1 , L. Curvo-Semedo 2 , M. Maas 1 ,
T. Thywissen 1 , G. Lammering 1 , G.L. Beets 1 , F. Caseiro-Alves 2 ,
R.G.H. Beets-Tan 1
1
Maastricht Universitair Medisch Centrum, Maastricht
2
Radiology University Clinic, Coimbra University Hospital,
Coimbra, Portugal
Purpose: To determine the performance of diffusion-weighted
MRI (DWI) in assessing a complete tumor response (CR) after
chemoradiation (CRT) in patients with locally advanced rectal
cancer (LARC) by means of [1] volumetric signal intensity and
[2] apparent diffusion coefficient (ADC) measurements, and to
compare its performance with volumetry on T2W-MRI.
Methods: Fifty LARC patients underwent standard T2W-FSE
and DWI (b0,500,1000) pre- and post-CRT. Two independent
readers retrospectively placed free-hand ROIs in each tumorslice
on both datasets to determine pre-CRT and post-CRT
tumor volumes and the tumor volume reduction (∆volume).
ROIs were copied to an ADC-map to calculate mean tumor
ADCs. Histology (ypT0) was the standard reference. ROCcurves
were generated to compare the performance of T2Wvolumetry,
DWI-volumetry and ADC in assessing a CR. The
intraclass correlation coefficient (ICC) was used to evaluate
interobserver variability and the correlation between T2Wvolumetry
and DWI-volumetry.
Results: Areas under the ROC-curve (AUC) for identification
of a CR based on pre-volume / post-volume / ∆volume were
0.57 / 0.70 / 0.84 for T2W-volumetry versus 0.63 / 0.93 / 0.92
for DWI-volumetry (p=0.15 / 0.02 / 0.42). For ADC, AUCs were
0.55, 0.54 and 0.51. Interobserver agreement was excellent for
all pre-CRT measurements (ICC 0.91-0.96) versus good (0.61-
0.79) post-CRT. The ICC between T2W- and DWI-volumetry
was excellent (0.97) pre-CRT versus fair (0.25) post-CRT.
Conclusion: Post-CRT DWI-volumetry provided a high diagnostic
performance is assessing a CR and was significantly
more accurate than T2W-volumetry. Post-CRT DWI was
equally accurate as ∆volume of both T2W-MRI and DWI. Pretreatment
volumetry and ADC were not reliable.
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