Dynamic contrast-enhanced magnetic resonance imaging of radiation therapy-induced microcirculation changes in rectal cancer.
OBJECTIVE
Dynamic contrast-enhanced T1-weighted magnetic resonance imaging (DCE-MRI) allows noninvasive evaluation of tumor microvasculature characteristics. This study evaluated radiation therapy related microvascular changes in locally advanced rectal cancer by DCE-MRI and histology.


METHODS
Dynamic contrast-enhanced-MRI was performed in 17 patients with primary rectal cancer. Seven patients underwent 25 fractions of 1.8 Gy radiation therapy (RT) (long RT) before DCE-MRI and 10 did not. Of these 10, 3 patients underwent five fractions of 5 Gy RT (short RT) in the week before surgery. The RT treated and nontreated groups were compared in terms of endothelial transfer coefficient (K(PS), measured by DCE-MRI), microvessel density (MVD) (scored by immunoreactivity to CD31 and CD34), and tumor cell and endothelial cell proliferation (scored by immunoreactivity to Ki67).


RESULTS
Tumor K(PS) was 77% (p = 0.03) lower in the RT-treated group. Histogram analyses showed that RT reduced both magnitude and intratumor heterogeneity of K(PS) (p = 0.01). MVD was significantly lower (37%, p = 0.03) in tumors treated with long RT than in nonirradiated tumors, but this was not the case with short RT. Endothelial cell proliferation was reduced with short RT (81%, p = 0.02) just before surgery, but not with long RT (p > 0.8). Tumor cell proliferation was reduced with both long (57%, p < 0.001) and short RT (52%, p = 0.002).


CONCLUSIONS
Dynamic contrast-enhanced-MRI-derived K(PS) values showed significant radiation therapy related reductions in microvessel blood flow in locally advanced rectal cancer. These findings may be useful in evaluating effects of radiation combination therapies (e.g., chemoradiation or RT combined with antiangiogenesis therapy), to account for effects of RT alone.
de Lussanet
Quido G
QG
Department of Radiology, Maastricht University Hospital, Maastricht, The Netherlands. qdlu@rdia.azm.nl
Backes
Walter H
WH
Griffioen
Arjan W
AW
Padhani
Anwar R
AR
Baeten
Coen I
CI
van Baardwijk
Angela
A
Lambin
Philippe
P
Beets
Geerard L
GL
van Engelshoven
Jos M A
JM
Beets-Tan
Regina G H
RG
D049109:Cell Proliferation / Q000528:radiation effects; D003287:Contrast Media; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008833:Microcirculation / Q000528:radiation effects; D008875:Middle Aged; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000098:blood supply* / Q000532:radiotherapy*
D003287:Contrast Media