Tumor perfusion increases during hypofractionated short-course radiotherapy in rectal cancer: sequential perfusion-CT findings.
OBJECTIVE
The purpose of this study was to investigate perfusion of rectal tumors and to determine early responses to short-course hypofractionated radiotherapy (RT).


METHODS
Twenty-three rectal cancer patients were included, which underwent perfusion-CT imaging before (pre-scan) and after treatment (post-scan). Contrast-enhancement was measured in tumor and muscle tissues and in the external iliac artery. Perfusion was quantified with three pharmacokinetic parameters: K(trans), v(e) and v(p). Perfusion differences between tumor and normal tissue and changes of the pharmacokinetic parameters between both scans were evaluated.


RESULTS
The median tumors K(trans) values increased significantly from the pre-scan (0.36+/-0.11 (min(-1))) to the post-scan (0.44+/-0.13 (min(-1))) (p<0.001). Also, histogram analysis showed a shift of tumor voxels from lower K(trans) values towards higher K(trans) values. Furthermore, the median K(trans) values were significantly higher for tumor than for muscle tissue on both the pre-scan (0.10+/-0.05 (min(-1)), p<0.001) and the post-scan (0.10+/-0.04 (min(-1)), p<0.001). In contrast, no differences between tumor and muscle tissues were found for v(e) and v(p). Also, no significant differences were observed for v(e) and v(p) between the two pCT-imaging time-points.


CONCLUSIONS
Hypofractionated radiotherapy of rectal cancer leads to an increased tumor perfusion as reflected by an elevated K(trans), possibly improving the bioavailability of cytotoxic agents in rectal tumors, often administered early after radiotherapy treatment.
Janssen
Marco H M
MH
Department of Radiation Oncology (MAASTRO), Maastricht University Medical Center (MUMC+), Maastricht, The Netherlands. marco.janssen@maastro.nl
Aerts
Hugo J W L
HJ
Kierkels
Roel G J
RG
Backes
Walter H
WH
Ollers
Michel C
MC
Buijsen
Jeroen
J
Lambin
Philippe
P
Lammering
Guido
G
D003287:Contrast Media / Q000493:pharmacokinetics; D019583:Dose Fractionation, Radiation; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D021621:Imaging, Three-Dimensional; D007472:Iohexol / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D008297:Male; D009367:Neoplasm Staging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D018709:Statistics, Nonparametric; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C093233:iobitridol; D007472:Iohexol