Evaluation of early metabolic responses in rectal cancer during combined radiochemotherapy or radiotherapy alone: sequential FDG-PET-CT findings.
OBJECTIVE
The purpose of this study was to prospectively investigate metabolic changes of rectal tumors after 1 week of treatment of either radiochemotherapy (28 x 1.8 Gy+Capecitabine) (RCT) or hypofractionated radiotherapy (5 x 5 Gy) alone (RT).


METHODS
Fourty-six rectal cancer patients, 25 RCT- and 21 RT-patients, were included in this study. Sequential FDG-PET-CT scans were performed for each of the included patients both prior to treatment and after the first week of treatment. Consecutively, the metabolic treatment response of the tumor was evaluated.


RESULTS
For the patients referred for pre-operative RCT, significant reductions of SUV(mean) (p<0.001) and SUV(max) (p<0.001) within the tumor were found already after the first week of treatment (8 Gy biological equivalent dose (BED). In contrast, 1 week of treatment with RT alone did not result in significant changes in the metabolic activity of the tumor (p=0.767, p=0.434), despite the higher applied RT dose of 38.7 Gy BED.


CONCLUSIONS
Radiochemotherapy of rectal cancer leads to significant early changes in the metabolic activity of the tumor, which was not the case early after hypofractionated radiotherapy alone, despite the higher radiotherapy dose given. Thus, the chemotherapeutic agent Capecitabine might be responsible for the early metabolic treatment responses during radiochemotherapy in rectal cancer.
Janssen
Marco H M
MH
Department of Radiation Oncology (MAASTRO), University Medical Centre Maastricht, Maastricht, The Netherlands. marco.janssen@maastro.nl
Ollers
Michel C
MC
van Stiphout
Ruud G P M
RG
Buijsen
Jeroen
J
van den Bogaard
Jørgen
J
de Ruysscher
Dirk
D
Lambin
Philippe
P
Lammering
Guido
G
D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use; D000069287:Capecitabine; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000627:therapeutic use; D005260:Female; D019788:Fluorodeoxyglucose F18; D005472:Fluorouracil / Q000031:analogs & derivatives / Q000627:therapeutic use; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000378:metabolism* / Q000532:radiotherapy*; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
D000964:Antimetabolites, Antineoplastic; D019275:Radiopharmaceuticals; D003841:Deoxycytidine; D019788:Fluorodeoxyglucose F18; D000069287:Capecitabine; D005472:Fluorouracil