Optimal time interval between capecitabine intake and radiotherapy in preoperative chemoradiation for locally advanced rectal cancer.
OBJECTIVE
Capecitabine and its metabolites reach peak plasma concentrations 1 to 2 hours after a single oral administration, and concentrations rapidly decrease thereafter. We performed a retrospective analysis to find the optimal time interval between capecitabine administration and radiotherapy for rectal cancer.


METHODS
The time interval between capecitabine intake and radiotherapy was measured in patients who were treated with preoperative radiotherapy and concurrent capecitabine for rectal cancer. Patients were classified into the following groups. Group A1 included patients who took capecitabine 1 hour before radiotherapy, and Group B1 included all other patients. Group B1 was then subdivided into Group A2 (patients who took capecitabine 2 hours before radiotherapy) and Group B2. Group B2 was further divided into Group A3 and Group B3 with the same method. Total mesorectal excision was performed 6 weeks after completion of chemoradiation and the pathologic response was evaluated.


RESULTS
A total of 200 patients were enrolled in this study. Pathologic examination showed that Group A1 had higher rates of complete regression of primary tumors in the rectum (23.5% vs. 9.6%, p = 0.01), good response (44.7% vs. 25.2%, p = 0.006), and lower T stages (p = 0.021) compared with Group B1; however, Groups A2 and A3 did not show any improvement compared with Groups B2 and B3. Multivariate analysis showed that increases in primary tumors in the rectum and good response were only significant when capecitabine was administered 1 hour before radiotherapy.


CONCLUSIONS
In preoperative chemoradiotherapy for rectal cancer, the pathologic response could be improved by administering capecitabine 1 hour before radiotherapy.
Yu
Chang Sik
CS
Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
Kim
Tae Won
TW
Kim
Jong Hoon
JH
Choi
Won Sik
WS
Kim
Hee Cheol
HC
Chang
Heung Moon
HM
Ryu
Min Hee
MH
Jang
Se Jin
SJ
Ahn
Seung Do
SD
Lee
Sang-Wook
SW
Shin
Seong Soo
SS
Choi
Eun Kyung
EK
Kim
Jin Cheon
JC
D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage*; D000069287:Capecitabine; D003131:Combined Modality Therapy; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004334:Drug Administration Schedule; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012004:Rectal Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D012074:Remission Induction; D012189:Retrospective Studies
D000964:Antimetabolites, Antineoplastic; D003841:Deoxycytidine; D000069287:Capecitabine; D005472:Fluorouracil