title: Optimal time interval between capecitabine intake and radiotherapy in preoperative chemoradiation for locally advanced rectal cancer.
abstract: 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.
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
authors.forename: Chang Sik
authors.initials: CS
authors.lastname: Yu
authors.forename: Tae Won
authors.initials: TW
authors.lastname: Kim
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Won Sik
authors.initials: WS
authors.lastname: Choi
authors.forename: Hee Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Heung Moon
authors.initials: HM
authors.lastname: Chang
authors.forename: Min Hee
authors.initials: MH
authors.lastname: Ryu
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Jang
authors.forename: Seung Do
authors.initials: SD
authors.lastname: Ahn
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Lee
authors.forename: Seong Soo
authors.initials: SS
authors.lastname: Shin
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Choi
authors.forename: Jin Cheon
authors.initials: JC
authors.lastname: Kim
mesh_terms: 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
chemical_list: D000964:Antimetabolites, Antineoplastic; D003841:Deoxycytidine; D000069287:Capecitabine; D005472:Fluorouracil