title: Phase II study of tailored chemotherapy for advanced colorectal cancer with either 5-fluouracil and leucovorin or oxaliplatin and irinotecan based on the expression of thymidylate synthase and dihydropyrimidine dehydrogenase.
abstract: BACKGROUND
  Thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) are essential enzymes for 5-fluorouracil (5-FU) metabolism. In patients with advanced colorectal cancer (ACRC), retrospective studies have shown that low expression levels of TS and DPD correlated with response to 5-FU. We performed a prospective study in which the choice of first-line chemotherapy with either 5-FU or a non-5-FU containing regimen was based on TS and DPD expression.
  
  
  METHODS
  Fresh-frozen samples of metastases were obtained from 58 previously untreated patients with ACRC. mRNA expression of TS and DPD was quantified using an RT-PCR assay. Patients with low tumor expression of both TS and DPD received weekly bolus 5-FU/leucovorin (LV) 500 mg/m2 (group A); patients with high TS and/or DPD received 3-weekly oxaliplatin 85 mg/m2 and irinotecan 200 mg/m2 (group B). After progression, cross-over to the alternative regimen was attempted.
  
  
  RESULTS
  Of 53 eligible patients, 31 had tumors with both low TS and low DPD, and were treated in group A. A response was observed in 11 patients [35%; 95% confidence interval (CI) 19% to 54%]. Cross-over to second-line oxaliplatin/irinotecan resulted in a partial response in two out of 16 patients (13%; 95% CI 1% to 38%). In group B, four out of 22 patients responded (18%; 95% CI 5% to 40%), while no responses were observed in 12 patients after cross-over to 5-FU/LV (0%; 95% CI 0% to 28%).
  
  
  CONCLUSIONS
  Prospective selection of 5-FU/LV chemotherapy based on low TS and DPD expression in patients with ACRC did not confirm the high response rates reported in retrospective studies. The procedure of obtaining metastatic tissue and quantitation of enzymes appeared feasible but cumbersome. Before assessing the clinical utility of a predictive marker in a randomized trial, future studies should focus on prospective validation of the assay in a large and well defined population.
authors.affiliation: Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: C H
authors.initials: CH
authors.lastname: Smorenburg
authors.forename: G J
authors.initials: GJ
authors.lastname: Peters
authors.forename: C J
authors.initials: CJ
authors.lastname: van Groeningen
authors.forename: P
authors.initials: P
authors.lastname: Noordhuis
authors.forename: K
authors.initials: K
authors.lastname: Smid
authors.forename: A M G H
authors.initials: AM
authors.lastname: van Riel
authors.forename: W
authors.initials: W
authors.lastname: Dercksen
authors.forename: H M
authors.initials: HM
authors.lastname: Pinedo
authors.forename: G
authors.initials: G
authors.lastname: Giaccone
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D000077146:Irinotecan; D002955:Leucovorin / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009944:Organoplatinum Compounds / Q000008:administration & dosage; D000077150:Oxaliplatin; D011379:Prognosis; D011446:Prospective Studies; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism*
chemical_list: D009944:Organoplatinum Compounds; D012333:RNA, Messenger; D000077150:Oxaliplatin; D000077146:Irinotecan; D042943:Dihydrouracil Dehydrogenase (NADP); D013940:Thymidylate Synthase; D002955:Leucovorin; D005472:Fluorouracil; D002166:Camptothecin