title: Fulvestrant, an estrogen receptor downregulator, reduces cell turnover index more effectively than tamoxifen.
abstract: BACKGROUND
  This study was performed to determine whether drug action on breast tumours could also be analysed using a cell turnover index (CTI), a composite measurement of both proliferation and apoptosis.
  
  
  METHODS
  Data were obtained from a randomized, placebo-controlled trial comparing three single doses (50, 125 and 250 mg) of intramuscular fulvestrant (Faslodex, previously known as ICI 182,780) with oral tamoxifen 20 mg/day for 14-21 days in women with early, operable, ER-positive breast cancer. CTI was calculated as the ratio of the proliferation index to the apoptotic index.
  
  
  RESULTS
  Fulvestrant 250 mg significantly reduced CTI compared with both placebo (p = 0.0003) and tamoxifen (p = 0.026). The effect on CTI with tamoxifen was not significantly different from that with placebo.
  
  
  CONCLUSIONS
  This study suggests that CTI may be a useful indicator of drug action on breast tumour growth. A significant reduction in growth was found with fulvestrant 250 mg compared with tamoxifen.
authors.affiliation: Department of Surgery, South Manchester University Hospital Education and Research Centre, UK. bundredn@man.ac.uk
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Bundred
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Anderson
authors.forename: Robert I
authors.initials: RI
authors.lastname: Nicholson
authors.forename: Mitchell
authors.initials: M
authors.lastname: Dowsett
authors.forename: Michael
authors.initials: M
authors.lastname: Dixon
authors.forename: John F
authors.initials: JF
authors.lastname: Robertson
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects*; D004958:Estradiol / Q000031:analogs & derivatives / Q000627:therapeutic use*; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D019394:Ki-67 Antigen / Q000032:analysis; D007700:Kinetics; D010919:Placebos; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D020847:Estrogen Receptor Modulators; D019394:Ki-67 Antigen; D010919:Placebos; D013629:Tamoxifen; D000077267:Fulvestrant; D004958:Estradiol