title: Longitudinal analysis of mammary cancer multiplicity in chemoprevention studies.
abstract: BACKGROUND
  The effect of chemopreventive agents on cancer multiplicity is of primary interest in animal studies. The nature of data collected from chemoprevention studies may be analyzed by a longitudinal analysis of repeatedly measured cancer multiplicity data.
  
  
  METHODS
  We determined the number of mammary cancers over the entire follow-up period for varying doses of two chemopreventive agents. Longitudinal analyses were performed to model the number of cancers over different time intervals.
  
  
  RESULTS
  There was a significant increase in the number of cancers between six to seven weeks post-carcinogen administration in the control group. Varying patterns of cancer development were observed at different doses of chemopreventive agents including a delay in onset of tumor growth compared to the control group.
  
  
  CONCLUSIONS
  Longitudinal data analysis complements traditional analyses by providing detailed information regarding the effect of chemopreventive agents on the pattern of tumor development throughout the follow-up period. Importantly, some chemopreventive agents may delay time to appearance of mammary cancers without causing a significant difference in cancer multiplicity.
authors.affiliation: Biostatistics Unit, University of Alabama at Birmingham 35294, USA. hlweiss@uab.edu
authors.forename: H L
authors.initials: HL
authors.lastname: Weiss
authors.forename: C
authors.initials: C
authors.lastname: Rodríguez-Burford
authors.forename: C J
authors.initials: CJ
authors.lastname: Grubbs
authors.forename: W E
authors.initials: WE
authors.lastname: Grizzle
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D004224:Diterpenes; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000473:pathology / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000084562:Retinyl Esters; D013997:Time Factors; D014230:Triazoles / Q000494:pharmacology; D014801:Vitamin A / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D016588:Anticarcinogenic Agents; D004224:Diterpenes; D000084562:Retinyl Esters; D014230:Triazoles; D014801:Vitamin A; C060523:vorozole; C031469:anhydrovitamin A; C009166:retinol acetate