title: Correlation of tumour response with starting tumour size and dose of tamoxifen in an N-methyl-N-nitrosourea (NMU)-induced rat mammary cancer model.
abstract: BACKGROUND
  The aim of this preliminary study was to address variations of responses observed with different starting tumor sizes of 10 and 15 mm, and the effects of different doses of tamoxifen (TAM) on experimental rat mammary tumors.
  
  
  METHODS
  Thirty-five inbred female Sprague Dawley rats aged 43 days were administered with three weekly doses of N-methyl-N-nitrosourea (NMU) intraperitoneally (ip) at 50 mg/kg body weight. Animals were randomized (beginning from 10 mm tumor size) into four TAM-treated (50, 100, 200 and 500 μg/day) groups of six animals each, and another group (n=6) treated with TAM 100 μg/day at starting tumour size of 15 mm. The animals were treated by oral gavage daily for 8 weeks before sacrifice.
  
  
  RESULTS
  Serum urea and creatinine, and overall physical tumor burden were significantly modulated in animals treated with variable doses of TAM compared to the untreated controls (n=5). Final body weight and tumor number were significantly different in the 10 mm-treated animals compared to those treated at 15 mm. There were no significant differences in histopathological features among all the groups.
  
  
  CONCLUSIONS
  Our findings suggest the importance of standardizing tumour size and drug doses before initiation of treatment, particularly in the direct comparison of basic end-tumour physical parameters.
authors.affiliation: Departments of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Malaysia E-mail : niksoriani@usm.my.
authors.forename: Hassan Muhammad
authors.initials: HM
authors.lastname: Yankuzo
authors.forename: Sharifah Tuan Sheriff
authors.initials: ST
authors.lastname: Emilia
authors.forename: Rumaizi
authors.initials: R
authors.lastname: Shaari
authors.forename: Nik Soriani
authors.initials: NS
authors.lastname: Yaacob
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003404:Creatinine / Q000097:blood; D054796:Drug Dosage Calculations; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000188:drug therapy*; D008770:Methylnitrosourea; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013629:Tamoxifen / Q000627:therapeutic use*; D016896:Treatment Outcome; D047368:Tumor Burden / Q000187:drug effects; D014508:Urea / Q000097:blood
chemical_list: D013629:Tamoxifen; D008770:Methylnitrosourea; D014508:Urea; D003404:Creatinine