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Updated: Aug 19, 2026
Changes in Mammary Gland Morphology and Breast Cancer Risk in Rats
Published on: October 17, 2010
Longitudinal analysis of mammary cancer multiplicity in chemoprevention studies
H L Weiss1, C Rodríguez-Burford, C J Grubbs
1Biostatistics Unit, University of Alabama at Birmingham 35294, USA. hlweiss@uab.edu
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.
Conclusion:
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.
