Leading Breast Cancer Researcher And Study Co-Author Rowan T. Chlebowski Explains Seemingly Contradictory Findings On Estrogen And Breast Cancer

Rowan T. Chlebowski, M.D., Ph.D., a principal investigator at the Los Angeles Biomedical Research Institute (LA BioMed), provided his assessment of the seeming contradictions between a previous Women's Health Initiative (WHI) study and a new abstract to be presented June 4 at the 2011 American Society of Clinical Oncology.



The abstract reports on the National Cancer Institute of Canada MAP.3 trial, the first study to evaluate an aromatase inhibitor for primary breast cancer prevention. Aromatase inhibitors lower the amount of estrogen in the body and are used for advanced and adjuvant breast cancer management in postmenopausal women. In the MAP.3 trial, the aromatase inhibitor exemestane reduced breast cancer incidence by a statistically significant 65% (P=0.002).



Dr Chlebowski, a co-author of the MAP.3 study, also was a co-author of a WHI report in JAMA this year on April 6th which provided updated follow-up of the WHI trial evaluating estrogen alone in post-menopausal women with prior hysterectomy. There, estrogen addition, as conjugated equine estrogens, surprisingly resulted in a statistically significant 23% reduction in breast cancer incidence (P=0.02).



Dr. Chlebowski noted "it seems paradoxical that both estrogen reduction with exemestane and estrogen addition result in lower breast cancer incidence but there is supportive underlying biology. Apparently, breast cancers which are driven by estrogen can only tolerate estrogen levels in a fairly narrow range. Thus, substantial change in the estrogen environment in either direction can influence breast cancer growth."



Dr. Chlebowski is a medical oncologist who has led several prior reports focusing on hormone effects on malignancies, including breast, lung and colorectal cancer.


Source
LA BioMed