Re-analysis of the women's health initiative: breast cancer and its associations with post-menopausal hormone replacement therapy, reproductive history, and lifestyle
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Abstract
After the publication of the principal, or primary, results from the WHI, there were a large number of surprises in the findings, as well as a fair amount of controversy surrounding the conclusions. Because of the expansive breadth and importance of this study, a comprehensive compiling of all of the important re-analyses of the study, followed by more analyses, seemed pertinent to the scientific community. The entirety of the WHI focused on a large variety of chronic illnesses that post-menopausal women face but this paper will focus on the modifiable and non-modifiable risk factors important in the development and etiology of breast cancer. An in-depth review of the principal results regarding breast cancer from the WHI was undertaken, followed by a large and comprehensive compilation, review, and analysis of all the secondary analyses of the WHI principal data with the intent of verifying or disqualifying, via a mass of statistical analyses and long term observational studies, the conclusions drawn by the WHI investigators. After the aforementioned steps were taken, it was concluded by the author of this paper that the combined post-menopausal hormone regimen, as seen in the WHI Combined Hormone Trial, does pose serious risks in terms of increasing the hazard ratio for developing breast cancer, even for a short period of use, especially if multiple bouts are undertaken, confirming the conclusions from the WHI. Secondly, it was concluded by the author of this paper that the use of unopposed estrogen during a women's postmenopausal years does not increase one's risk for the development of breast cancer, only if initiated at least 5 years beyond menopause. These results were in major disagreement with the results from many other large studies, including the Million Women Study and the Collaborative Re-Analysis. The WHI Dietary Modification Trial was a huge success, despite the conclusions from the WHI attesting otherwise. In the Dietary Modification Trial, the WHI reasoned that the trial had no real effect due to a p-value of 0.07, despite overwhelming statistical and clinical evidence that it was indeed having a real effect. Implementing a low fat diet and increasing fruit, grain, and vegetable intake will lower a post-menopausal woman's hazard ratio for developing breast cancer and be further recommended to any woman, at any age. Lastly, the WHI principal results from their physical activity analysis concluded that regular physical activity will decrease a woman's hazard ratio for the development of breast cancer and this conclusion was reaffirmed by a large number of secondary analyses. Regular physical activity, assessed from nearly every angle, of any type, but regularly, will reduce the risk for the development of breast cancer, manifested through, for example, reductions in serum estradiol and body mass index. This lengthily study readily and efficiently addressed risk factors for breast cancer development and provided a large volume of data for future analysis as well. The conclusions made in this paper, as previously eluded to, make very clear the risk of combined hormone use and the many benefits of physical activity, for example. With these conclusions, both woman and physicians can harness the knowledge here and implement changes within their own life or how they practice and approach post-menopausal women's health, leading to longer and healthier years for post-menopausal women.
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Thesis (M.A.)--Boston University
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