Does HRT influence the chance of a woman getting invasive breast cancer?

Refer to a study on hormone replacement therapy. Until 2002, hormone replacement therapy (HRT), taking hormones to replace those the body no longer makes after menopause, was commonly prescribed to post-menopausal women. However, in 2002 the results of a large clinical trial were published, causing most doctors to stop prescribing it and most women to stop using it, impacting the health of millions of women around the world. In the experiment, 8506 women were randomized to take HRT and 8102 were randomized to take a placebo. Table 6.16 shows the observed counts for several conditions over the five years of the study. (Note: The planned duration was 8.5 years. If Exercises 6.205 through 6.208 are done correctly, you will notice that several of the p-values are just below 0.05. The study was terminated as soon as HRT was shown to significantly increase risk (using a significance level of α = 0.05), because at that point it was unethical to continue forcing women to take HRT).

Table 6.16

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HRT Group Condition Placebo Group Cardiovascular Disease Invasive Breast Cancer Cancer (all) Fractures 164 122 166 502 650 124 458 788