Breast cancer and hormone therapy -- A looking-gla...( people carrying a lighter in their poc...)

people carrying a lighter in their pocket does not mean that lighters cause lung cancer. Thus, having two parallel time trends, for breast cancer incidence and for hormone use, still makes it necessary to investigate further in order to better understand if and how those trends could be linked. For example, a third important player has now been added, namely the rate of mammography screening, which has proved to have similar fluctuations as HT use and breast cancer incidence1. According to the Kaiser Permanente registry[1], the rate of women aged 4559 undergoing screening mammography in 20022004 (post-WHI period) decreased from 48% to 44%. Thus, awareness of the need for periodic breast examinations may ease, and the likelihood of women coming to be examined may decrease in a population that uses HT less frequently, which could lead to under-diagnosis of breast cancer.

On the other hand, the 28% increase in breast cancer incidence between the early 1980s and the early 1990s observed in the Kaiser Permanente cohort probably reflects the outcome of implementation of the mammography screening program during that period. The largest group among HT users in most of the countries (excluding the USA) has always been women younger than 60 years. The Kaiser Permanente data show that, for women aged 4559, the 70% drop in HT use (defined as dispensation of at least one hormonal prescription) in the year 2006 (post-WHI period) as compared to the year 2000 (pre-WHI period) was associated with a non-significant decrease of 4.9% in breast cancer incidence, which translates into a reduction of less than one case of breast cancer per 10,000 women per year. Furthermore, a welcome but unexplained fact is that, in younger women (age groups < 45 years and 4559 years), the incidence of invasive breast cancer started to decrease before the year 2000 (see Figure 1 in Glass et al.[1]). The same has been shown for the incidence of localized cancers (Figure 2[1]) and the age-adjus
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Contact: Jean Wright
jwright.ims@btopenworld.com
International Menopause Society
24-Jul-2007

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