Could Recent Decreases in Breast Cancer Incidence Really Be Due to Lower HRT Use? Trends in Attributable Risk for Modifiable Breast Cancer Risk Factors in Canadian Women

By Neutel, C. Ineke; Morrison, Howard | Canadian Journal of Public Health, September/October 2010 | Go to article overview

Could Recent Decreases in Breast Cancer Incidence Really Be Due to Lower HRT Use? Trends in Attributable Risk for Modifiable Breast Cancer Risk Factors in Canadian Women


Neutel, C. Ineke, Morrison, Howard, Canadian Journal of Public Health


ABSTRACT

Objectives: Recent downward trends in breast cancer incidence have been attributed to declining use of hormone replacement therapy (HRT). To determine whether this is a credible conclusion, this study calculated population attributable risk (PAR) for HRT and other modifiable breast cancer risk factors.

Methods: PAR calculation needs both the prevalence of a risk factor, and the relative risk (RR) for breast cancer incidence for that risk factor. Prevalences were calculated for Canadian women, aged 50-69, participating in the National Population Health Survey, 1994-2006. RR were derived from published research: 1.4 for HRT use, 1.4 for excessive alcohol use, 1.15 for physical inactivity, 1.25 for smoking, 1.4 for BMI over 30 kg/m2. Trends for PAR were calculated for the risk factors separately, as well as combined. Age-adjusted breast cancer incidence rates were calculated for Canadian women aged 50-69 for the years 1994-2004.

Results: Between 1998 and 2004, PAR for HRT decreased by 50%. PAR for other risk factors showed only small changes, and the combined PAR decreased by 18.6%. Age-adjusted breast cancer incidence for women aged 50-69 peaked in 2000 at 330.0/100,000, then dropped by 17.2% by 2004.

Conclusion: Patterns of PAR for HRT use in Canada are consistent with the noticeable decrease in breast cancer incidence observed for women of the same age group. Combining PAR for all risk factors indicated that changes in HRT use overpowered any trends of other risk factors. The combined PAR suggest that alterations in lifestyle could have considerable impact on breast cancer incidence.

Key words: Breast cancer incidence; population attributable risk; hormone replacement therapy; alcohol; physical activity; obesity

La traduction du résumé se trouve à la fin de l'article. Can J Public Health 2010;101(4):405-9.

Many menopausal women have unpleasant symptoms which can be alleviated by hormone replacement therapy (HRT).1-3 For decades, the putative protective effects against heart disease and osteoporosis were also considered incentives for HRT use.4,5 When results from the Women's Health Initiative (WHI) and the Heart and Estrogen/progestin Replacement Study (HERS) provided no evidence for heart disease protection - in fact, even suggesting an increased risk6-8 - dramatic decreases in HRT use ensued.9-11

HRT use is also known to increase the risk of breast cancer. In many countries, breast cancer incidence appears to be on a downward trend in recent years. In Canada, age-adjusted incidence rates for breast cancer changed from a high of 105.1/100,000 in 1999 to a low of 96/100,000 after 2002.12 Similar decreases were seen for other countries.9,13,14 Because of HRT's known breast cancer risk, researchers were quick to attribute such declines in breast cancer rates to lower HRT use.15,16 Not all agreed.17,18

However, it is not clear whether a roughly 4% drop in overall breast cancer incidence is a drop of reasonable magnitude to be attributable to the observed decrease in HRT use. Population attributable risk (PAR) can be used to estimate the proportion of breast cancer incidence attributable to risk factors such as HRT. Accordingly, the objective of this study is to estimate trends in breast cancer PAR due to five modifiable breast cancer risk factors: HRT use, excessive alcohol consumption, obesity, lack of physical activity and smoking. Smoking is not as generally accepted as a breast cancer risk factor, but a recent Canadian expert panel concluded that there is a small, but real, increase.19

In order to estimate the PAR, risk measures for each of the risk factors are needed. Increases in breast cancer risk for HRT use varies with type of HRT used. For overall HRT use, breast cancer risk increased about 50%.15,16,20 For women taking the estrogen and progestin (E&P) combination, breast cancer risk doubled.15,16 The increased risk for unopposed estrogen varied from a high of an 80% increase to no effect at all. …

The rest of this article is only available to active members of Questia

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

Could Recent Decreases in Breast Cancer Incidence Really Be Due to Lower HRT Use? Trends in Attributable Risk for Modifiable Breast Cancer Risk Factors in Canadian Women
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Author Advanced search

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.