Important Correction to BCA’s Aromatase Inhibitor Side Effects Report

Dear BCA Source Readers,

In our last newsletter, we ran an article about our report on women’s experiences with aromatase inhibitor side effects. With deep regret we inform you that some of the information in the report, as we first published it, is incorrect. We recently discovered an error with some of the data.

The error involves the number of women who experienced each side effect and to what degree of severity. The initial report that a large number of women had reported experiencing a stroke was understandably a cause for alarm. That information was wrong. The corrected data show that only 0.1 percent (1 respondent out of 612) reported stroke. We had first reported that side effects reported by more than half of the respondents to our online survey included stroke, cough, swelling of the arms and legs, flu-like symptoms, and anxiety. The corrected information is as follows: The side effects reported by more than half of the survey respondents were hot flashes, bone pain, feeling tired, muscle pain, and insomnia.

We take this error very seriously, as we are absolutely committed to seeing that women with breast cancer have accurate information so they can make the best decisions for themselves. We also offer our deepest apologies for the misinformation and for the anguish it may have caused. We have made the necessary corrections to the report and the survey and continue working to disseminate the updated information. We sent notices of correction to the press, individuals, and organizations that received the original report. We have also provided the corrected information to various online sources that posted articles about this report. If you are aware of places that do not have the corrected information, please let us know.

If you have questions or concerns, please feel free to contact us via e-mail,, or phone, 877/2-STOP-BC. The corrected report is available online. The content of the aromatase inhibitor report remains vitally important because it tells the story of women’s experiences with the side effects of these increasingly commonly used drugs. We will continue to collect side effect information on these drugs and will report future findings. Below is a corrected version of the newsletter article about the report that we first printed in the December 2006 issue of the BCA Source.


Barbara Brenner, Executive Director

by Brenda Salgado

Women like Sue (name changed for privacy) have been on my mind lately. They are a daily reminder to me of why Breast Cancer Action is doing the work that it does. Sue contacted me in 2005 after taking BCA’s Aromatase Inhibitors (AI) Side Effects Survey. “I’m happy these drugs are available, but women are entitled to know what they’re in for and make an informed decision accordingly,” she wrote.

Aromatase inhibitors are a type of hormonal treatment for postmenopausal women with breast cancer. Three AIs are currently approved for use by the U.S. Food and Drug Administration (FDA): anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara). Many breast tumors are estrogen-receptor-positive, meaning the hormone estrogen helps them to grow. AIs can help block the growth of these tumors in postmenopausal women by lowering the amount of estrogen in the body. Sue has suffered from extensive hair loss, which she believes is due to the AI she is taking. At first her doctor dismissed her concerns that the hair loss was due to the drug, but he later admitted to her that other women were experiencing the same effect. In our survey, over 30 percent of respondents reported hair thinning as a side effect, so clearly Sue is not alone. Sue’s doctor told her to “cheer up” because it would grow back after treatment, but Sue knows there is no research at this point to indicate whether that is true or not. Sue says her “concern is that doctors should advise their patients…about all side effects…and that research into side effects should continue, not cease as soon as the drugs hit the market, which seems to be the case these days.”

Breast Cancer Action launched its online survey of AI side effects in August 2005 to collect information on what women are experiencing while taking these powerful drugs. The survey includes questions about the respondent’s age, menopausal status at the time of prescription, AI prescribed, date started, and date stopped (if applicable). Respondents also rated a list of 38 side effects for severity and were asked to report any additional side effects. (The list of 38 side effects was generated from FDA product information documents for the three AIs.) BCA has compiled data from the survey in a report, Side Effects Revealed: Women’s Experiences with Aromatase Inhibitors. The sample of respondents is self-selected. As a result, the population of survey respondents is not representative of all women taking AIs. The initial results of the survey show that the vast majority of respondents (96 percent) reported at least one side effect. The side effects experienced by over 50 percent of respondents were hot flashes (65 percent), bone pain (64 percent), feeling tired (59 percent), muscle pain (58 percent), and insomnia (51 percent). Many women reported side effects not included on our list, including joint-related side effects, vaginal atrophy and dryness, a rise in cholesterol levels, and general pain. Several respondents also reported neurological, bone-related, and muscular side effects as well as feeling very aged.

About 30 percent of the respondents discontinued the use of an AI, 84 percent because of side effects they were experiencing and almost half of those (47 percent) specifically because of joint-related side effects. Over one-third (37 percent) of respondents reported receiving no information from their doctors about short-term side effects. Nearly two-thirds (63 percent) reported receiving no information from their doctors about long-term side effects. However, because AIs are relatively new breast cancer drugs, little information is available to doctors and patients about their long-term side effects. Several respondents also shared that they felt frustrated about not receiving side effect information from their doctors and having their concerns about side effects dismissed.

It’s clear from BCA’s report that several of a wide range of side effects are quite common. Additionally, although AIs are approved for use only in postmenopausal women with breast cancer, based on women’s responses, it is apparent that some premenopausal women are being prescribed AIs. More than half (54 percent) of the survey respondents reported that their menopause was not naturally occurring. For these women, menopause was either pharmaceutically or surgically induced.

The survey data clearly suggest that patients, when deciding whether or not to take AIs, need better information about the side effects of AIs and whether the use of AIs is actually appropriate for them.


BCA has three recommendations based on the findings of its survey.

  1. Conduct additional research on short-term and long-term side
  2. Provide the results of this research to doctors and patients.
  3. Use caution when prescribing AIs to perimenopausal women, as well as to premenopausal women who have been rendered menopausal by chemotherapy or ovarian function suppression.


Currently AIs are only approved for women who have been diagnosed with breast cancer. However, trials are already underway, looking at the use of AIs in women who have not had breast cancer but who are considered at “high-risk” for the disease. BCA has deep concerns about the use of pills for so-called prevention of breast cancer in healthy women.

Sue believes the AI Side Effects Survey findings will be important for “high risk” healthy women as well as for women with breast cancer. She says that, as this information comes to light and is made public, “many ‘well’ women will not want to try these drugs and risk the significant side effects.”

Breast Cancer Action has dedicated its report to the hundreds of women like Sue who generously took the time to respond to its Aromatase Inhibitors Side Effects Survey and to everyone who seeks to make informed decisions about the care they receive.

Brenda Salgado is BCA’s program manager and co-author of the AI side effects report.


I Three Phase III trials are currently looking at the use of exemestane in premenopausal women whose ovarian function has been surpressed either surgically, pharmaceutically, or through radiation of the ovaries. These trials were started in 2003, and results will not be available for several years. Until these trials are completed, no data exist to suggest that AIs are appropriate for use in women in whom menopause has been artificially induced.

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