Side Effects Revealed: Women Share Their Experiences with Breast Cancer Drugs

July 1, 2008

Our Bodies Our Blog has invited the folks at Breast Cancer Action to write monthly guest posts on breast cancer and related issues.

by Pauli Ojea

Women facing a life-threatening illness like breast cancer often have very difficult decisions to make about whether they can live with the side effects of what could be a helpful drug. Deciding whether the benefits outweigh the risks can happen only if all the information on side effects is available. All too often it’s not.

In an effort to remedy this situation, Breast Cancer Action (BCA) just released a report on women’s experiences with side effects of aromatase inhibitors (AIs), a common class of drugs for breast cancer treatment. In doing so, we hope to encourage additional research on how AIs affect women.

For women living with estrogen-receptor-positive breast cancer, AIs are a relatively new class of drugs that have quickly become the standard of care. Limited information about AI side effects is available, but there’s still a lot we don’t know.

Arimidex, the first AI, was approved by the FDA in 1996 for breast cancer treatment. Soon after, BCA started hearing from women whose doctors were recommending Arimidex, asking what the known side effects were and how long they should stay on the drug.

Knowing that the FDA couldn’t — and the drug industry wouldn’t — collect this information in a way that’s helpful to patients, we decided to do it ourselves. We wanted to make sure that this information was being captured somewhere. So, with an online survey we launched in 2005, we began collecting information from women about their experience on the three AIs approved for use in breast cancer: anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin).

In 2007, we released a preliminary report based on the first 612 responses to the survey. Our new release, “Side Effects Revisited: Women’s Experiences with Aromatase Inhibitors,” is based on nearly 1,200 responses. The most common side effects reported continue to be hot flashes, bone pain, tiredness, muscle pain and insomnia. We also found that more than 25 percent of respondents experienced side effects so severe they decided to stop taking their AI. This is particularly troubling, because it means that the side effects were so bad that women felt they would rather risk a breast cancer recurrence than experience such poor quality of life.

The report also found that the women who took our survey (which is not necessarily a representative sample of all women taking an AI) are on average much younger than the women who have been studied in clinical trials of these drugs. These younger women — and by younger we mean under 60 — are experiencing more and worse side effects than older women on AIs. This is particularly true for younger women whose menopause was induced.

As a result, they’re experiencing very real quality-of-life issues that aren’t reflected in clinical trial data thus far. These results tell us that it will be crucial for future studies to look at how AIs are affecting younger women.

Here at BCA, we understand that patients almost always know before the medical community does what side effects they are experiencing. Through these reports on AI side effects, we hope to encourage additional research on the long-term side effects for all women taking these drugs. After all, this information is what allows people to make informed decisions about their health care — a value that’s critically important to all of us.

Pauli Ojea is the community organizer at Breast Cancer Action, where she mobilizes people to do something besides worry. Read BCA’s full report on women’s experiences with side effects of aromatase inhibitors, including quotes from the women themselves. Visit to join online discussions on the topic.

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