High Estrogen Levels May Lead to Recurrence

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A study found that women diagnosed with early-stage breast cancer that came back (recurred) had higher blood estrogen levels than women diagnosed with early-stage cancer that didn't come back. Estrogen can encourage breast cancers to grow, especially cancers that are hormone-receptor positive, so the link between higher estrogen levels and breast cancer recurrence makes sense.

Many of the women in the study received the hormonal therapy medicine tamoxifen after their main treatment. Tamoxifen lowers the risk of hormone-receptor-positive cancer coming back. Tamoxifen works by blocking the effects of estrogen on breast cancer cells. While tamoxifen is very good, it can't block all the estrogen that can promote breast cancer growth. Breast cancer may sometimes come back even when a woman takes tamoxifen exactly as prescribed. Having high estrogen levels may be part of the reason why.

At the time the study was done, tamoxifen was the main hormonal therapy medicine used to reduce the risk of hormone-receptor-positive early-stage breast cancer coming back. Today, another type of hormonal therapy -- an aromatase inhibitor -- is available to reduce the risk recurrence in postmenopausal women. The aromatase inhibitors are: Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole). Aromatase inhibitors help stop breast cancer from coming back by preventing the formation of estrogen.

Because these two types of hormonal therapy medicines work differently, each one has different side effects. Aromatase inhibitor side effects include muscle and joint aches and pains. Aromatase inhibitors also can weaken bones, cause osteoporosis, and increase the risk of breaking a bone. Tamoxifen can actually strengthen bones, but many women taking tamoxifen have troublesome hot flashes.

Aromatase inhibitors are believed to be slightly better than tamoxifen for reducing the risk of recurrence. Still, tamoxifen is a good choice for many women.

If you've been treated for hormone-receptor-positive early-stage breast cancer, talk to your doctor about the suggested link between estrogen levels and breast cancer recurrence and steps you can take to reduce your risk of recurrence:

  • Make exercise a part of daily routine. Regular, moderate exercise (brisk walking, for example) has been shown to lower estrogen levels.
  • Eat a diet that's high in fruits and vegetables and low in saturated fats, and maintain a healthy weight. Having extra body fat may contribute to breast cancer recurrence risk, in part because estrogen can build up in body fat.
  • If you've been prescribed hormonal therapy medicine, be sure to take it as prescribed. Whether you're taking tamoxifen or an aromatase inhibitor, hormonal therapy is your best defense against the possibility of estrogen causing a recurrence.

Talk to your doctor about any obstacles that might stop you from doing all you can to lower your recurrence risk. If you have unpleasant side effects from hormonal therapy, ask about ways to manage them. You may be able to switch to a different hormonal therapy. Together, you and your doctor can develop a recurrence risk reduction plan that's right for YOU.

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