Lower Risk for Non-Estrogen-Related Breast Cancer Recurrence

Recent studies may lead to lower breast cancer recurrence.

The American Cancer Society's deputy chief medical officer, Dr. Len Lichtenfield, has said that about one-third of women past menopause develop estrogen-receptor-negative breast tumors. The organization Life After Early Breast Cancer—or Life ABC—reports that recent studies suggest use of the estrogen-blocker tamoxifen may lower recurrence risk in both ER-positive and ER-negative breast cancer sufferers for the short term but perhaps not for the long term.



More than half of breast cancers are "fueled by estrogen," according to the National Cancer Institute, and tumors that are either "node-negative"—those that haven't spread to the lymph nodes—or ER-negative have been thought to have more favorable outcomes, Life ABC's website notes.

Ongoing Risk of Recurrence

Estrogen-negative breast cancer may not be as low-risk as once believed.

Most studies of breast cancer recurrence have looked at women for just five years after treatment, says Life ABC, but a substantial number of breast cancer recurrences happen six to 12 years after treatment. Some such recurrences are experienced by women thought to have been at low risk.

Although tamoxifen reduces breast cancer recurrence risk within five years of treatment, after five years breast cancer recurrence occurs at similar rates in both high-risk and low-risk women, reports Life ABC, and using tamoxifen longer than five years increases the risk of serious side effects without reducing the risk of breast cancer. Tamoxifen can increase the risk of developing uterine cancer and blood clots, says the National Cancer Institute.

HRT and Breast Cancer Recurrence

Two studies of HRT were abandoned because of breast cancer recurrence.

Hormone Replacement Therapy involves the use of estrogen and progesterone to treat menopausal symptoms. From 1997 to 1999, Swedish researchers looked at the effects of HRT on women who had survived breast cancer. The researchers intended to follow the women for five years, but they were forced to abort the study after just two years because of the high rate of breast cancer recurrence. Twenty-six of the 434 women had breast cancer recurrence after receiving hormonal treatments, a three-fold increased risk overall, reports the National Cancer Institute.The Women's Health Initiative, a long-term study that also looked at HRT, was abandoned in 2002 after estrogen and progestin therapy were found to increase the risk of breast cancer and heart disease says NCI.

Tamoxifen and Estrogen Levels

Breast cancer recurrence has been linked to high estrogen levels.

A study published in the March 2008 issue of "Cancer Epidemiology, Biomarkers & Prevention" reported that in cases of breast cancer recurrence, high levels of circulating estrogen were found, regardless of whether the women had undergone estrogen-blocking treatments for their cancer. Those with recurrence had twice as much estrogen in their blood as women who remained cancer-free, the researchers reported.

Estrogen causes breast cancer cells to divide and multiply, according to Dr. Jennifer Wu of Manhattan's Lenox Hill Hospital in New York City, but the study results don't mean that tamoxifen or aromatase inhibitors are not useful: The results justify their use, she says, but shows that dosages may need to be varied depending upon weight and other factors.

Estrogen and Fat

Fat tissue and excessive weight are linked with high estrogen levels.

Professor Cheryl Rock of the University of California led the estrogen-level study. Fat tissue produces estrogen, and Rock believes that diet and exercise may help to lower estrogen levels, reducing the risk of breast cancer recurrence.

"When people are overweight," Rock said, insulin levels suppress a protein that helps estrogen to work better.

Another study, conducted by Rowan T. Chlebowski and his colleagues at UCLA in 2005, found that a low-fat diet may reduce the risk of breast cancer recurrence. The largest benefit, however, was seen in women with ER-negative tumors. The risk of recurrence was lowered by 42 percent in these women while women who had suffered from ER-positive tumors saw little risk reduction. Chlebowski said factors other than the estrogen-cancer association must play a role in breast cancer recurrence.

The Changing Messages About Soy

Soybean may actually lower estrogen levels.

Women with breast cancer were once told to avoid soy foods, such as edamame, soy milk and tofu because it was believed that the isoflavones in soy mimicked estrogen in the body and could stimulate the growth of breast cancer cells.

Registered dietician Sally Scroggs says, "We have gone from saying, 'No soy for breast cancer survivors' to, 'It's not going to hurt,' to 'It may help.'"

The National Cancer Institute and the U.S. Department of Defense funded a study of 5,000 Chinese women who had received mastectomies. They found that the women who ate the most soy protein over four years had a 29 percent lowered risk of death due to cancer and a 32 percent decreased risk of breast cancer recurrence. They concluded that 9.5 to 11 grams of soy protein a day contributed to the decrease in risk.

Soy may actually compete with estrogen receptors and reduce both the ability of estrogen to stimulate breast cancer cells and the production of estrogen overall, the researchers theorized. The scientists said that the calcium, fiber, folate and protein in soy may contribute to decreased risk of breast cancer recurrence.

Scroggs says that when people eat more soy protein, they're likely eating smaller amounts of other foods such as red meat.

References

• Life ABC: Risk of Recurrence in Early Breast Cancer
• National Cancer Institute: Hormone Replacement Therapy and Breast Cancer Relapse
• HealthDay: Estrogen Levels in Blood Predict Breast Cancer's Return; Amanda Gardner
• American Cancer Society: Low-Fat Diet May Stall Breast Cancer Recurrence
• CNN: Soy May Benefit Breast Cancer Survivors, Study Says; Denise Mann

Resources

• Medical News Today: Estrogen Levels May Determine Breast Cancer Recurrence; Christian Nordqvist