Many women receive the drugs Study Suggests Side Effects Can Help Determine Whether Breast Cancer Drug is Working (dateline December 30, 2008) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Study Suggests Side Effects Can Help Determine Whether Breast Cancer Drug is Working (dateline December 30, 2008)

Many women receive the drugs tamoxifen or anastrozole (brand name, Arimidex) as part of their breast cancer treatment. Now, a new study finds that women who experience side effects from the drug may have an indication that the drugs are working. The study found that women who took tamoxifen or anastrozole suffered side effects such as hot flashes, night sweats, and painful joints were 10 percent less likely to have a recurrence of breast cancer than women who did not have the symptoms.

Tamoxifen and anastrozole are both drugs used to treat breast cancer that is dependent on estrogen for survival (called estrogen-receptor positive breast cancer). Tamoxifen is used to treat both early and advanced forms of breast cancer. Clinical trials are under way to determine if anastrozole is appropriate for women with early stage breast cancer.

In analyzing over 9,000 patient records, the researchers found that hot flashes, night sweats and painful joints could be used to predict how effective a breast cancer patient's drug treatment could be. Women who reported any of these symptoms within three months of starting treatment with tamoxifen or anastrozole were less likely to have a recurrence of breast cancer, compared to women who did not experience them," said Dr. Jack Cuzick of Cancer Research UK in a charity news release.

The researchers performed their study using data from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) clinical trial. The ATAC clinical trial was one of the largest breast cancer treatment studies in post-menopausal women with early breast cancer. This clinical trial compared treatment with anastrozole to treatment with tamoxifen, either alone or in combination. Results from the trial showed no significant difference among women who received tamoxifen alone compared to those who received a combination of anastrozole and tamoxifen, which suggests that tamoxifen should not be given in combination with anastrozole.

While the results of the study are intriguing, the researchers caution that it is too early to conclude that experiencing side effects can mean that the drugs are more effective. "At the moment all we can say is that the symptoms indicate the likely success of the treatment," said Dr. Cuzick. However, he noted that the treatment is designed to starve potential cancers of estrogen, and therefore experiencing symptoms such as hot flashes could mean that there are lower levels of estrogen in the body.

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