Data published in Breast Cancer Research and Treatment from the University of Michigan health system revealed nearly 25 percent of women fail to adhere to recommended breast cancer treatment.
The study, led by University of Michigan Comprehensive Cancer Center researchers, affirmed one-quarter of women who are advised to take hormone-blocking therapies – daily doses of tamoxifen or aromatase inhibitors as part of a five year course of endocrine therapy – either fail to start or fail to complete the regimen.
Research has shown a consistent, prolonged course of endocrine-therapeutic drugs, for women whose breast cancer expresses for the hormones estrogen or progesterone, can reduce cancer recurrence and increase survival. Additional studies suggest using the drugs over a 10 year span may have extra breast cancer-inhibiting benefits.
Nearly two out of every three breast cancers test positive for hormone receptors.
Approximately 75 percent of breast tumors rely on estrogen, or are “estrogen dependent.” A cancer is called estrogen-receptor-positive (ER+ or ER-positive) if it has receptors for estrogen. This suggests that the cancer cells, like normal breast cells, may receive signals from estrogen that could promote growth.
A breast tumor biopsy, using a technique known as immunehistochemical staining, can detect the presence of estrogen receptors – a distinctive protein inside cells.
A cancer is progesterone-receptor-positive (PR+ or PR-positive) if it has progesterone receptors. Again, this means that the cancer cells may receive signals from progesterone that could promote their growth.
The goal of anti-hormonal treatment is to disable the cancer’s ability to code by deactivating the receptor sites.
Two different types of anti-hormone therapies are used to treat women with ER-positive breast tumors: selective estrogen receptor modulators (SERMs) and aromatase inhibitors. Tamoxifen is an example of a selective estrogen receptor modulator.
The drug competes with estrogen for binding sites on the estrogen receptor, proteins found inside cells, interfering with the signaling of estrogen. If activated by estrogen, the receptor is able to translocate into the nucleus, bind to DNA, and regulate the activity of different genes.
Aromatase inhibitors, which include drugs such as anastrozole, interfere with the body’s ability to make estrogen. They do so by blocking the activity of aromatase, an enzyme needed for the final steps of estrogen production.
Anastrozole also reduces the proliferation of progesterone. This drug is primarily used by postmenopausal women as it do not work as efficiently in premenopausal women. The ovaries make too much aromatase.
Anti-hormone therapies such as tamoxifen and anastrozole can be used to treat most stages of breast cancer. Women with early-stage breast cancer are usually treated with surgery followed by anti-hormone therapy, radiation therapy, and chemotherapy.
The study surveyed women about nine months after diagnosis and again four years later. The subjects were from Detroit and Los Angeles. The data was reported to Surveillance, Epidemiology and End Results, or SEER, tumor registries. They were questioned about their use of anti-hormonal therapy drugs.
Despite the documented benefits of anti-hormonal therapies on hormone-dependent breast cancers, the study found 11 percent of the 743 women reviewed never began treatment and 15 percent abandoned the therapy.
The primary reason many patients never start or discontinue the use of the medications is because of the side effects.
The concomitant effects of taking the medications mimics menopause-like symptoms which include hot flashes, vaginal dryness, and the drugs can cause uncomfortable joint pains. Serious side effects include blood clots and cataracts.
Researchers found women who received little information and guidance about endocrine therapy were less likely to begin the treatment. Women, who consulted with a breast surgeon as their primary follow-up, rather than an oncologist, were also less likely to begin endocrine therapy.
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