For more than 20 years, the drug tamoxifen has been used to treat patients with advanced breast cancer and as adjuvant therapy following surgery or radiation therapy to treat early-stage breast cancer.
In spite of the obvious benefits of tamoxifen, there are a number of side effects that have been attributed to the drug, and these range from mild to life-threatening. Some of the less serious side effects include an increased risk of hot flashes, night sweats, and vaginal discharge. New research presented at the recent Adjuvant Therapy for Breast Cancer NIH Consensus Development Conference shows that although some symptoms do appear to occur at a higher rate in patients taking tamoxifen, other side effects attributed to tamoxifen may not be the fault of the drug at all.
"What is important to realize is that many of the symptoms attributed to tamoxifen are menopause- and age-related changes," said Patricia A. Ganz, M.D., a professor at the UCLA Schools of Medicine and Public Health and the Jonsson Comprehensive Cancer Center. "Chemotherapy often precedes tamoxifen with precipitation of early menopause," she said. It naturally follows, she added, that a woman who takes tamoxifen after a diagnosis of breast cancer would attribute side effects to the drug shes taking rather than naturally occurring events.
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During the course of the trial, participants were asked to evaluate a range of symptoms including toxicity and anxiety and overall quality of life. Trial researchers found that women on tamoxifen experienced an increase in hot flashes. Specifically, 67% of women on tamoxifen reported an increase in hot flashes versus 45% of women on placebo.
Symptoms such as vaginal discharge, irritation, or bleeding were also reported more frequently in tamoxifen users. However, reported symptoms were generally mild.
Differences could not be found between the groups regarding symptoms such as racing heart, bone pain, joint pain, gastrointestinal distress, nausea, vomiting, sweaty hands, difficulty sleeping, irritability, depression, or fatigue. In terms of quality of life, patients reported that tamoxifen did not appear to have an adverse effect.
Two other studies cited by Ganz reported similar results. The NSABP B-14 Tamoxifen Trial, a trial focusing on node-negative, estrogen-receptorpositive (ER+) pre- and postmenopausal women, once again found an increase in the frequency of hot flashes and vaginal discharge among tamoxifen users. A recent cross-sectional study conducted by Ganz and other colleagues also found similar results. Neither study found differences in reports of weight gain, weight loss, or quality of life.
Sexual functioning, another area supposedly affected by tamoxifen, was also studied. Recent studies of breast cancer survivors found no statistically significant differences in sexual health and functioning. In the Breast Cancer Prevention Trial, rates of sexual activity did not differ between the tamoxifen and placebo groups.
Ganz also says that vaginal dryness, a cause of decreased sexual functioning, is not a specific side effect of tamoxifen but rather the probable result of age-related estrogen deficiency and even chemotherapy.
"Weight gain, decreased sexual interest, and vaginal dryness are commonly associated with aging in healthy women," said Ganz.
While most side effects attributed to tamoxifen may cause discomfort, there are those that can produce life-threatening conditions. Research has shown that tamoxifen can contribute to an increased incidence of endometrial cancer, stroke, blood clots, and cataracts. However, Ganz and other experts have repeatedly reported these occurrences as rare.
"The risks of endometrial cancer and blood clots are relatively small," said Joseph P. Costantino, Dr.P.H., a colleague of Ganz, an associate professor of biostatistics at the University of Pittsburgh Graduate School of Public Health, and an author on several of the papers published about the BCPT. "The magnitude of potential harm from endometrial cancer and blood clots increases with age, particularly after age 65."
"There are limited risks for endometrial cancer, stroke, and thromboembolic events in women under 50," said Ganz. "In most women with breast cancer, the potential survival gains from tamoxifen adjuvant therapy will offset the increased mortality risk for endometrial cancer."
In the final analysis, most experts agree that using tamoxifen as an adjuvant therapy is a decision to be taken after consideration of the benefits and risks.
"The challenge to physicians is to understand fully the side effects, risks, and benefits of tamoxifen adjuvant therapy and to communicate the information effectively to the patient. . . . Further, its critical to respect the patients personal perspective and choices if they dont feel the benefits outweigh the risks."
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