Tamoxifen adjuvant therapy is the strongest breast cancer chemopreventive agent. It is used for pre or postmenopausal women with large tumors expressing estrogen receptors whose nodes are positive or negative along with poor prognostic features. According to a study conducted by C.B.Fisher et al.,the use of selective estrogen receptor modifiers (SERM) such as tamoxifen and raloxifene has been shown to reduce the risk of new breast cancers by as much as 50%. SERM chemoprophylaxis are only considered for prevention of breast cancer in women who have at least a 1.7% of absolute risk of getting breast cancer over the subsequent five (5) years period. Tamoxifen (20 mg. orally per day for as long as 5 years) when compared to placebo,decreases the incidence of breast cancer in women who are at elevated risk for the disease. However, toxicities of these therapies can be life threatening for it increases the risk of endometrial cancer and thromboembolic diseases such as stroke and pulmonary embolism.
Clinical researchers (MH. Gail et al.) in the largest trial of tamoxifen for breast cancer published a paper estimating the risks and benefits of tamoxifen among women in different levels of risk for breast cancer. Studies revealed that “raloxifene” (SERM) also decreases the risk of breast cancer. Currently, tamoxifen is now being compared directly with raloxifene in a clinical trial of postmenopausal women. It can be noted that raloxifene is specifically approved for treatment of osteoporosis. Now, osteoporosis is a critical concern among postmenopausal women. A healthy lifestyle habits such as regular exercise and cessation of smoking along with ingestion of 1 g/calcium/day are recommended for all patients. Adjuvant use of tamoxifen reduces the risk of osteoporosis by its estrogenic agonistic effect in bone. Both tamoxifen and raloxifene have antiestrogenic effects in breast an central nervous system while they have estrogenic effects in bone and liver. But only tamoxifen has estrogenic effects in the endometrium. However, raloxifene should not be substituted for tamoxifen This is due to the fact that no data exists considering raloxifene as adjuvant therapy for breast cancer. Also, both tamoxifen and raloxifene should not be used together. And for both premenopausal and postmenopausal women,tamoxifen has become the standard of care.
Breast cancer will recur in about half of patients with localized disease. It was demonstrated that five (5) years of tamoxifen therapy reduces the recurrence by 40%. Median survival rate is about16 months with conventional treatment; tamoxifen for estrogen receptor positive tumors and combination chemotherapy for receptor negative tumors.
Risk is estimated by a model developed by Gail and colleagues and is available online at: http://bcra.nci.nih.gov/
A pesronal digital assistant (PDA) version of this helpful calculator is also available on the URL: http://www.palmgear.com/software/showsoftware.cfm?prodID=29820.
Finally,a list of ongoing cancer prevention trials can be found at the website of the National Cancer Institute: http://www.cancer.gov/clinical_trials/.