Tamoxifen is used in three situations. In metastatic cancer (the cancer has already spread) if the patients tumor was hormone sensitive (positive estrogen/progesterone receptors) than this drug will be effective (get a response that lasts months) in about 60% of the women, Once the cancer becomes resistant to tamoxifen, then other drugs in the hormone therapy class ( anti-estrogens which also include:Arimidex (anastrozole), Fareston (toremifene citrate), Femara (letrozole) and other hormones like Megace (megestrol acetate) Cytadren or Halotestin) will be tried unless life threatening metastases are present.In the adjuvant setting (i.e. after initial surgery or radiation, designed to decrease the risk of a relapse) Tamoxifen will lower the risk of a relapse by about 30%, and as a preventative (i.e. women at risk for getting cancer) it will lower the risk of developing breast cancer by about 40 - 50%.

The role of tamoxifen in the treatment and prevention of breast cancer.

Jordan VC

Department of Human Oncology, University of Wisconsin

Tamoxifen is a nonsteroidal antiestrogen that has found successful applications for each stage of breast cancer in the treatment of selected patients. Tamoxifen was originally introduced for the treatment of advanced disease in postmenopausal women; however, the drug is now also available for the palliative treatment of premenopausal women with estrogen receptor (ER) positive disease. The proven efficacy of tamoxifen and the low incidence of side effects made the drug an ideal agent to test as an adjuvant therapy for women with node-positive breast cancer. Laboratory studies indicate that long-term treatment schedules may provide maximal benefit in preventing recurrence, and recent analysis of clinical trials demonstrates that between 2 and 5 years of adjuvant tamoxifen therapy provides a survival advantage for postmenopausal women with node-positive disease. Similarly, adjuvant studies in node-negative breast cancer have demonstrated an increase in the disease-free survival of both pre- and postmenopausal patients with ER-positive tumors. However, the extended use of tamoxifen has raised questions about the long-term safety of antiestrogen therapy. Initial concerns that the long-term administration of an antiestrogen would increase bone loss and increase the risks of coronary heart disease appear to be unwarranted. Tamoxifen has some estrogen-like activities in postmenopausal women and causes a preservation of bone in the lumbar spine and a decrease in circulating cholesterol. Indeed, a reduction in fatal myocardial infarction (MI) has been noted during 5 years of tamoxifen therapy, possibly the direct result of a prolonged reduction in circulating cholesterol. However, the estrogen-like qualities of tamoxifen that could be valuable as a hormone replacement therapy for all postmenopausal women following a diagnosis of breast cancer may also increase the risk for developing endometrial carcinoma.

Drug Saf 1993 May;8(5):381-97

A risk-benefit assessment of tamoxifen therapy.

Catherino WH, Jordan VC

Department of Human Oncology, University of Wisconsin Comprehensive Cancer Center, Madison.

Tamoxifen is the endocrine treatment of choice for all women with hormonally responsive breast cancer. 30 years of experience in both the laboratory and clinical setting have shown tamoxifen to be an effective adjuvant treatment with minor short term adverse effects. However, as therapeutic use has extended to 5 years and beyond, and as clinical trials begin which will assess the effectiveness of tamoxifen as a preventive treatment, concern about possible long term adverse effects is justified. Tamoxifen has an estrogen-like influence on the skeletal and cardiovascular systems, resulting in decreases in both postmenopausal bone loss and low density lipoprotein (LDL) levels. These effects will, it is hoped, result in decreases in the incidences of osteoporosis and coronary heart disease, which are major causes of morbidity and mortality in the postmenopausal age group. Tamoxifen therapy also results in decreased rates of contralateral breast cancer. Long term tamoxifen treatment may result in a small increase in the incidence of endometrial and/or hepatocellular carcinoma, but with millions of women taking tamoxifen for long periods, such small increases in incidence translate to a significant number of women at risk. Tamoxifen is clearly beneficial for short term treatment, but the clinical decision of tamoxifen use in the long term must be made on the individual benefits versus risks of tamoxifen treatment.

Oncology (Huntingt) 1997 Feb;11(2 Suppl 1):21-3

Risks and benefits of tamoxifen therapy.

Assikis VJ, Jordan VC

Research Program, Robert H. Lurie Cancer Center, Northwestern University, Medical School, Chicago, USA.

Tamoxifen is the most widely prescribed endocrine therapy for breast cancer, with more than 7.5 million woman-years of clinical experience. Tamoxifen has both antiestrogenic and estrogenic activity. The antiestrogenic activity accounts for its efficacy against breast cancer, while the estrogenic activity is considered to be associated with positive effects on bone mineral density and lipid profiles and a proliferative effect on the endometrium in some women. Tamoxifen has a good tolerability profile and has demonstrated benefits for breast cancer patients in prolonging overall and disease-free survival and reducing the incidence of contralateral breast cancer. These known benefits of tamoxifen far outweigh the risk of endometrial cancer in tamoxifen-treated patients with breast cancer.

Clin Cancer Res 1998 Mar;4(3):527-34

Update on endocrine therapy for breast cancer.

Buzdar AU, Hortobagyi G

The University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.

The choice of endocrine agent for breast cancer depends on the menopausal status of the patient, the stage of disease, prognostic factors, and the toxicity profile of the agent. Endocrine therapies are typically given sequentially, with the least toxic therapy given first. Tamoxifen is considered first-line endocrine therapy for all stages of breast cancer. New antiestrogens in development include nonsteroidal agents related to tamoxifen and pure steroidal antiestrogens. Luteinizing hormone-releasing hormone agonists are an effective form of endocrine therapy for premenopausal women with advanced breast cancer, and aromatase inhibitors are effective in postmenopausal women. Newer and more selective aromatase inhibitors that are p.o. active and have improved side-effect profiles have been developed. Recent trials have found these agents to improve survival in comparison to the progestins; thus, aromatase inhibitors are replacing progestins as second-line therapy for metastatic disease. Current trials are examining the potential role of aromatase inhibitors as first-line therapy for metastatic disease or as adjuvant therapy for early disease. The antiprogestins and antiandrogens studied thus far have had only limited success in breast cancer clinical trials.

Semin Oncol 1996 Aug;23(4 Suppl 9):2-9

Hormonal approaches to breast cancer treatment and prevention: an overview.

Vogel CL

Mt Sinai Comprehensive Breast Center, Miami Beach, FL 33140, USA.

Hormonal agents play a critical role in the palliation of advanced breast cancer, as well as adjuvant therapy to surgery and radiation in patients with primary breast cancer. Tamoxifen appears to be the therapy of choice for the initial treatment of metastatic breast cancer in both premenopausal and postmenopausal women, although some clinicians prefer oophorectomy or the use of luteinizing hormone releasing hormone analogues in premenopausal patients. Historically, second-line hormonal therapy for metastatic disease has been with a progestin; however, due to the troubling side effects of weight gain and dyspnea, progestins may soon be replaced by aromatase inhibitors. The development of new antiestrogens lacking estrogen-agonist activity for metastatic disease is in its earliest clinical developmental phases. For adjuvant therapy in postmenopausal women, there is conflicting evidence as to whether the combination of a hormonal agent (ie, tamoxifen) plus chemotherapy provides an advantage over hormonal therapy alone. In premenopausal women areas of active investigation include combination hormonal therapy (eg, tamoxifen plus luteinizing hormone releasing hormone analogues or oophorectomy) and combination chemohormonal therapy (concomitant v sequential). Tamoxifen had been associated with rare cases of thromboembolic events and secondary endometrial cancers. The etiology of these secondary cancers is unclear and controversial; however, the benefits of tamoxifen far outweigh the risks for both palliative and surgical adjuvant therapy. The success of tamoxifen in preventing cancer recurrence in the contralateral breast has led to clinical investigation of the drug for the chemoprevention of breast cancer in women at high risk for development of the disease.

Invest New Drugs 1999;17(3):285-311

Antiestrogens--tamoxifen, SERMs and beyond.

Dhingra K

Hoffman-La Roche Inc.

The cellular effects of estrogens are mediated by binding to nuclear receptors (ER) which activate transcription of genes involved in cellular growth control.  Estrogens are also a causative factor in the pathogenesis of a variety of neoplastic and non-neoplastic diseases, including breast cancer, endometrial cancer, endometriosis, and uterine fibroids, among others. Antiestrogens, such as tamoxifen, are widely used for the treatment of breast cancer. Tamoxifen produces objective tumor shrinkage in advanced breast cancer, reduces the risk of relapse in women treated for invasive breast cancer, and prevents breast cancer in high-risk women. Although, initially developed as an antiestrogen, tamoxifen can also prevent postmenopausal osteoporosis as well as reduce cholesterol, due to its estrogen-agonist effects. Its estrogen-agonist activity, however, can lead to significant side-effects such as endometrial cancer and thromboembolic phenomena. This has led to the concept of "ideal" selective estrogen receptor modulators (SERMs), drugs that would have the desired, tissue selective, estrogen-agonist or -antagonist effects. Raloxifene is a SERM which has the desirable mixed agonist/antagonist effects of tamoxifen but does not cause uterine stimulation. "Pure" antiestrogens may provide very potent estrogen-antagonist drugs, but are likely to be devoid of beneficial effects on bone and lipids. Future drug development efforts should focus on developing superior SERMs that have a greater efficacy against ER-positive tumors and do not cause hot flashes or thromboembolism, and explore combination strategies to simultaneously target hormone-dependent as well as hormone-independent breast cancer.

Drugs 1999 May;57(5):653-63

Selective estrogen receptor modulators: a look ahead.

Mitlak BH, Cohen FJ

Indiana University School of Medicine

Selective estrogen receptor modulators (SERMs) are structurally diverse compounds that bind to estrogen receptors (ER) and elicit agonist or antagonist responses depending on the target tissue and hormonal milieu. Several SERMs are marketed or are in clinical development, including triphenylethylenes (tamoxifen and its derivatives: toremifene, droloxifene and idoxifene), chromans (levormeloxifene), benzothiophenes (raloxifene, LY353381) and naphthalenes (CP336,156). Tamoxifen and toremifene, both used to treat advanced breast cancer, also have beneficial effects on bone mineral density and serum lipids in postmenopausal women. Tamoxifen was recently shown to decrease the risk of invasive breast cancer in women at high risk. Unfortunately, both drugs also have stimulatory effects on the endometrium. Raloxifene, used for prevention of postmenopausal osteoporosis and fragility fractures, also has favourable effects on bone mineral density, serum lipids and the incidence of invasive breast cancer in postmenopausal women but does not stimulate the endometrium. Like replacement estrogens, SERMs increase the risk of venous thromboembolism. SERMs offer post-menopausal women many of the advantages of estrogen replacement while mitigating some of the disadvantages, particularly the concern over breast cancer. Newer SERMs, exemplified by raloxifene, also eliminate the concerns over endometrial stimulation that were not addressed by first generation SERMs.

Clinical Studies--Adjuvant Breast Cancer

Among women with ER positive or unknown breast cancer and positive nodes who received about 5 years of treatment, overall survival at 10 years was 61.4% for NOLVADEX vs. 50.5% for control. The recurrence free rate at 10 years was 59.7% for NOLVADEX vs. 44.5% for control.. Among women with ER positive or unknown breast cancer and negative nodes who received about 5 years of treatment, overall survival at 10 years was 78.9% for NOLVADEX vs. 73.3% for control. The recurrence free rate at 10 years was 79.2% for NOLVADEX versus 64.3% for control.

The effect of the scheduled duration of tamoxifen may be described as follows. In women with ER positive or unknown breast cancer receiving 1 year or less, 2 years or about 5 years of NOLVADEX, the proportional reductions in mortality were 12%, 17% and 26%, respectively (trend significant at 2p < 0.003). The corresponding reductions in breast cancer recurrence were 21%, 29% and 47% (trend significant at 2p < 0.00001).

Benefit is less clear for women with ER poor breast cancer in whom the proportional reduction in recurrence was 10% (2p = 0.007) for all durations taken together, or 9% (2p = 0.02) if contralateral breast cancers are excluded. The corresponding reduction in mortality was 6% (NS). The effects of about 5 years of NOLVADEX on recurrence and mortality were similar regardless of age and concurrent chemotherapy. There was no indication that doses greater than 20 mg per day were more effective.

Contralateral Breast Cancer --The incidence of contralateral breast cancer is reduced in breast cancer patients (premenopausal and postmenopausal) receiving NOLVADEX compared to placebo. In clinical trials with NOLVADEX of 1 year or less, 2 years, and about 5 years duration, the proportional reductions in the incidence rate of contralateral breast cancer among women receiving NOLVADEX were 13% (NS), 26% (2p = 0.004) and 47% (2p < 0.00001), with a significant trend favoring longer tamoxifen duration (2p = 0.008). The proportional reduction in the incidence of contralateral breast cancer were independent of age and ER status of the primary tumor. Treatment with about 5 years of NOLVADEX reduced the annual incidence rate of contralateral breast cancer from 7.6 per 1000 patients in the control group compared with 3.9 per 1000 patients in the tamoxifen group.

In a large randomized trial in Sweden (the Stockholm Trial) of adjuvant NOLVADEX 40 mg/day for 2-5 years, the incidence of second primary breast tumors was reduced 40% (p < 0.008) on tamoxifen compared to control. In the NSABP B-14 trial in which patients were randomized to NOLVADEX 20 mg/day for 5 years vs. placebo, the incidence of second primary breast cancers was also significantly reduced (p < 0.01). In NSABP B-14, the annual rate of contralateral breast cancer was 8.0 per 1,000 patients in the placebo group compared with 5.0 per 1,000 patients in the tamoxifen group, at 10 years after first randomization.

Clinical Studies--Reduction in Breast Cancer Incidence in High Risk Women

After a median follow-up of 4.2 years, the incidence of invasive breast cancer was reduced by 44% among women assigned to NOLVADEX (86 cases-NOLVADEX, 156 cases-placebo; p<0.00001; relative risk (RR)=0.56, 95% CI: 0.43-0.72). A reduction in the incidence of breast cancer was seen in each prospectively specified age group (</=49, 50-59, >/=60), in women with or without LCIS, and in each of the absolute risk levels specified in Table 2. A non-significant decrease in the incidence of ductal carcinoma in situ (DCIS) was seen (23-NOLVADEX, 35-placebo; RR=0.66; 95% CI: 0.39-1.11).

There was no statistically significant difference in the number of myocardial infarctions, severe angina, or acute ischemic cardiac events between the two groups (61-NOLVADEX, 59-placebo; RR=1.04, 95% CI: 0.73-1.49).

No overall difference in mortality (53 deaths in NOLVADEX group vs. 65 deaths in placebo group) was present. No difference in breast cancer-related mortality was observed (4 deaths in NOLVADEX group versus 5 deaths in placebo group).

Although there was a non-significant reduction in the number of hip fractures (9 on NOLVADEX, 20 on placebo) in the NOLVADEX group, the number of wrist fractures was similar in the two treatment groups (69 on NOLVADEX, 74 on placebo). No information regarding bone mineral density or other markers of osteoporosis is available.

The risks of NOLVADEX therapy include endometrial cancer, DVT, PE, stroke, cataract formation and cataract surgery (See Table 2). In the NSABP P-1 trial, 33 cases of endometrial cancer were observed in the NOLVADEX group vs. 14 in the placebo group (RR=2.48, 95% CI: 1.27-4.92). Deep vein thrombosis was observed in 30 women receiving NOLVADEX vs. 19 in women receiving placebo (RR=1.59, 95% CI: 0.86-2.98). Eighteen cases of pulmonary embolism were observed in the NOLVADEX group vs. 6 in the placebo group (RR=3.01, 95% CI: 1.15-9.27). There were 34 strokes on the NOLVADEX arm and 24 on the placebo arm (RR=1.42; 95% CI: 0.82-2.51). Cataract formation in women without cataracts at baseline was observed in 540 women taking NOLVADEX vs. 483 women receiving placebo (RR=1.13, 95% CI: 1.00-1.28). Cataract surgery (with or without cataracts at baseline) was performed in 201 women taking NOLVADEX vs. 129 women receiving placebo (RR=1.51, 95% CI 1.21-1.89)