Risk/benefit assessment of tamoxifen to prevent breast cancer-still a work in progress?

Cultural Connections: the Key to Retention of Black, Latina, and Arab Women in the Kin Keeper(SM) Cancer Prevention Intervention Studies

Diverse racial and ethnic populations must be included in research studies in order to address health disparities. Retaining hard-to-reach populations including poor, underserved, and racial/ethnic groups in longitudinal studies can be quite difficult. Using innovative retention strategies that address culture and community are imperative. The objective of this report is to identify and describe strategies for successful retention rates among a unique group of hard-to-reach racial/ethnic participants. We analyzed the follow-up rates in two different cohorts using the Kin Keeper(SM) study design. The aim of Study A was to examine the capability of the Kin Keeper(SM) education to increase health literacy in breast and cervical cancer. The primary aim of Study B was to measure changes in breast and cervical cancer screening after receiving the Kin Keeper(SM) education. Retention rates were analyzed and compared over 12 months for both cohorts. We found good retention rates for both cohorts with each having a unique set of differences. The overall follow-up rate was 82 % for Study A and 88 % for Study B with demographic differences between the studies reported herein. Despite changing cultural, community, and geopolitical factors, we were able to maintain consistent participation for each study. We attribute high retention rates to trusted cultural connections and the flexibility to adjust retention strategies.

Chemoprevention activity of dipyridamole in the MMTV-PyMT transgenic mouse model of breast cancer

Dipyridamole (DPM) is widely used to prevent strokes and vascular thrombosis. Combination therapy of DPM and antimetabolites has shown synergistic anticancer activity. This study investigated the chemopreventive effects of DPM in the mouse mammary tumor virus promoter-driven polyoma middle T oncoprotein metastatic breast cancer model. We also investigated the effects of DPM on gene and miRNA expression. Chemopreventive activity was assessed by comparing the time to onset of palpable lesions, primary tumor growth kinetics, and the number of lung metastases in transgenic mice treated with DPM or vehicle. Gene expression and miRNA expression profiles of mammary tumor tissues were then analyzed using the Affymetrix GeneChip or miRNA 2.0 arrays. Real-time quantitative PCR was used to confirm changes in gene expression. Treatment with DPM beginning at the age of 4 weeks delayed the onset of palpable lesions, delayed tumor progression, and suppressed lung metastasis. Microarray gene expression analysis identified 253 genes differentially expressed between DPM-treated and control mammary tumors. miRNA expression analysis revealed that 53 miRNAs were altered by DPM treatment. The results indicate that DPM has chemoprevention activity against breast cancer tumorigenesis and metastasis in mice. The array analyses provide insights into potential mechanisms of DPM's chemopreventive effects, involving upregulation of several genes and miRNAs known to suppress cancer growth and/or metastasis and downregulation of genes known to promote cancer. Some of these genes have not been previously studied in breast cancer and may serve as novel molecular targets for breast cancer chemoprevention.

Recruitment strategy cost and impact on minority accrual to a breast cancer prevention trial

BACKGROUND

Recruitment of minorities to cancer prevention trials is difficult and costly. Early-phase cancer prevention trials have fewer resources to promote recruitment. Identifying cost-effective strategies that can replace or supplement traditional recruitment methods and improve minority accrual to small, early-phase cancer prevention trials are of critical importance.

PURPOSE

To compare the costs of accrual strategies used in a small breast cancer prevention trial and assess their impact on recruitment and minority accrual.

METHODS

A total of 1196 potential subjects with a known recruitment source contacted study coordinators about the SOY study, a breast cancer prevention trial. Recruitment strategies for this study included recruitment from within the Northwestern University network (internal strategy), advertisements placed on public transportation (Chicago Transit Authority (CTA)), health-related events, media (print/radio/television), and direct mail. Total recruitment strategy cost included the cost of study personnel and material costs calculated from itemized receipts. Incremental cost-effectiveness ratios (ICERs) were calculated to compare the relative cost-effectiveness of each recruitment strategy. If a strategy was more costly and less effective than its comparator, then that strategy was considered dominated. Scenarios that were not dominated were compared. The primary effectiveness measure was the number of consents. Separate ICERs were calculated using the number of minority consents as the effectiveness measure.

RESULTS

The total cost of SOY study recruitment was US$164,585, which included the cost of materials (US$26,133) and personnel (US$138,452). The internal referral strategy was the largest source of trial contacts (748/1196; 63%), consents (107/150; 71%), and minority consents (17/34; 50%) and was the most expensive strategy (US$139,033). CTA ads generated the second largest number of trial contacts (326/1196; 27%), the most minority contacts (184/321; 57%), and 16 minority consents (16/34; 47%), at a total cost of US$15,562. The other three strategies yielded many fewer contacts and consents. The methods of health events, CTA ads, and the internal strategy showed some evidence of cost-effectiveness (ICER: US$581, US$717, and US$1524, respectively). The CTA strategy was the most cost-effective strategy for minority accrual (ICER: US$908).

LIMITATIONS

Recall bias may have limited the accuracy of estimated time spent on recruitment by study personnel. Also, costs spent specifically on minority accrual were unobtainable; results may not be generalizable to other settings; and cost-effectiveness data for the methods of media, health events, and direct mail should be interpreted with caution since these methods generated few consents.

CONCLUSIONS

Public transportation ads have the potential to generate numerous minority contacts and consents at a reasonable cost within an urban setting. Combined with traditional methods of recruitment, this method can lead to timelier study completion and increased minority accrual. Future research should prospectively track recruitment and costs in order to better assess the cost-effectiveness of recruitment methods used to target minority populations.

Tamoxifen for the prevention of breast cancer: current status of the National Surgical Adjuvant Breast and Bowel Project P-1 study

BACKGROUND

Initial findings from the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial (P-1) demonstrated that tamoxifen reduced the risk of estrogen receptor-positive tumors and osteoporotic fractures in women at increased risk for breast cancer. Side effects of varying clinical significance were observed. The trial was unblinded because of the positive results, and follow-up continued. This report updates our initial findings.

METHODS

Women (n = 13,388) were randomly assigned to receive placebo or tamoxifen for 5 years. Rates of breast cancer and other events were compared by the use of risk ratios (RRs) and 95% confidence intervals (CIs). Estimates of the net benefit from 5 years of tamoxifen therapy were compared by age, race, and categories of predicted breast cancer risk. Statistical tests were two-sided.

RESULTS

After 7 years of follow-up, the cumulative rate of invasive breast cancer was reduced from 42.5 per 1000 women in the placebo group to 24.8 per 1000 women in the tamoxifen group (RR = 0.57, 95% CI = 0.46 to 0.70) and the cumulative rate of noninvasive breast cancer was reduced from 15.8 per 1000 women in the placebo group to 10.2 per 1000 women in the tamoxifen group (RR = 0.63, 95% CI = 0.45 to 0.89). These reductions were similar to those seen in the initial report. Tamoxifen led to a 32% reduction in osteoporotic fractures (RR = 0.68, 95% CI = 0.51 to 0.92). Relative risks of stroke, deep-vein thrombosis, and cataracts (which increased with tamoxifen) and of ischemic heart disease and death (which were not changed with tamoxifen) were also similar to those initially reported. Risks of pulmonary embolism were approximately 11% lower than in the original report, and risks of endometrial cancer were about 29% higher, but these differences were not statistically significant. The net benefit achieved with tamoxifen varied according to age, race, and level of breast cancer risk.

CONCLUSIONS

Despite the potential bias caused by the unblinding of the P-1 trial, the magnitudes of all beneficial and undesirable treatment effects of tamoxifen were similar to those initially reported, with notable reductions in breast cancer and increased risks of thromboembolic events and endometrial cancer. Readily identifiable subsets of individuals comprising 2.5 million women could derive a net benefit from the drug.

Barriers to minority participation in breast carcinoma prevention trials

BACKGROUND

Breast carcinoma prevention trials must recruit large cohorts of women who have an above-average risk of developing breast carcinoma. Recruitment for the Study of Tamoxifen and Raloxifene (STAR) trial required volunteers to complete a risk assessment questionnaire form (RAF). Women whose estimated risk of developing breast carcinoma in the next 5 years was > or = 1.67% based on the Gail model were invited to participate in STAR. Less than 4% of participants in the previously conducted P1 (tamoxifen vs. placebo) trial were minority women. We, therefore, studied barriers to minority participation in STAR among black, white, and Hispanic women who completed an RAF.

METHODS

The authors analyzed the association of Gail model risk factors, education, and insurance with race/ethnicity using chi-square tests and two-sided P values. They developed logistic regression models of trial eligibility, controlling for the Gail model risk factors, education, and insurance status.

RESULTS

Among 823 women who completed an RAF, white women were 10 times as likely as Hispanic women and 45 times as likely as black women to be eligible for STAR. Age at first birth (P = 0.04), having an affected first-degree relative (P < 0.0001), having had a biopsy (P < 0.0001), education (P < 0.0001), and insurance status (P < 0.0001) varied by race/ethnicity. All variables except insurance status were associated with eligibility when race was excluded from the model. In a model that included race/ethnicity, the same factors remained statistically significant.

CONCLUSIONS

These findings suggested that both the race/ethnicity adjustment and socioeconomic factors were barriers to eligibility for and contribute to low minority participation in breast cancer prevention trials.

Estimates of the number of US women who could benefit from tamoxifen for breast cancer chemoprevention

BACKGROUND

The Breast Cancer Prevention Trial demonstrated that tamoxifen treatment produced a 49% reduction in the risk of invasive breast cancer among women at elevated risk for the disease. The U.S. Food and Drug Administration (FDA) subsequently approved tamoxifen for women aged 35 years or older with a 5-year breast cancer risk of 1.67% or higher for breast cancer chemoprevention. However, tamoxifen use has been associated with adverse outcomes, and not all eligible women have a positive benefit/risk ratio.

METHODS

We used weighted data from the year 2000 National Health Interview Survey Cancer Control Module to estimate the total number of U.S. women, aged 35-79 years, who were eligible for tamoxifen chemoprevention based on the FDA eligibility criteria. We also estimated the numbers of white and black women who would benefit from tamoxifen chemoprevention on the basis of a positive benefit/risk index developed by Gail et al.

RESULTS

Of the 65,826,074 women aged 35-79 years without reported breast cancer in the United States in 2000, 10,232 816 women (15.5%, 95% confidence interval [CI] = 14.7% to 16.3%) would be eligible for tamoxifen chemoprevention. The percentage of U.S. women who would be eligible varied dramatically by race, with 18.7% (95% CI = 17.8% to 19.7%) of white women, 5.7% (95% CI = 4.3% to 7.5%) of black women, and 2.9% (95% CI = 2.1% to 3.9%) of Hispanic women being eligible. Of the 50,104,829 white U.S. women aged 35-79 years, 2,431,911 (4.9%, 95% CI = 4.3% to 5.4%) would have a positive benefit/risk index for tamoxifen chemoprevention. Of the 7,481,779 black U.S. women aged 35-79 years, only 42,768 (0.6%, 95% CI = 0.2% to 1.3%) would have a positive benefit/risk index. Among white women, 28,492 (95% CI = 24,693 to 32,292) breast cancers would be prevented or deferred if those women who have a positive net benefit index took tamoxifen over the next 5 years.

CONCLUSION

A substantial percentage of U.S. women would be eligible for tamoxifen chemoprevention according to FDA criteria, but a much smaller percentage would have an estimated net benefit. Nevertheless, this latter percentage corresponds to more than two million women.

Tamoxifen for prevention of breast cancer

OBJECTIVE

To review data on the use of tamoxifen for primary prevention of breast cancer.

DATA SOURCES

A literature search was performed through MEDLINE (1992-May 2002) using the key words tamoxifen, breast cancer, and prevention.

DATA SYNTHESIS

Breast cancer is the most common malignancy detected in American women. Attempts to reduce morbidity and mortality include early detection programs and chemoprevention. Clinical trials of tamoxifen for reduction of breast cancer risk are reviewed.

CONCLUSIONS

Tamoxifen may reduce the risk of primary breast cancer in women at increased risk. The benefit of tamoxifen in women who are not at risk is uncertain. The risks of developing thromboembolic disorders or endometrial cancer must be considered before tamoxifen is prescribed. Women should be given all of the information about the benefits and risks of tamoxifen use so that they can make an informed decision based on the best data available.

Breast cancer risk assessment in patients seen in a gynecologic oncology clinic

The objective of this study was to determine if breast cancer risk assessment following the Gail model should be incorporated into a gynecologic oncology clinic. The Gail model was used to assess the risk of breast cancer in 329 patients with preinvasive lower genital tract disease (Pre, n = 86), invasive vulvar and cervical (Cx, n = 102), uterine (Ut, n = 87), and ovarian cancer (Ov, n = 54) seen in an inner city gynecologic oncology office. T-test, chi square test, and Pearson and Spearman correlation coefficients were used for statistical evaluation. A P-value of less than 0.05 was regarded significant. An estimated 5-year risk of breast cancer of 1.67 or more was noted in 9% of the Pre patients, 5% of Cx patients, 21% of the Ut patients, and 9% of the Ov patients. The difference between Cx and Ut patients was significant. The average 5-year risk was calculated at 0.77 for Pre patients, 0.77 for Cx patients, 1.18 for Ut patients, and 1.11 for Ov patients. These differences were significant, but mirror the age distribution. The average age was 43.6 for Pre patients, 52.2 years for Cx, 61.5 years for Ut, and 58.5 years for Ov patients; these differences were significant. When calculations were corrected for the mean age (53 years), there were no significant differences between groups regarding the average risk: Pre: 1.04, Cx: 0.81, Ut: 0.96, Ov: 0.97. Only eight patients (2.4%), six of them in the Pre and Cx group, would be expected to derive significant benefit from tamoxifen therapy. We conclude that elevated 5-year breast cancer risk to 1.67% or higher is noted in about 11% of patients seen in a gynecologic oncology office, mainly related to age and family history. Risk assessment and regular screening should be part of any follow-up exam.

[Approach of menopause in women at risk for breast cancer]

The small but significant increase in risk of discovering breast cancer in women with hormone replacement therapy and the recent discussion of coronary benefit of this treatment have led many authors to insist on the necessity to evaluate the benefit/risks ratio before administration. This evaluation is particularly important for women that are already at high risk of breast cancer because of some genetic predisposition, family history or some benign breast diseases. In these cases, it is important to evaluate the absolute risk of breast cancer, to define the patient's needs more precisely, to specify menopausal symptoms; it is also important to evaluate the risk of osteoporosis, to review the various therapeutic possibilities, which are not only estrogen/progestin treatments (there are alternative treatments), and to give the patients honest information. Before obtaining the results of current trials, we are proposing here a pragmatic attitude and a decision algorithm to adopt a therapeutic attitude more easily which will be decided together by both patients and their physicians.

SERMs, ethnicity, and clinical trials: opportunities and challenges

Selective estrogen receptor modulators (SERMs) are an exciting new class of pharmacotherapeutics that may have application in a wide variety of disease states. The science, both basic and clinical, that would guide the usage of these agents is in some respects at a relatively early developmental stage. Thus, the research community has an opportunity, before their use becomes widespread, to structure clinical trials such that the most complete profiles of benefits and risks are described. Tamoxifen is the SERM that has been most extensively studied and for which there are indications for both treatment and prevention of breast cancer based on trials involving more than 50,000 women. Despite this seemingly adequate sample size, an extremely important question remains unanswered--namely, whether there are ethnic differences in benefit and adverse effects of SERMs. It has generally been the case that new pharmacologic agents are tested in relatively small numbers of subjects, often only male, in North America and western Europe. While the populations are multi-ethnic, clinical trial subjects are most often not representative of the ethnic variability of these areas. Guidelines for usage of new drugs based on data from small, ethnically limited population groups are then generalized to other population groups, without consideration that differences in drug metabolism and/or responsiveness might exist.

Defining benefits and risks for SERMs in clinical trials and clinical practice

Differences between clinical trials and clinical practice with respect to defining benefits and benefit/risk ratios for SERMs are discussed. These differences stem from the perception that there is discordance between the statistical significance and the "clinical meaningfulness" of research data in the minds of the practitioner and patient. One way that we can obtain data that are more clinically meaningful is to solicit input in the planning stages of clinical trials from practicing community clinicians and their patients. However, there are drawbacks to community input, such as potentially unrealistic expectations. A further issue is the need to characterize clinically meaningful drug benefits and acceptable benefit/risk ratios for a drug. Individual patients have differences regarding their views of optimal benefits and acceptable risks, so a method or tool for determining what is clinically meaningful would be helpful in presenting comprehensive information to the patient. To present useful information to clinicians, head-to-head comparisons of a new drug with a standard agent should be undertaken. NIH's support in this area of comparator trials is critical to their implementation. Estrogen has been considered the standard for comparison of agents for conditions associated with menopause in clinical trials. Estrogen has been the "gold standard" in clinical practice as well. In fact, challenging the position of estrogen, even where scientifically supported, has proven to be an uphill battle. In the practice setting, we elaborate the challenges of keeping up with the scientific literature and of then communicating this information in a fashion that is relevant to the individual patient.

What would be the properties of an ideal SERM?

Selective estrogen receptor modulators (SERMs) are drugs that bind to the estrogen receptor (ER); in some tissues they act like estrogen (agonists), while in other tissues they oppose the action of estrogen (antagonists). The SERM tamoxifen acts as an estrogen antagonist in the breast in that it prevents and treats breast cancer, but it acts as an estrogen agonist in the endometrium, where it can induce cancer. Estrogen, and to a lesser extent SERMs, are effective in preventing and treating osteoporosis. Contrary to the prevalent hypothesis that estrogen provides benefit to women with regard to secondary prevention of coronary heart disease (CHD), randomized clinical trials have demonstrated that estrogen is associated with an increased risk of CHD in this population of women. Conflicting results have been reported on the effect of estrogens on cognitive function. The latest and largest randomized clinical trials have demonstrated a beneficial role in short-term memory in nondemented women, in contrast to the absence of such benefit in improving symptoms in women with Alzheimer's disease. Although estrogens have been used successfully to treat some menopausal symptoms such as hot flashes, the SERMs tamoxifen and raloxifene actually induce or increase hot flashes. Data on the beneficial and adverse effects of estrogen and SERMs are reported along with an elaboration of the constellation of properties that would characterize an ideal SERM working through the ER.

Chemoprevention for high-risk women: tamoxifen and beyond

The demonstration by the National Surgical Adjuvant Breast Project (NSABP) that 5 years of tamoxifen therapy is associated with an approximate 50% reduction in breast cancer incidence in high-risk women was a milestone in breast cancer prevention. Because tamoxifen is associated with increased risk of side-effects such as hot flashes, menstrual abnormalities, uterine cancer, and thromboembolic phenomena, its use will not be advisable or acceptable for all high-risk women. Women over 50 years of age appear to be at highest risk for serious adverse events, such as uterine cancer and thromboembolic phenomena. Individuals in whom tamoxifen-associated breast cancer risk reduction appears to outweigh risk of serious side-effects include women with prior in situ or estrogen receptor (ER)-positive invasive cancer, atypical hyperplasia, and/or women ages 35-49 with a calculated Gail 5-year risk of > or =1.7%, hysterectomized women aged 50 and older with a 5-year Gail risk of > or =2.5%, and nonhysterectomized women aged 50 and older with a 5-year Gail risk of >5.0%. It is not yet clear whether tamoxifen can reduce breast cancer incidence in women with BRCA1 and BRCA2 mutations, although preliminary evidence favors benefit for at least those with a BRCA2 mutation. Raloxifene is a selective ER modulator with less uterine estrogen agonist activity than tamoxifen, and it is hoped that it will result in fewer uterine cancers but will be equally efficacious in reducing the risk of breast cancer. The NSABP is currently conducting a randomized study of tamoxifen versus raloxifene in high-risk postmenopausal women. Approximately one third of invasive cancers are ER negative. Tamoxifen does not reduce the incidence of ER-negative cancers, nor does it appear to be effective in preventing the appearance of one third of ER-positive cancers. Priorities in prevention research are to develop (a) biomarkers to refine short-term risk assessments based on epidemiologic models, (b) biomarkers predictive of response to specific classes of preventive agents, (c) drugs with fewer side-effects and/or effective in ER-negative or ER-positive tamoxifen-resistant precancerous disease, and (d) efficient clinical trial models to assess new agent efficacy. Breast intraepithelial neoplasia (IEN) may be sampled by minimally invasive techniques and is an attractive short-term risk biomarker. Molecular abnormalities observed in IEN may be used to select potential agents for testing/therapy, and modulation of these abnormalities may be used in phase I trials to select appropriate doses and in phase II trials to assess response. Breast density volume and certain serum markers such as insulin-like growth factor-1 are also being studied as potential risk and response biomarkers. Reversal or prevention of advanced IEN as well as modulation of other risk biomarkers in randomized phase II and phase III trials is being evaluated as a means of more efficiently evaluating prevention drugs in the future. A number of agents are being developed that target molecular abnormalities in IEN, have fewer or different side effects than tamoxifen, and may be effective in ER-negative or tamoxifen-resistant disease.

Epidemiology, prevention, and early detection of breast cancer

Decreases in the incidence of breast cancer have not been achieved, but there is a downward trend in age-adjusted breast cancer mortality rates in the United States. Recent epidemiologic investigations continue to refine our understanding of the role of established breast cancer risk factors, such as reproductive characteristics and body mass index, and in the process advance understanding of the etiology of breast cancer. Important strides are being made in the chemoprevention of breast cancer, but clarifying the potential contributions of factors such as diet, physical activity, and cigarette smoke to the breast cancer burden is a high priority because these lifestyle behaviors also have important implications for primary prevention. The role of both environmental and endogenous exposures in breast carcinogenesis will be more clearly elucidated by studies that account for genetic polymorphisms, some of which may lead to differential susceptibility to harmful agents.

Chemoprevention of breast cancer

Despite a recent trend toward improvement in the U.S. breast cancer mortality rate, breast cancer incidence (182,800 new cases anticipated in 2000) and mortality figures (over 40,800 anticipated deaths) remain the highest and second highest, respectively, of all cancers in U.S. women. In 1998, the selective-estrogen-receptor-modulator (SERM) tamoxifen achieved positive results in the Breast Cancer Prevention Trial (BCPT), leading to the Food and Drug Administration (FDA) approval of tamoxifen for risk reduction in women at high risk of breast cancer (the historic first FDA approval of a cancer preventive agent). This brought about a paradigm shift in new approaches for controlling breast cancer toward pharmacologic preventive regimens, called chemoprevention. This paper presents a comprehensive clinical review of breast cancer prevention study, highlighting issues of the extensive study of tamoxifen. These issues include the record of primary tamoxifen results in several breast-cancer risk-reduction settings (primary, adjuvant, and ductal carcinoma in situ [DCIS]); critical secondary BCPT risk-benefit findings (including quality of life issues) and their effects on counseling patients on use of tamoxifen for prevention; ethic minorities; optimal tamoxifen dose/duration; and potential impact on mortality and other issues involved with potential net benefit to society. Other breast-cancer chemoprevention issues reviewed here include women at high genetic risk (especially BRCA1 mutation carriers); raloxifene in breast cancer prevention; other SERMs; SERM resistance; and new agents and combinations currently in development. Very recent developments involving PPAR-gamma ligands, COX-2 inhibitors, and RXR-ligands are discussed in the section on new drug development.