Breast cancer chemoprevention. Tamoxifen: current issues and future prospective

Attitudes toward participation in breast cancer randomized clinical trials in the African American community: a focus group study

Participation of African Americans in research trials is low. Understanding the perspectives of African American patients toward participation in clinical trials is essential to understanding the disparities in participation rates compared with whites. A qualitative study was conducted to discover attitudes of the African American community regarding willingness to participate in breast cancer screening and randomized clinical trials. Six focus groups consisting of 8 to 11 African American women (N = 58), aged 30 to 65, were recruited from local churches. Focus group sessions involved a 2-hour audio-taped discussion facilitated by 2 moderators. A breast cancer randomized clinical trial involving an experimental breast cancer treatment was discussed to identify the issues related to willingness to participate in such research studies. Six themes surrounding willingness to participate in randomized clinical trials were identified: (1) Significance of the research topic to the individual and/or community; (2) level of trust in the system; (3) understanding of the elements of the trial; (4) preference for "natural treatments" or "religious intervention" over medical care; (5) cost-benefit analysis of incentives and barriers; and (6) openness to risk versus a preference for proven treatments. The majority (80%) expressed willingness or open-mindedness to the idea of participating in the hypothetical trial. Lessons learned from this study support the selection of a culturally diverse research staff and can guide the development of research protocols, recruitment efforts, and clinical procedures that are culturally sensitive and relevant.

Challenges to evidence-based medicine: a comparison of patients and treatments in randomized controlled trials with patients and treatments in a practice research network

BACKGROUND

The practice of evidence-based medicine depends on the availability of clinically relevant research, yet questions have been raised about the generalizability of findings from randomized controlled trials (RCTs).

OBJECTIVES

The aim of this study was to quantify differences between RCT patients and treatments and those in day-to-day clinical practice.

RESEARCH DESIGN

Data from published reports of two key RCTs underlying recent treatment advances in psychiatry were compared with data on routine psychiatric practice collected through a Practice Research Network (PRN).

SETTING

Hospital inpatient units (RCT) and the full range of psychiatric practice settings in the United States (PRN).

SUBJECTS

Adults with bipolar I disorder and adults with schizophrenia.

MEASURES

Demographic (age, gender, race), clinical (principal diagnoses, comorbid conditions, psychosocial functioning, and histories of hospitalization), and treatment (medication name and dosage) characteristics.

RESULTS

PRN patients had more comorbid conditions and were more likely to be white, female, and older than RCT patients. In all, 38% of PRN patients with schizophrenia and 55% of PRN patients with bipolar I disorder would have been ineligible for the corresponding RCT. Most PRN patients receiving an RCT study medication were also receiving other medications not allowed by the RCT protocol.

CONCLUSIONS

Findings support the assertion that RCT patients and treatments are not typical of those in clinical practice, and most patients in clinical practice are receiving treatments that do not have direct empirical support. Research is needed to determine the extent to which RCT findings should be used to guide routine clinical decisions.

CYP2D6-mediated catalysis of tamoxifen aromatic hydroxylation with an NIH shift: similar hydroxylation mechanism in chicken, rat and human liver microsomes

1. 4-Tritiated-tamoxifen (4-[(3)H]-tamoxifen) and 4-deuterated-tamoxifen (4-[(2)H]-tamoxifen) were synthesized to examine tamoxifen metabolism by human P450 (CYP) forms and also for the possibility of determining tamoxifen-4-hydroxylation in humans in vivo. 2. Liver microsomes from several species and cDNA-expressed human P450s were incubated with 4-[(3)H]-tamoxifen and the reaction monitored by assaying 4-hydroxytamoxifen (4-OH-tam) and (3)H(2)O formed. However, tamoxifen-4-hydroxylation did not generate stoichiometric amounts of (3)H(2)O and the expected unlabelled 4-OH-tam but instead yielded radiolabelled 4-OH-tam, apparently from [(3)H]-migration to the ortho-position, referred to as the NIH shift. 3. CYP2D6 was the prime catalyst of tam-4-hydroxylation, whereas CYP2B6, 2C9 and 2C19 yielded only low levels of 4-OH-tam; nevertheless, in all cases the 4-OH-tam was radioactive, apparently resulting from reactions involving an NIH shift. 4. Chicken liver microsomal preparation, being catalytically the most active in tamoxifen-4-hydroxylation, was incubated with deuterated tamoxifen (4-[(2)H]-tamoxifen) in order to determine whether an NIH shift occurs. Ion-trap mass-spectrometry of the HPLC-purified 4-OH-tam, from that incubation, indicated about 60% of [(2)H]-retention in 4-OH-tam, signifying an NIH shift. These findings indicate that the aromatic hydroxylation of tamoxifen does not entail hydroxyl insertion with an Sn2-displacement of hydrogen or a hydrogen isotope ((2)H or (3)H), but apparently involves epoxidation followed by migration of the (3)H, (2)H or (1)H to the ortho-position, and dissociation of the (1)H in preference to (3)H or (2)H, i.e. retention of the hydrogen isotope appears to be related to the bond strengths: C-(3)H>C-(2)H>C-(1)H.

Breast tissue density quantification via digitized mammograms

Studies reported in the literature indicate that breast cancer risk is associated with mammographic densities. An objective, repeatable, and a quantitative measure of risk derived from mammographic densities will be of considerable use in recommending alternative screening paradigms and/or preventive measures. However, image processing efforts toward this goal seem to be sparse in the literature, and automatic and efficient methods do not seem to exist. In this paper, we describe and validate an automatic and reproducible method to segment dense tissue regions from fat within breasts from digitized mammograms using scale-based fuzzy connectivity methods. Different measures for characterizing mammographic density are computed from the segmented regions and their robustness in terms of their linear correlation across two different projections--cranio-caudal and medio-lateral-oblique--are studied. The accuracy of the method is studied by computing the area of mismatch of segmented dense regions using the proposed method and using manual outlining. A comparison between the mammographic density parameter taking into account the original intensities and that just considering the segmented area indicates that the former may have some advantages over the latter.

American Society of Clinical Oncology technology assessment on breast cancer risk reduction strategies: tamoxifen and raloxifene

OBJECTIVE

To conduct an evidence-based technology assessment to determine whether tamoxifen and raloxifene as breast cancer risk-reduction strategies are appropriate for broad-based conventional use in clinical practice.

POTENTIAL INTERVENTION

Tamoxifen and raloxifene.

OUTCOME

Outcomes of interest include breast cancer incidence, breast cancer-specific survival, overall survival, and net health benefits.

EVIDENCE

A comprehensive, formal literature review was conducted for tamoxifen and raloxifene on the following topics: breast cancer risk reduction; tamoxifen side effects and toxicity, including endometrial cancer risk; tamoxifen influences on nonmalignant diseases, including coronary heart disease and osteoporosis; and decision making by women at risk for breast cancer. Testimony was collected from invited experts and interested parties.

VALUES

More weight was given to publications that described randomized trials. BENEFITS/HARMS/COSTS: The American Society of Clinical Oncology (ASCO) Working Group acknowledges that a woman's decision regarding breast cancer risk-reduction strategies will depend on the importance and weight attributed to the information provided regarding both cancer and non-cancer-related risks.

CONCLUSIONS

For women with a defined 5-year projected risk of breast cancer of >/= 1.66%, tamoxifen (at 20 mg/d for up to 5 years) may be offered to reduce their risk. It is premature to recommend raloxifene use to lower the risk of developing breast cancer outside of a clinical trial setting. On the basis of available information, use of raloxifene should currently be reserved for its approved indication to prevent bone loss in postmenopausal women. Conclusions are based on single-agent use of the drugs. At the present time, the effect of using tamoxifen or raloxifene with other medications (such as hormone replacement therapy), or using tamoxifen and raloxifene in combination or sequentially, has not been studied adequately. The continuing use of placebo-controlled trials in other risk-reduction trials highlights the current unanswered issues concerning the use of such interventions, especially when the influence on net health benefit remains to be determined. Breast cancer risk reduction is a rapidly evolving area. This technology assessment represents an ongoing process with existing plans to monitor and review data and to update recommendations in a timely matter. (See

VALIDATION

The conclusions of the Working Group were evaluated by the ASCO Health Services Research Committee and by the ASCO Board of Directors.

SPONSOR

American Society of Clinical Oncology.

Triphenylethylene antiestrogens induce uterine vascular endothelial growth factor expression via their partial estrogen agonist activity

Estradiol induces vascular endothelial growth factor (VEGF) expression in the rat uterus and this may contribute to the hyperemia and increased vascularity produced by estrogens in this target tissue. Triphenylethylene antiestrogens such as tamoxifen have mixed agonist/antagonist activity and their specific effects are tissue and gene specific. These drugs exhibit primarily antiestrogenic actions in mammary tissue and are thus used for the treatment of breast cancer. These drugs are also suggested to be inhibitors of angiogenesis. However, uterine side effects of tamoxifen are thought to stem largely from the agonist activity of the drug in this tissue. Since side effects of tamoxifen such as uterine bleeding and endometrial cancer seem likely to have an angiogenic component, we have examined the effects of this drug, its metabolite, 4-hydroxy-tamoxifen and two additional triphenylethylene antiestrogens, nafoxidine and clomiphene, on the expression of VEGF and another estrogen regulated gene, c-fos, using the rat uterus as an experimental system. All four compounds increase uterine VEGF and c-fos mRNA levels indicating that the triphenylethylene class of antiestrogens are predominantly agonists for the induction of these genes in the uterus.

Weight gain associated with adjuvant tamoxifen therapy in stage I and II breast cancer: fact or artifact?

There is a perception that tamoxifen causes weight gain in breast cancer patients. The purpose of this research study was to determine if weight gain is associated with tamoxifen therapy and to observe the impact of weight gain on recurrence and survival. Prognostic indicators, changes in weight, and disease status from diagnosis to the end of treatment were studied in 200 consecutive Stage I and II breast cancer patients, not receiving systemic chemotherapy, admitted from 1986 to the present, with observation periods ranging from 3-5 years. A mean weight gain of 1.2 Kgs was seen in all patients; however, weight gain was not significantly different for those receiving tamoxifen vs. those not receiving tamoxifen, (P = 0.66, CI 95% for the difference -1.8 Kgs to +1.2 Kgs). Weight gain during treatment with tamoxifen was not correlated with treatment duration or with recurrence or survival. Age at diagnosis was positively correlated to weight gain in all groups. Our data failed to show that tamoxifen is associated with weight gain. The moderate weight gain observed in this patient population is comparable to the general aging disease-free population and may no be treatment-related. These findings may help to alleviate some concerns of both physicians and patients when tamoxifen is the drug of choice for adjuvant therapy.

Ovarian status influences the skeletal effects of tamoxifen in adult rats

Tamoxifen (TAM), an antiestrogen used in adjuvant therapy for breast cancer, is currently being evaluated for prevention of breast cancer in premenopausal and postmenopausal disease-free women. In light of this clinical application in young women, the skeleton's potential predisposition for osteoporosis following long-term treatment with an antiestrogen is a concern. In postmenopausal women being treated for breast cancer TAM was shown to prevent bone loss. There is little information, however, about the skeletal effects of TAM in premenopausal women. Previous animal studies in ovariectomized (OVX'd) rats have consistently reported TAM to prevent cancellous and cortical bone loss. The effects of TAM on ovary-intact animals, however, are not well established. We have performed a histomorphometric analysis in order to evaluate the influence of ovarian function on the skeletal effects of long-term TAM treatment in the laboratory animal model. Six-month-old rats were implanted subcutaneously with pellets designed for the controlled release of TAM at a dose (5 mg/3 wks) previously shown to be effective at antagonizing short-term bone loss in OVX'd growing rats. TAM acted as an estrogen agonist on cortical bone measurements in tibia of ovary-intact as well as OVX'd rats. In cancellous bone of OVX'd rats, TAM reduced indices of bone formation and resorption and reduced the bone loss from over 90 percent to less than 50 percent. In ovary-intact rats, however, TAM produced a 31 percent loss of cancellous bone, a deficit associated with a 26 percent reduction in the trabecular number. These results clearly demonstrate an interaction between TAM and ovarian status whereby TAM partially prevents estrogen-deficient bone loss in OVX'd animals but antagonizes selective actions of estrogen on the skeleton of ovary-intact animals.

Prevention and early detection of cancer in women

Cancer remains a significant problem for women. When detected early, cancer is more easily treated and the possibility of long-term cure is greatest. Nurses play an important role in the prevention and early detection of cancer in women. Nurses can serve as role models to women by incorporating cancer prevention and detection practices into their personal health behaviors. Nurses also have many opportunities to incorporate primary, secondary, and tertiary prevention methods into their practice, regardless of the setting. The impact on quality of life and decreased mortality as a result of implementation of prevention and early detection practices is significant.

Tamoxifen and related compounds protect against lipid peroxidation in isolated nuclei: relevance to the potential anticarcinogenic benefits of breast cancer prevention and therapy with tamoxifen?

Tamoxifen, 4-hydroxytamoxifen, nafoxidine, 17 beta-oestradiol and ICI 164,384 were all found to protect rat liver nuclei against Fe(III)-ascorbate dependent lipid peroxidation. The order of effectiveness of these compounds was 4-hydroxytamoxifen > 17 beta-oestradiol > nafoxidine > tamoxifen > ICI 164,384. This protection by tamoxifen against the formation of the genotoxic reactive-intermediates and products of lipid peroxidation in the nuclear membrane could be important in the prevention of nuclear DNA damage and thus carcinogenesis. This possible anticarcinogenic benefit of tamoxifen treatment could be important in long-term therapy with tamoxifen (and future derivatives) and in its proposed use in the prevention of breast cancer.

The antioxidant action of synthetic oestrogens involves decreased membrane fluidity: relevance to their potential use as anticancer and cardioprotective agents compared to tamoxifen?

The synthetic oestrogens diethylstilboestrol, hexoestrol and 17 alpha-ethynyloestradiol are known to be good antioxidants, and we now report that they decrease membrane fluidity, in ox-brain phospholipid liposomes. The order of effectiveness was diethylstilboestrol > hexoestrol > 17 alpha-ethynyloestradiol and a good positive correlation was demonstrated between decreased membrane fluidity and antioxidant ability (measured as inhibition of liposomal lipid peroxidation: correlation coefficient, r = 0.99). This ability of diethylstilboestrol, hexoestrol and 17 alpha-ethynyloestradiol to decrease membrane fluidity is suggested, therefore, to be the mechanism of their antioxidant action. The membrane-modulating antioxidant action of these synthetic oestrogens is compared to that of tamoxifen and their potential use as anticancer and cardioprotective agents is discussed.

Behavioral science in translational research and cancer control

Behavioral science plays an integral, essential role in cancer control. This review examines that role in two broad areas: (1) in the development and implementation of cancer control technologies, and (2) in the emerging focus on the process of translating cancer research into clinical practice. In developing and implementing cancer control technologies, what we know of human processes as a result of behavioral science is identified as the common link in all stages of the cancer process (prevention, detection, treatment, rehabilitation, terminal care). The value of behavioral science is shown in conservative projections (incorporating likely rates of patient noncooperation) of the health benefits obtainable by the year 2000 if effective behavioral strategies in three key areas were broadly implemented. Smoking prevention and cessation programs could lead to 7.2 million fewer smokers; application of cancer screening programs might result in 45,000 additional 5-year cancer survivors each year; and behavioral programs could lead to improved quality of life in 150,000 patients per year who experience treatment side effects despite the use of antiemetics. Behavioral science also is shown to contribute to translational science by providing a pragmatic conceptual model for clinical practice and facilitating collaborative research between basic scientists and clinical researchers. As an example of behavioral science's contribution to translational research, behavioral issues in genetic screening for cancer risk are outlined based on the experience of several families with the BRCA1 genetic marker and patients with Huntington's disease.

Behavioral and psychosocial cancer research in the underserved. An agenda for the future

BACKGROUND

This research was undertaken to review the status of behavioral and psychosocial cancer research in the underserved.

METHODS

The author extensively reviewed the literature related to behavioral and psychosocial cancer research in the underserved for this article. The author's experience as the Principal Investigator for the only National Institutes of Health smoking cessation study targeting Asian-Americans also was used in analyzing the literature and developing an agenda for the future.

RESULTS

Two questions and accompanying agenda items were addressed. The underserved were defined, and the effect of being underserved was illustrated through their disproportionate and earlier (younger) presence in morbidity and mortality statistics. Initiating behavioral and psychosocial cancer research in the underserved begins with a proper attitude and making accommodations to culture. The agenda for research should be practical and assessed on the basis of prevalence and preventability of cancer related behaviors. Examples from underserved Asian-American populations were cited.

CONCLUSIONS

Behavioral and psychosocial cancer research needs to be done.

Tamoxifen decreases drug efflux from liposomes: relevance to its ability to reverse multidrug resistance in cancer cells?

Tamoxifen decreased the efflux of the fluorescent marker drug, chloroquine, from phosphatidylcholine liposomes. Tamoxifen is a known structural-mimic of cholesterol, which were both found to be similarly effective in preventing drug release from liposomes. This ability of tamoxifen and cholesterol to decrease drug efflux in a concentration-dependent manner is likely to arise from their known ability to decrease membrane fluidity both in liposomes and also in cancer cells. The possible importance of the ability of tamoxifen to inhibit drug efflux from liposomes in relation to its ability to reverse multidrug resistance in cancer patients caused by the efflux of cytotoxic therapeutic agents, is discussed.

Tamoxifen: new membrane-mediated mechanisms of action and therapeutic advances

Tamoxifen protects membranes and lipoprotein particles against oxidative damage. This antioxidant action is likely to contribute to the observed cardioprotective action of tamoxifen and supports the use of this compound in treating and even preventing breast cancer. Membrane-mediated mechanisms of tamoxifen action, through a putative modulation of membrane fluidity, are likely to play an important role in its anticancer action and its ability to reverse multidrug resistance, and could also lead to clinical uses as an anti-Candida and anti-viral agent. In this review, Helen Wiseman discusses the interaction of tamoxifen with membranes and lipoprotein particles, and considers the possible clinical implications.

Chemoprevention of cancer

Chemoprevention is a strategy used to block the development of cancers in human beings. This emerging field has broad potential for influencing cancer incidence rates in defined high-risk groups and the general population. In this review, we define some of the mechanisms of carcinogenesis, describe some of the genetic markers of carcinogenesis, and list possible biomarkers that may serve as surrogate end points in chemoprevention studies. A major component of this review is a description of the agents that are currently under investigation in animal systems or in human trials. They are grouped according to the agents that block or suppress mutation, such as oltipraz, selenium, vitamin C and the flavones, or according to agents that block promotion and proliferation, such as difluoromethylornithine, tamoxifen, nonsteroidal antiinflammatory drugs, and the vitamin A derivatives. We describe the issues that are considered in the design of chemoprevention trials and in the phase I, II, and III components of these trials. The following national trials are discussed: the Breast Cancer Prevention Trial, which uses tamoxifen; the Prostate Cancer Prevention Trial, which uses finasteride; and a Lung Cancer Prevention Trial, which uses 13-cis-retinoic acid. The review ends with some insights about future studies in chemoprevention.