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Query: UMLS:C0278488 (metastatic breast cancer)
 7,812 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Breast cancer is the most common cancer and the second leading cause of cancer death in American women. It was the second most common cancer in the world in 2002, with more than 1 million new cases. Despite advances in early detection and the understanding of the molecular bases of breast cancer biology, about 30% of patients with early-stage breast cancer have recurrent disease. To offer more effective and less toxic treatment, selecting therapies requires considering the patient and the clinical and molecular characteristics of the tumor. Systemic treatment of breast cancer includes cytotoxic, hormonal, and immunotherapeutic agents. These medications are used in the adjuvant, neoadjuvant, and metastatic settings. In general, systemic agents are active at the beginning of therapy in 90% of primary breast cancers and 50% of metastases. However, after a variable period of time, progression occurs. At that point, resistance to therapy is not only common but expected. Herein we review general mechanisms of drug resistance, including multidrug resistance by P-glycoprotein and the multidrug resistance protein family in association with specific agents and their metabolism, emergence of refractory tumors associated with multiple resistance mechanisms, and resistance factors unique to host-tumor-drug interactions. Important anticancer agents specific to breast cancer are described. Breast cancer is the most common type of cancer and the second leading cause of cancer death in American women. In 2002, 209,995 new cases of breast cancer were registered, and 42,913 patients died of it. In 5 years, the annual prevalence of breast cancer will reach 968,731 cases in the United States. World wide, the problem is just as significant, as breast cancer is the most frequent cancer after nonmelanoma skin cancer, with more than 1 million new cases in 2002 and an expected annual prevalence of more than 4.4 million in 5 years. Breast cancer treatment currently requires the joint efforts of a multidisciplinary team. The alternatives for treatment are constantly expanding. With the use of new effective chemotherapy, hormone therapy, and biological agents and with information regarding more effective ways to integrate systemic therapy, surgery, and radiation therapy, elaborating an appropriate treatment plan is becoming more complex. Developing such a plan should be based on knowledge of the benefits and potential acute and late toxic effects of each of the therapy regimens. Despite advances in early detection and understanding of the molecular bases of breast cancer biology, approximately 30% of all patients with early-stage breast cancer have recurrent disease, which is metastatic in most cases. The rates of local and systemic recurrence vary within different series, but in general, distant recurrences are dominant, strengthening the hypothesis that breast cancer is a systemic disease from presentation. On the other hand, local recurrence may signal a posterior systemic relapse in a considerable number of patients within 2 to 5 years after completion of treatment. To offer better treatment with increased efficacy and low toxicity, selecting therapies based on the patient and the clinical and molecular characteristics of the tumor is necessary. Consideration of these factors should be incorporated in clinical practice after appropriate validation studies are performed to avoid confounding results, making them true prognostic and predictive factors. A prognostic factor is a measurable clinical or biological characteristic associated with a disease-free or overall survival period in the absence of adjuvant therapy, whereas a predictive factor is any measurable characteristic associated with a response or lack of a response to a specific treatment. The main prognostic factors associated with breast cancer are the number of lymph nodes involved, tumor size, histological grade, and hormone receptor status, the first two of which are the basis for the AJCC staging system. The sixth edition of the American Joint Committee on Cancer staging system allows better prediction of prognosis by stage. However, after determining the stage, histological grade, and hormone receptor status, the tumor can behave in an unexpected manner, and the prognosis can vary. Other prognostic and predictive factors have been studied in an effort to explain this phenomenon, some of which are more relevant than others: HER-2/neu gene amplification and protein expression, expression of other members of the epithelial growth factor receptor family, S phase fraction, DNA ploidy, p53 gene mutations, cyclin E, p27 dysregulation, the presence of tumor cells in the circulation or bone marrow, and perineural and lymphovascular space invasion. Systemic treatment of breast cancer includes the use of cytotoxic, hormonal, and immunotherapeutic agents. All of these agents are used in the adjuvant, neoadjuvant, and metastatic setting. Adjuvant systemic therapy is used in patients after they undergo primary surgical resection of their breast tumor and axillary nodes and who have a significant risk of systemic recurrence. Multiple studies have demonstrated that adjuvant therapy for early-stage breast cancer produces a 23% or greater improvement in disease-free survival and a 15% or greater increase in overall survival rates. Recommendations for the use of adjuvant therapy are based on the individual patient's risk and the balance between absolute benefit and toxicity. Anthracycline-based regimens are preferred, and the addition of taxanes increases the survival rate in patients with lymph node-positive disease. Adjuvant hormone therapy accounts for almost two thirds of the benefit of adjuvant therapy overall in patients with hormone-receptor-positive breast cancer. Tamoxifen is considered the standard of care in premenopausal patients. In comparison, the aromatase inhibitor anastrozole has been proven to be superior to tamoxifen in postmenopausal patients with early-stage breast cancer. The adjuvant use of monoclonal antibodies and targeted therapies other than hormone therapy is being studied. Interestingly, some patients have an early recurrence even though they have a tumor with good prognostic features and at a favorable stage. These recurrences have been explained by the existence of certain cellular characteristics at the molecular level that make the tumor cells resistant to therapy. Selection of resistant cell clones of micrometastatic disease has also been proposed as an explanation for these events. Neoadjuvant systemic therapy, which is the standard of care for patients with locally advanced and inflammatory breast cancer, is becoming more popular. It reduces the tumor volume, thus increasing the possibility of breast conservation, and at the same time allows identification of in vivo tumor sensitivity to different agents. The pathological response to neoadj uvant systemic therapy in the breast and lymph nodes correlates with patient survival. Use of this treatment modality produces survival rates identical to those obtained with the standard adjuvant approach. The rates of pathological complete response (pCR) to neoadjuvant systemic therapy vary according to the regimen used, ranging from 6% to 15% with anthracycline-based regimens to almost 30% with the addition of a noncross-resistant agent such as a taxane. In one study, the addition of neoadjuvant trastuzumab in patients with HER-2-positive breast tumors increased the pCR rate to 65%. Primary hormone therapy has also been used in the neoadjuvant systemic setting. Although the pCR rates with this therapy are low, it significantly increases breast conservation. Currently, neoadjuvant systemic therapy is an important tool in not only assessing tumor response to an agent but also studying the mechanisms of action of the agent and its effects at the cellular level. However, no tumor response is observed in some cases despite the use of appropriate therapy. The tumor continues growing during treatment in such cases, a phenomenon called primary resistance to therapy. The use of palliative systemic therapy for metastatic breast cancer is challenging. Five percent of newly diagnosed cases of breast cancer are metastatic, and 30% of treated patients have a systemic recurrence. Once metastatic disease develops, the possibility of a cure is very limited or practically nonexistent. In this heterogeneous group of patients, the 5-year survival rate is 20%, and the median survival duration varies from 12 to 24 months. In this setting, breast cancer has multiple clinical presentations, and the therapy for it should be chosen according to the patient's tumor characteristics, previous treatment, and performance status with the goal of improving survival without compromising quality of life. Treatment resistance is most commonly seen in such patients. They initially may have a response to different agents, but the responses are not sustained, and, in general, the rates of response to subsequent agents are lower. Table 1 summarizes metastatic breast cancer response rates to single-agent systemic therapy.
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PMID:Overview of resistance to systemic therapy in patients with breast cancer. 1799 29

The systemic adjuvant treatment for breast cancer is showing remarkable progress with targeted therapy, such as Trastuzumab, in addition to cytotoxic chemotherapy. The timing of adjuvant chemotherapy is also shifting from post surgery to pre surgery. In terms of adjuvant endocrine therapy for hormonal receptor positive breast cancer, Aromatase inhibitor now is established as a standard treatment for postmenopausal patients. LH-RH analog is also standard for premenopausal patients with Tamoxifen. Further, longer survival might be expected with the new combination of cytotoxic chemotherapy and Trastuzumab for locally advanced or metastatic breast cancer patients. Because the trend of systemic treatment for breast cancer patients is to focus on maintaining patients' quality of life, targeted therapy with Trastuzumab and/or new upcoming drugs (e. g., Bevacizumab, Lapatinib, Sunitinib), might be the mainstream systemic therapy. In this section, we discuss standard and new systemic therapy for primary, locally advanced, and metastatic breast cancer patients.
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PMID:[New period of systemic treatment for breast cancer]. 1879 97

Tamoxifen has played a central role in endocrine therapy for hormone-responsive breast cancer. Results of recent clinical trials have, however, clearly shown that third-generation aromatase inhibitors (AIs), such as anastrozole, letrozole and exemestane, are superior to tamoxifen in the treatment of postmenopausal patients with metastatic breast cancer, in an adjuvant setting and for early breast cancer. Many studies have been published that describe new results from clinical trials and how they fundamentally prove the efficacy of AIs. There are, however, still some unresolved issues concerning the applications of AIs, such as the optimal duration of the therapy, the optimal regimens (initial, adjuvant or switching from tamoxifen to AI), and combination with LH-RH agonists for premenopausal woman. These issues are discussed in this review. Additionally, further possibilities for the application of AIs, for example in combination therapy with pure antiestrogen aimed at complete estrogen blockade and in combination with new biological agents, as well as the pharmacogenomics of AIs will be discussed.
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PMID:Current topics and perspectives on the use of aromatase inhibitors in the treatment of breast cancer. 1881 May 76

Tamoxifen has been used as adjuvant hormonal therapy for estrogen receptor positive breast cancer for over 30 years and is also widely used for the treatment of metastatic breast cancer. Tamoxifen is metabolized to its more active form by cytochrome P450 2D6 (CYP2D6); decreases in CYP2D6 activity, either by inactivating polymorphisms or drug interactions, can reduce concentrations of tamoxifen's active metabolites. Clinical studies demonstrate that breast cancer patients treated with adjuvant tamoxifen who have decreased CYP2D6 due to genetic polymorphisms or drug interactions may have an increased risk of recurrence and reductions in disease-free survival. Pharmacogenetic testing is currently available to predict CYP2D6 phenotypes and individualize tamoxifen therapy.
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PMID:Clinical significance of CYP2D6 polymorphisms and tamoxifen in women with breast cancer. 1919 67

Tamoxifen is the most common endocrine therapy administered worldwide to women with hormone receptor-positive metastatic breast cancer or as adjuvant therapy for early stages of the disease. Tamoxifen may also be prescribed to women with ductal carcinoma in situ or to decrease the risk of breast cancer in women at high risk of developing the disease. While the use of aromatase inhibitors is increasing in the postmenopausal treatment setting, tamoxifen remains the drug of choice for premenopausal women. Several factors may contribute to reduced benefit from tamoxifen. It has been increasingly recognized in recent years that pharmacogenetics may play a role in tamoxifen's metabolism, efficacy, and safety. Cytochrome P450 (CYP) 2D6 encodes for a liver enzyme that is responsible for the conversion of tamoxifen into its active metabolite, endoxifen. Variant alleles in CYP2D6 or the use of medications that inhibit the enzyme clearly influence tamoxifen's metabolism into endoxifen. In addition, several retrospective studies suggest that variants in CYP2D6 may influence long term outcomes. In this review, we will summarize recent data that examined associations between CYP2D6 activity and effects on tamoxifen's metabolism and efficacy.
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PMID:Tamoxifen metabolism and its effect on endocrine treatment of breast cancer. 1939 43

Adjuvant hormonal therapy has been shown to decrease the risk of breast cancer recurrence and overall mortality in patients with hormone receptor-positive breast cancer. Tamoxifen has been used in this setting for many years, both in premenopausal and postmenopausal patients. Tamoxifen is not devoid of toxicity, and attempts have been made to develop newer hormonal agents with better efficacy and less toxicity. The aromatase inhibitors have shown equivalent or superior efficacy to tamoxifen in the treatment of metastatic breast cancer, and efforts are underway to determine the role of these agents in early breast cancer. The ATAC trial recently showed that use of the third-generation aromatase inhibitor anastrozole in the adjuvant setting led to a modest improvement in relapse-free survival as compared with tamoxifen. Patients treated with anastrozole were also less likely to develop uterine cancer or experience a thromboembolic event. However, patients treated with anastrozole were more likely than those treated with tamoxifen to suffer a fracture or other musculosketal problem. An ASCO technology assessment panel reviewed the relevant data and issued a consensus statement regarding the use of aromatase inhibitors in the adjuvant setting. In general, the panel favored the continued use of tamoxifen as adjuvant hormonal therapy for most postmenopausal women. Within the next few years, further data from the ATAC trial and from other trials of aromatase inhibitors in the adjuvant setting should be available to guide treatment recommendations for this patient population.
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PMID:The aromatase inhibitors as adjuvant therapy for hormone receptor-positive breast cancer. 1976 80

Tamoxifen (TAM) is a selective estrogen-receptor modulator that is widely used in the prevention and treatment of estrogen-receptor-positive breast cancer. Its use has significantly contributed to a decline in breast cancer mortality, since breast cancer patients treated with TAM for 5 years exhibit a 30-50% reduction in both the rate of disease recurrence after 10 years of patient follow-up and in the occurrence of contralateral breast cancer. However, in patients treated with TAM, there is substantial interindividual variability in the development of resistance to TAM therapy and in the incidence of TAM-induced adverse events, including deep-vein thrombosis, hot flashes, and the development of endometrial cancer. Aromatase inhibitors (AIs) have emerged as a viable alternative to TAM, working by inhibiting aromatase activity and blocking estrone/estrodiol biosynthesis in postmenopausal women. The current third-generation AIs, anastrozole, exemestane, and letrozole, were used initially for the treatment of metastatic breast cancer, demonstrating similar or greater benefit but less toxicity, compared with TAM, and are now being employed as adjuvant treatment for early breast cancer in postmenopausal women. This article will focus on the UDP-glucuronosyltransferases, a family of metabolizing enzymes that play an important role in the deactivation and clearance of TAM, anastrazole, and exemestane, and how interindividual differences in these enzymes may play a role in patient response to these agents.
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PMID:Potential role of UGT pharmacogenetics in cancer treatment and prevention: focus on tamoxifen and aromatase inhibitors. 1982 43

To undertake a systematic review of three first-line treatments (letrozole, anastrozole and exemestane) for hormone sensitive advanced or metastatic breast cancer (MBC) in post-menopausal women. We searched six databases from inception up to January 2009 for relevant trials regardless of language or publication status. Randomised controlled clinical trials assessing the safety and efficacy of first-line AIs for post-menopausal women with hormone receptor-positive (HR+, i.e. ER+ and/or PgR+) with or without ErbB2 (HER2)-positive MBC, who have not received prior therapy for advanced or metastatic disease were included. Where meta-analysis using direct or indirect comparisons was considered unsuitable for some or all of the data, we employed a narrative synthesis method. Four studies (25 papers) met the inclusion criteria. From the available evidence, it was possible to directly compare the three AIs with tamoxifen. In addition, by using a network meta-analysis it was possible to compare the three AIs with each other. Based on direct evidence, letrozole seemed to be significantly better than tamoxifen in terms of time-to-progression (TTP) (HR = 0.70 (95% CI: 0.60, 0.82)), objective response rate (RR = 0.65 (95% CI: 0.52, 0.82)) and quality-adjusted time without symptoms or toxicity (Q-Twist difference = 1.5; P < 0.001). Exemestane seemed significantly superior to tamoxifen in terms of objective response rate (RR = 0.68 (95% CI: 0.53, 0.89)). Anastrozole seemed significantly superior to tamoxifen in terms of TTP in one trial (HR = 1.42 (95% CI: 1.15, NR)), but not in the other (HR = 1.01 (95% CI: 0.87, NR)). In terms of adverse events, no significant differences were found between letrozole and tamoxifen. Tamoxifen was associated with significantly more serious adverse events in comparison with exemestane (OR = 0.61 (95% CI: 0.38, 0.97)); while exemestane was associated with significantly more arthralgia in comparison with tamoxifen (OR = 2.33 (95% CI: 1.07, 5.11)). Anastrozole was associated with significantly more total adverse events (OR = 1.04 (95% CI: 1.00, 1.09)) and hot flushes (OR = 1.39 (95% CI: 1.03, 1.89)) in comparison with tamoxifen in one trial; however, the other trial showed no significant differences in adverse events between anastrozole and tamoxifen. The indirect comparison of AIs with each other in women with post-menopausal, hormone sensitive advanced or MBC showed that letrozole and exemestane were better in terms of objective response rate than anastrozole; while the more clinically relevant outcomes overall survival (OS) and progression-free survival (PFS) showed no significant differences between AIs. OS and PFS showed no significant differences between AIs and hence based on these results a class effect for all AIs is possible. However, these results are based on indirect comparisons and a network analysis for which the basic assumptions of homogeneity, similarity and consistency were not fulfilled. Therefore, despite the fact that these are the best available data, the results need to be interpreted with appropriate caution. Head-to-head comparisons between letrozole, anastrozole and exemestane in the first-line MBC setting are warranted.
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PMID:Systematic review of aromatase inhibitors in the first-line treatment for hormone sensitive advanced or metastatic breast cancer. 2053 42

Tamoxifen, an effective and very well tolerated drug, binding specifically to the estrogen receptor, was approved for the treatment of breast cancer already more than 30 years ago, and can already be considered as a targeted drug. Targeted drugs, however, frequently refer to novel drugs directed at specific molecular structures in a predetermined manner. Trastuzumab was approved for the treatment of metastatic breast cancer in 1998. Since then, lapatinib and bevasizumab have been approved for the treatment of breast cancer. This review deals with treatment results obtained with targeted breast cancer drugs, use of these drugs and future prospects of such therapies.
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PMID:[Novel targeted drug therapies in breast cancer]. 2059 50

Tamoxifen (TAM), the clinical choice for the antiestrogen treatment of advanced or metastatic breast cancer, was formulated in nanoparticulate carrier systems in the form of poly(lactide-co-glycolide) (PLGA), poly-epsilon-caprolactone (PCL) and chitosan (CS) nanoparticles. The PLGA and PCL nanoparticles were prepared by a nanoprecipitation technique whereas the CS nanoparticles were prepared by the ionic gelation method. Mean particle sizes were under 260 nm for PLGA and PCL nanoparticles and around 400 nm for CS nanoparticles. Polydispersity indices were less than 0.4 for all formulations. Zeta potential values were positive for TAM loaded nanoparticles because of the positive charge of the drug. Drug loading values were significantly higher for PCL nanoparticles when compared to PLGA and CS nanoparticles. All nanoparticle formulations exhibited controlled release properties. These results indicate that TAM loaded PLGA, PCL and CS nanoparticles may provide promising carrier systems for tumor targeting.
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PMID:Comparative evaluation of in vitro parameters of tamoxifen citrate loaded poly(lactide-co-glycolide), poly(epsilon-caprolactone) and chitosan nanoparticles. 2128 54


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