Aromatase inhibitors in the treatment of early and advanced breast cancer

Aromatase inhibitors in the treatment of elderly women with metastatic breast cancer

The proportion of elderly women in the population is rising, and in tandem, the incidence of breast cancer rises with age. Because of health and tolerability concerns, as well as life expectancy, physicians may be reluctant to advise a standard treatment regimen for elderly patients with metastatic breast cancer. To elucidate this issue, we performed a literature review of clinical studies that included women with metastatic breast cancer who were over the age of 65. Our results show that although little clinical evidence exists, what is available suggests that standard treatment is tolerated and beneficial for patients meeting certain criteria. A geriatric assessment may identify specific patient groups (independent, dependent, or frail) and thereby guide treatment. Treatment recommendations for elderly patients with metastatic breast cancer are sparse, although first-line endocrine treatment, usually aromatase inhibitors or tamoxifen, is recommended for hormone-sensitive disease. In general, the evidence from clinical studies suggests that aromatase inhibitors are more effective than either tamoxifen or megestrol acetate as first- or second-line treatment in postmenopausal women with metastatic breast cancer. Ultimately, quality of life, treatment effects, and comorbidities are important aspects in this population and may guide treatment choice. To provide evidence-based treatment guidance, future clinical trials should include more patients over the age of 65 years.

Adjuvant aromatase inhibitor therapy: outcomes and safety

Adjuvant therapy with the third-generation aromatase inhibitors (AIs) anastrozole, letrozole, and exemestane has largely replaced the use of tamoxifen (TAM) as standard adjuvant endocrine treatment for postmenopausal women with hormone-sensitive early breast cancer. Treatment strategies investigated in large, randomized, well-controlled clinical studies include the use of an AI as an upfront replacement for TAM, as an alternative to continued treatment with TAM, and in the extended adjuvant setting after at least 5 years of TAM. The efficacy of AIs over TAM has been demonstrated, particularly in terms of improving disease-free survival (DFS), and reductions in early distant metastasis with AIs may ultimately translate into improved overall survival. As AI therapy offers prolonged DFS, safety is an important concern over the long term. The AIs are better tolerated than TAM in terms of troublesome gynecologic adverse events such as vaginal bleeding and discharge, as well as life-threatening complications such as venous thromboembolic events and endometrial cancer. On the other hand, AI therapy has been associated with losses in bone density and a potential effect on lipids and cardiovascular risk. In trials comparing AIs with TAM, only limited conclusions can be made because of the putative cardioprotective, lipid-lowering, and bone-sparing effects of TAM. Studies comparing AIs with placebo, and/or in healthy women, may be more useful in understanding the long-term safety of adjuvant AI therapy. Results of ongoing safety analyses within some of the large AI trials should provide further insight into the long-term tolerability of AI therapy in the adjuvant setting.

Initial treatment and changes in adjuvant endocrine therapy for early stage breast cancer

Clinical trials have shown that aromatase inhibitors (AIs) are an important advance in the treatment of early stage breast cancer (ESBC), but practice patterns and the impact of treatment side effects of endocrine therapy in the community setting have not been extensively explored. This retrospective chart review describes practice patterns among patients receiving adjuvant endocrine therapy for ESBC. Charts of 200 patients with confirmed stage I-IIIA breast cancer were reviewed. Patients received first-line treatment with tamoxifen (n=96) or AIs (n=104). Fifty-one patients completed a structured interview regarding symptom burden during therapy. Time to discontinuation or switching from first-line therapy did not vary by drug class (tamoxifen vs. AI). Musculoskeletal symptoms predicted time to switching among AI patients. Tamoxifen patients who switched to AIs tended to do so following clinical guidelines for use of AIs. Interview results showed that more anastrozole than tamoxifen patients cited side effects as the reason for switching.

Trends in breast cancer during three decades in Denmark: stage at diagnosis, surgical management and survival

BACKGROUND

Diagnostic and treatment of breast cancer has steadily improved in the last decades; mammography-screening, more aggressive axillary surgery and finally sentinel lymph node biopsies. This study analyses the impact of time trends in diagnostic and surgical procedures on stage at diagnosis and survival in three Danish counties in three decades.

METHODS

We compare extent of disease and outcome in three complete population-based patient cohorts with primary invasive breast cancer, diagnosed in 1986, 1996-1997 and 2002-2003; 3 385 patients, thereby comparing populations with and without centralised breast cancer management, mammography-screening, sentinel lymph node biopsies and the effect of time-period.

RESULTS

The 5-year over-all survival increased significantly (p <0.001) from 74% (70-78) in 1986 to 84% (82-86) in 2002-2003 with a corresponding increase in 10-year relative survival from 63% (58-68) in 1986 to 74% (71-77) in 1996-1997. In 1986 patients from Funen had median 10 lymph-nodes removed vs. median 5 and 7 in the other counties (p <0.001), and significantly more patients had positive lymph-nodes. In 1996-1997 the number of lymph-nodes removed increased significantly in all counties (median 12,13,14). In Funen, mammography-screening was implemented and patients had more favourable stage distribution (p <0.001). This was associated with significantly better over-all survival in univariate- but not in multivariate analysis. In 2002-2003 we found smaller tumors and more favourable stage-distribution in patients from Funen (p <0.001), and the 5-year relative survival increased to 90% (86-93). With increasing attention to the axilla more patients were found with positive nodal status, least in Funen (45% vs. 51% and 53%) (p <0.001). We found no significant differences in over-all survival according to county.

CONCLUSION

During these three decades over-all survival of breast cancer improved. In the earlier periods we found survival differences according to residence, but in the late cohort there were no difference despite better stage distribution in the county with mammography-screening.

CYP1B1 is not a major determinant of the disposition of aromatase inhibitors in epithelial cells of invasive ductal carcinoma

CYP1B1 and CYP19 (aromatase) have been shown to be expressed in breast tumors. Both enzymes are efficient estrogen hydroxylases, indicating the potential for overlapping substrate and inhibitor specificity. We measured the inhibition properties of aromatase inhibitors (AIs) against CYP1B1-catalyzed hydroxylation of 17beta-estradiol (E2) to determine whether CYP1B1 affects the disposition of AIs. In addition, we estimated the frequency of coexpression of these enzymes in breast tumor epithelium. Immunohistochemical analyses of CYP19 and CYP1B1 in a panel of 29 cases of invasive ductal carcinoma of the breast showed epithelial cell staining for CYP19 in 76% and for CYP1B1 in 97% of the samples. Statistical analysis showed no significant correlation (0.33) for positive expression of CYP19 and CYP1B1 (p > 0.07). CYP1B1 inhibition was determined for two steroidal inhibitors: formestane and exemestane and five nonsteroidal inhibitors: aminoglutethimide, fadrozole, anastrozole, letrozole, and vorozole. Of the seven compounds tested, only vorozole exhibited inhibition of CYP1B1 activity with IC(50) values of 17 and 21 microM for 4-hydroxy estradiol and 2-hydroxy estradiol, respectively. The estimated K(i) values of vorozole for E2 4- and 2-hydroxylation were 7.26 and 6.84 microM, respectively. Spectrophotometric studies showed that vorozole was a type II inhibitor of CYP1B1. This study shows that with the exception of vorozole, the aromatase inhibitors are selective for CYP19 relative to CYP1B1. Thus, although both CYP19 and CYP1B1 are expressed in a high percentage of breast cancers, CYP1B1 is not a major determinant of the disposition of AIs.

Breast cancer in elderly women. Optimizing the treatment

The elderly population is on the rise. Breast cancer is the most common cancer in western women and its incidence increases with age. Despite the epidemiological burden of this condition, there is a lack of knowledge regarding the management of older patients, as treatment planning is mainly based on personal preferences rather than hard data. Older women are often offered sub-optimal treatment when compared to their younger counterpart at any particular stage. This is due to various reasons, including the lack of scientific evidence from well-conducted clinical trials. Reluctance to prescribe systemic treatments may be explained by the complexity of cost-benefit evaluations in such patients. It is also an ethical dilemma to decide how aggressive one should be when it comes to treat cancer in the elderly in view of the higher rate of cognitive impairment and specific patients' expectations. This paper reviews the currently available evidence and attempts presenting and discussing chemoprevention of breast cancer, risk and benefit of hormone replacement therapy and the various treatment options for older women with breast cancer.

Breast Cancer in the Elderly

Screening and adjuvant postoperative therapies have increased survival among women with breast cancer. These tools are seldom applied in elderly patients, although the usually reported incidence of breast cancer is close to 50% in women 65 years or older, reaching 47% after 70 years in the updated Surveillance, Epidemiology, and End Results (SEER) database. Elderly breast cancer patients, even if in good medical health, were frequently excluded from adjuvant clinical trials. Women age 70 years who are fit actually have a median life expectancy of 15.5 years, ie, half of them will live much longer and will remain exposed for enough time to the potentially preventable risks of a relapse and specific death. In the last few years, a new concern about this issue has developed. Treatment now faces two major end points, as in younger women: to improve disease-free survival in the early stages, and to palliate symptoms in advanced disease. However, in both settings, the absolute benefit of treatment is critical because protecting quality of life and all its related aspects (especially functional status and independence), is crucial in older persons who have more limited life expectancy. Furthermore, the new hormonal compounds (aromatase inhibitors) and chemotherapeutic drugs (capecitabine, liposomal doxorubicin), are potentially less toxic than and equally as effective as older more established therapies. These new treatments bring new challenges including higher cost, and defining their benefit in elderly breast cancer must include an analysis of the cost/benefit ratio. These issues emphasize the urgent need to develop and support clinical trials for this older population of breast cancer patients both in the adjuvant and metastatic settings, a move that will take us from a prejudiced, age-based medicine to an evidence-based medicine.

Emerging principles for the development of resistance to antihormonal therapy: implications for the clinical utility of fulvestrant

We seek to evaluate the clinical consequences of resistance to antihormonal therapy by studying analogous animal xenograft models. Two approaches were taken: (1) MCF-7 tumors were serially transplanted into selective estrogen receptor modulator (SERM)-treated immunocompromised mice to mimic 5 years of SERM treatment. The studies in vivo were designed to replicate the development of acquired resistance to SERMs over years of clinical exposure. (2) MCF-7 cells were cultured long-term under SERM-treated or estrogen withdrawn conditions (to mimic aromatase inhibitors), and then injected into mice to generate endocrine-resistant xenografts. These tumor models have allowed us to define Phase I and Phase II antihormonal resistance according to their responses to E(2) and fulvestrant. Phase I SERM-resistant tumors were growth stimulated in response to estradiol (E(2)), but paradoxically, Phase II SERM and estrogen withdrawn-resistant tumors were growth inhibited by E(2). Fulvestrant did not support growth of Phases I and II SERM-resistant tumors, but did allow growth of Phase II estrogen withdrawn-resistant tumors. Importantly, fulvestrant plus E(2) in Phase II antihormone-resistant tumors reversed the E(2)-induced inhibition and instead resulted in growth stimulation. These data have important clinical implications. Based on these and prior laboratory findings, we propose a clinical strategy for optimal third-line therapy: patients who have responded to and then failed at least two antihormonal treatments may respond favorably to short-term low-dose estrogen due to E(2)-induced apoptosis, followed by treatment with fulvestrant plus an aromatase inhibitor to maintain low tumor burden and avoid a negative interaction between physiologic E(2) and fulvestrant.

Fulvestrant: pharmacologic profile versus existing endocrine agents for the treatment of breast cancer

OBJECTIVE

To compare the pharmacologic profile of fulvestrant with that of tamoxifen and the aromatase inhibitors with respect to the choice of treatment for advanced breast cancer (ABC).

DATA SOURCES

Principal literature and review articles were obtained from MEDLINE (1991-March 2006). Key search terms included fulvestrant, tamoxifen, aromatase inhibitors, pharmacology, and breast cancer. Further data sources were identified from the bibliographies of selected articles.

STUDY SELECTION AND DATA EXTRACTION

English-language preclinical and clinical research and review articles reporting pharmacologic and safety data for fulvestrant, tamoxifen, and the aromatase inhibitors were evaluated to identify relevant information. Randomized clinical trial data were preferred over preclinical or Phase I and II trial data.

DATA SYNTHESIS

A total of 52 clinical papers (including 10 reviews) and 17 clinical abstracts were evaluated reporting results from controlled Phase I-III studies and pilot studies. Eleven preclinical papers (including 2 reviews) and 6 preclinical abstracts were also included. Fulvestrant has little effect on sex hormone endocrinology, bone metabolism, and lipid biochemistry and appears unlikely to be the subject or cause of CYP3A4-mediated drug interactions. Tamoxifen has a protective effect on bone (due to its partial estrogen agonist activity) and reduces plasma low-density lipoprotein cholesterol but increases triglyceride levels. The aromatase inhibitors have variable effects on lipid profiles and sex hormone endocrinology but have detrimental effects on bone due to inhibition of estrogen synthesis. Drug interactions have been noted between tamoxifen and anticoagulants and tamoxifen and aromatase inhibitors, which may be due to CYP-mediated mechanisms.

CONCLUSIONS

Fulvestrant appears to have little effect on sex hormone endocrinology, bone metabolism, and lipid biochemistry and is unlikely to be subject to or the cause of CYP3A4-mediated drug-drug interactions. As such, fulvestrant represents a valuable new endocrine therapy for the treatment of ABC and broadens the options available to clinicians in the treatment of this disease.

High tea consumption diminishes salivary 17beta-estradiol concentration in Polish women

We hypothesized that among reproductive-age women consuming large quantities of tea, the production of estradiol would be suppressed. It has been shown that catechins and theaflavines, the major constituents of tea, inhibit aromatase, an enzyme which catalyses the conversion of androgens to oestrogens. Our study included Polish women living in urban (n 61) and rural (n 48) areas. Women collected daily saliva samples for one complete menstrual cycle and filled out dietary questionnaires. Saliva samples were analysed by RIA for concentration of 17beta-estradiol (E2). Women with high (above the median) average daily consumption of black tea had reduced levels of salivary E2 in comparison with women who drank less black tea (below the median). This effect was observed within the whole study group, as well as separately within urban (P=0.0006) and rural (P=0.013) groups. High intake of the sum of subclasses of tea catechins and epigallocatechin gallate, assessed using the United States Department of Agriculture database (http://www.nal.usda.gov), was also associated with lower concentrations of E2 within all women (P=0.01 and P=0.0001, respectively) and within the urban group (P=0.0001 and P=0.004, respectively). Similar relationships were observed between the sum of subclasses of theaflavines and thearubigines and E2 levels for the whole group (P=0.002) and for urban women (P=0.02). Women with high consumption of tea had lower levels of E2 concentration throughout the entire menstrual cycle. These results may have implications for reducing hormone-related cancer risk by a relatively easy dietary intervention.