Neoadjuvant Endocrine Therapy in Primary Breast Cancer

Outcomes of Japanese breast cancer patients treated with pre-operative and post-operative anastrozole or tamoxifen

The present study examined long-term efficacy outcomes in a subgroup of postmenopausal, estrogen receptor-positive Japanese breast cancer patients from the Pre-Operative "Arimidex" Compared with Tamoxifen trial, following pre-operative (3 months) and post-operative (5 years) adjuvant treatment with either anastrozole or tamoxifen. Patients with large, potentially operable, locally-advanced breast cancer were randomized to receive anastrozole (1 mg/day) plus tamoxifen placebo or tamoxifen (20 mg/day) plus anastrozole placebo pre-operatively. After surgery at 3 months, patients continued on the same study medication as adjuvant therapy for up to 5 years or until recurrence, intolerable toxicity or withdrawal of patient consent. Recurrence-free survival and overall survival were measured from the date of randomization to the date of recurrence or death, whichever occurred first. Patients were monitored for adverse events throughout the study period and up to 30 days following administration of the last study medication. During post-operative adjuvant therapy, 4/48 (8%) anastrozole and 25/49 (51%) tamoxifen patients experienced recurrence. There was a significant difference in recurrence-free survival between the two groups (hazard ratio 0.14; 95% confidence interval 0.05-0.41; P = 0.0003). There was a significant increase in overall survival with anastrozole (0.21; 0.05-0.96; P = 0.0436) and there were 2/48 (4%) and 10/49 (20%) deaths with anastrozole and tamoxifen, respectively. Most patients responding to pre-operative therapy remained recurrence-free. Sequential pre-operative/post-operative treatment with anastrozole resulted in lower recurrence and death rates, compared with tamoxifen.

Facilitating breast-conserving surgery and preventing recurrence: aromatase inhibitors in the neoadjuvant and adjuvant settings

Breast-conserving surgery (BCS) is an attractive option for many patients with early-stage breast cancer, because it provides a better cosmetic outcome than modified radical mastectomy, while reducing surgical morbidity. In patients with large, operable breast tumors who are ineligible for BCS, neoadjuvant therapy is a useful option for reducing the tumor size and for increasing the proportion of candidates for BCS. In patients with endocrine-responsive tumors, neoadjuvant endocrine therapy with either tamoxifen or an aromatase inhibitor (AI; anastrozole, letrozole, or exemestane) provides an alternative to neoadjuvant chemotherapy. Clinical trials have demonstrated the superiority of neoadjuvant AIs over tamoxifen in achieving a clinical response and increasing the frequency of BCS. In addition, adjuvant endocrine therapy with AIs, whether used as initial therapy instead of tamoxifen, in a switching strategy after 2-3 years of tamoxifen, or as extended adjuvant therapy after 5 years of adjuvant tamoxifen, has been shown in several randomized clinical trials to improve disease-free survival, reduce distant metastases and, in some cases, improve overall survival. The availability of the AIs for effective and well-tolerated neoadjuvant and/or adjuvant endocrine therapy represents an important advance in breast cancer treatment, and surgeons should be familiar with these new therapeutic options.

Overview of resistance to systemic therapy in patients with breast cancer

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.

The breast cancer continuum in hormone-receptor-positive breast cancer in postmenopausal women: evolving management options focusing on aromatase inhibitors

There are now a number of highly effective options for the treatment of hormone-receptor-positive breast cancer. Although tamoxifen was the standard hormonal treatment for many years, we now have another option for postmenopausal women: the third-generation aromatase inhibitors (AIs) anastrozole, exemestane and letrozole. A number of trials have investigated the use of third-generation AIs compared with tamoxifen throughout the continuum of treatment settings for postmenopausal women with breast cancer. In the neoadjuvant setting, letrozole, given for 4 months, resulted in better overall clinical response and breast-conserving surgery rates than tamoxifen. The Immediate Preoperative Anastrozole Tamoxifen or Combined with Tamoxifen trial gave anastrozole for 3 months with no difference in clinical response but significantly improved breast-conserving surgery rates. Compared with tamoxifen, anastrozole and letrozole significantly improved disease-free survival as early adjuvant treatment for hormone-receptor-positive disease. Switching to anastrozole or exemestane after 2 to 3 years of adjuvant tamoxifen for a total of 5 years of therapy was also more effective than continued tamoxifen. All three agents are approved in the early adjuvant or switching setting in the USA. Letrozole following 5 years of tamoxifen as extended adjuvant treatment improved disease-free survival and, in the node-positive subgroup, overall survival when compared with placebo. Anastrozole and letrozole are both approved for the first-line treatment of hormone-sensitive advanced breast cancer in postmenopausal women; letrozole showed an improved response rate compared with tamoxifen. Anastrozole, letrozole and exemestane are all indicated for the second-line treatment of advanced breast cancer. In summary, third-generation AIs have been shown to have superior efficacy over tamoxifen in the metastatic, neoadjuvant and adjuvant settings and to improve outcome as extended adjuvant therapy following 5 years of tamoxifen. Ongoing studies will further define the role of sequential adjuvant treatment. Appropriate duration of treatment is another important area of investigation. This review will cover hormonal therapy for postmenopausal women with breast cancer and will not address the treatment of premenopausal women.

Aromatase inhibitors in early breast cancer therapy: a variety of treatment strategies

Until recently, standard endocrine therapy for estrogen receptor-positive early breast cancer in the preoperative neoadjuvant and postoperative adjuvant settings was the selective estrogen receptor modulator tamoxifen. An alternate therapeutic approach is to suppress total-body estrogen synthesis using an aromatase inhibitor. The highly potent and specific third-generation aromatase inhibitors (anastrozole, exemestane and letrozole) have consistently demonstrated improved efficacy over tamoxifen in large randomised neoadjuvant and adjuvant clinical trials. As neoadjuvant therapy, compared with tamoxifen, all three aromatase inhibitors significantly improved breast-conserving surgery rates, but only letrozole achieved a significantly higher overall response rate. These agents have also been evaluated in three adjuvant strategies: instead of tamoxifen for 5 years, sequenced after 2-3 years of tamoxifen, or as extended adjuvant therapy following a full 5-year course of tamoxifen. In all cases, the aromatase inhibitor was significantly more effective in reducing the risk of recurrence, compared with tamoxifen in the first two approaches and with placebo or no treatment as extended therapy. Long-term aromatase inhibitor treatment is associated with less endometrial cancer, thromboembolic events and strokes than tamoxifen, but more musculoskeletal disorders and bone loss. Further investigation is focusing on identification of the patient subgroups most likely to benefit from each of these adjuvant therapy options.

Significance and problems in evaluations of pathological responses to neoadjuvant therapy for breast cancer

Neoadjuvant therapy consists of systemic drug treatments before surgery for a primary cancer. Currently, several neoadjuvant therapy regimens for breast cancer that use various cytotoxic as well as endocrine-therapeutic and molecular-targeting agents have been performed in clinical practice and/or studies. In neoadjuvant therapy, pre-treatment pathological examination using materials obtained by a core needle biopsy (CNB) is necessary, and pathological diagnosis and evaluation of the biological status, such as hormone receptors and HER-2 over-expression are confirmed. In addition, CNB in the inter-phase of chemotherapy is also thought to be useful for assessment of therapeutic effects before regimens have been completed. After surgery, the therapeutic effects of neoadjuvant therapy have been mainly evaluated on the basis of pathological findings and a pathological complete response (pCR) is considered to be the main target of neoadjuvant therapy. Results of most of clinical studies including NSABP protocol B-18 and B-27 have confirmed the prognostic significance of pCR in neoadjuvant therapy and indicated the significance of pathological evaluation. However, universally accepted pathological response criteria have not been established, but evaluations of the main invasive tumor, intraductal components and regional lymph nodes are thought to be necessary. Additionally, evaluation of the effects below pCR also need examining in a study using a mild anti-cancer drug, such as hormone-therapeutic agent, and the survival outcomes of patients below pCR need to be examined and compared between each grade.

Neoadjuvant systemic therapy for breast cancer: an overview and review of recent clinical trials

Neoadjuvant chemotherapy (NAC) is long established as part of the multi-modality management of locally advanced breast cancer or inflammatory breast cancer, leading to significantly improved outcome. Numerous recent studies have compared the use of anthracycline-based NAC with adjuvant chemotherapy in earlier-stage disease, and have shown equivalent disease-free and overall survival rates with increased breast conservation rates. These studies have also shown that a pathological complete response after NAC is associated with improved long-term outcome. More recently, the taxanes have been introduced into clinical trials of NAC with increased overall and pCR rates. However, there is no evidence that the addition of taxanes to neoadjuvant anthracycline-based chemotherapy significantly improves long-term disease free survival or overall survival. This paper reviews these trials, as well as trials of dose-dense and trastuzumab-containing NAC regimens. The review discusses the potential for NAC to replace prolonged adjuvant trials in the assessment of new therapeutic agents (using pathological complete response as a surrogate for long-term outcome), to be used as an in vivo chemosensitivity assay to guide further treatment, and to identify molecular markers that correlate with tumour sensitivity or resistance to chemotherapeutic agents so that the treatment of patients can be individualised.

Review of the development of letrozole and its use in advanced breast cancer and in the neoadjuvant setting

Five years of adjuvant endocrine therapy with the antiestrogen tamoxifen has been shown to significantly reduce the risk of recurrence in women with early breast cancer and has thus been the standard of adjuvant therapy for this malignancy over the last two decades. Tamoxifen has also been used for the first-line treatment of advanced or metastatic breast cancer, and it was studied in the neoadjuvant setting to promote breast-conserving surgery in those patients who may be otherwise ineligible. However, comparative clinical trials involving the more recently approved third-generation aromatase inhibitor drugs (anastrozole, letrozole, and exemestane) have challenged tamoxifen as first-line therapy in advanced/metastatic breast cancer as well as in the neoadjuvant setting. Although trials with other AIs have shown improved efficacy and better tolerability over tamoxifen, letrozole has consistently demonstrated superiority over tamoxifen when used as first-line treatment for advanced/metastatic breast cancer or as neoadjuvant therapy. The efficacy of letrozole in the neoadjuvant setting further extends to those tumors with positive human epidermal growth factor receptor (HER1) and/or HER2 expression, which are often less responsive to tamoxifen. The encouraging results of such trials identify letrozole as a better alternative to tamoxifen in improving responses rates in the treatment of advanced breast cancer and as neoadjuvant therapy, which allows breast-conserving surgery in women with inoperable breast cancer or who were not candidates for breast-conserving surgery.