The role of ovarian ablation in the adjuvant therapy of breast cancer

Increasing interest has emerged in the role of ovarian function suppression, which has shown equivalence to adjuvant CMF (cyclophosphamide, methotrexate, 5-fluorouracil), whether achieved by surgery or irradiation, in breast cancer patients. Studies have suggested temporary amenorrhea can confer benefit in early breast cancer, giving luteinizing hormone-releasing hormone (LH-RH) agonists an advantage over oophorectomy or radiation. Compared with no therapy, LH-RH agonists reduce risks of recurrence and death among women younger than 50 years of age who have hormone receptor-positive tumors. Trials are assessing the benefits of adding LH-RH agonists to aromatase inhibitors, tamoxifen, or after chemotherapy in women remaining premenopausal, and the necessity for adjuvant chemotherapy with combined ovarian ablation and antiestrogen therapy.     

What is the current status of ovarian suppression/ablation in women with premenopausal early-stage breast cancer?

The role of ovarian suppression/ablation (OS/OA) in premenopausal women with hormone receptor-positive breast cancer has been evolving for more than a century. It is clear that OS/OA is an effective adjuvant therapy for these women, but despite numerous studies enrolling thousands of women, many unanswered questions remain. In particular, a major question is whether additional benefit is gained with combination treatment comprising luteinizing hormone-releasing hormone (LH-RH) agonists and tamoxifen over tamoxifen alone. Ongoing trials also are assessing the coupling of aromatase inhibitors (traditionally contraindicated in these patients because of paradoxic stimulation of estrogen production) and LH-RH agonists. Any potential disease-free or overall survival advantage of combination treatment must be balanced against a possible increase in adverse effects and impairment of quality of life. This review focuses on new data on how to incorporate OS/OA into the rational treatment of this challenging patient population.     

What is the current status of ovarian suppression/ablation in women with premenopausal early-stage breast cancer?

The role of ovarian suppression/ablation (OS/OA) in premenopausal women with hormone receptor-positive breast cancer has been evolving for more than a century. It is clear that OS/OA is an effective adjuvant therapy for these women, but despite numerous studies enrolling thousands of women, many unanswered questions remain. In particular, a major question is whether additional benefit is gained with combination treatment comprising luteinizing hormone-releasing hormone (LH-RH) agonists and tamoxifen over tamoxifen alone. Ongoing trials also are assessing the coupling of aromatase inhibitors (traditionally contraindicated in these patients because of paradoxic stimulation of estrogen production) and LH-RH agonists. Any potential disease-free or overall survival advantage of combination treatment must be balanced against a possible increase in adverse effects and impairment of quality of life. This review focuses on new data regarding how to incorporate OS/OA into the rational treatment of this challenging patient population.     

Goserelin (Zoladex)--its role in early breast cancer in pre- and perimenopausal women

Current standard adjuvant therapies for premenopausal women with early breast cancer include ovarian ablation by surgery or irradiation, chemotherapy and tamoxifen. The value of ovarian ablation in prolonging the survival of premenopausal patients with early breast cancer was clearly established by the analyses performed by the Early Breast Cancer Trialists' Collaborative Group in 1996. More recently, the value of ovarian suppression using the luteinizing hormone releasing hormone analogue goserelin as adjuvant therapy in pre-/perimenopausal women with early breast cancer has been confirmed in a series of studies involving over 8000 patients. The results from these studies provide evidence that goserelin, alone or in combination with tamoxifen, is at least as effective as cytotoxic chemotherapy in patients with hormone receptor-positive tumours and is effective when used after adjuvant chemotherapy. The use of goserelin in the management of early breast cancer presents an option which can avoid the side-effects experienced with cytotoxic chemotherapy and may offer unique benefits to premenopausal patients. The consolidation of these emerging results should help in defining the optimal role for goserelin in pre-/perimenopausal patients with early breast cancer.     

Expanding role of bisphosphonates in the management of early breast cancer

Evaluation of: Gnant M, Mlineritsch B, Schippinger W et al. Endocrine therapy plus zoledronic acid in premenopausal breast cancer. N. Engl. J. Med. 360(7), 679–691 (2009)

Current expert guidelines support tamoxifen alone or tamoxifen plus ovarian suppression as adjuvant endocrine therapy for premenopausal women with hormone receptor-positive breast cancer. Aromatase inhibitors have succeeded tamoxifen as the endocrine manipulation of choice in the treatment of postmenopausal patients. However, their use as monotherapy has traditionally been contraindicated in premenopausal women because the suppression of peripheral aromatase results in reduced feedback to the hypothalamus, and an increase in ovarian stimulation. The Austrian Breast and Colorectal Cancer Study Group trial 12 randomized premenopausal women with endocrine-responsive early breast cancer receiving the luteinizing hormone-releasing hormone agonist goserelin to tamoxifen or anastrozole without finding a significant efficacy advantage for either arm. A further randomization within the study assigned patients to receive zoledronic acid or not. Intriguingly, the addition of the bisphosphonate to adjuvant endocrine therapy significantly improved disease-free survival in the trial population. These data support the hypothesis that bisphosphonates can reduce rates of distant metastases by manipulation of the bone microenvironment, or potentially, by a direct anti-tumor effect. We discuss the potential impact of this study on clinical practice and the important issue of bone health in young women with breast cancer.     

New insights on the role of luteinizing hormone releasing hormone agonists in premenopausal early breast cancer patients

Luteinising hormone releasing hormone agonists (LH-RHa) are effective in the treatment of advanced endocrine-sensitive breast cancer in premenopausal patients, but their role in the adjuvant setting has remained controversial for a long time.Tamoxifen for 5 years has been traditionally considered the standard endocrine therapy for premenopausal patients and this is still valid for many patients. However, the recently reported SOFT trial has suggested that adding ovarian function suppression (OFS) to tamoxifen could improve DFS in women at sufficient risk to warrant adjuvant chemotherapy and who remained premenopausal after this therapy. The administration of an aromatase inhibitor plus OFS represents an additional therapeutic option for hormone-receptor positive premenopausal breast cancer patients, according to the combined analysis of the SOFT and TEXT trials. Temporary ovarian suppression induced by LH-RHa has been recognized as an effective strategy to preserve ovarian function from the toxic effects of chemotherapy and is now recommended in young breast cancer patients with endocrine-insensitive tumors.In this review, we discuss recent data on the role of LH-RHa in combination with tamoxifen or with an aromatase inhibitor, and we comment on its role as a strategy to preserve ovarian function in young patients candidates for adjuvant or neo-adjuvant chemotherapy.     

LH-RH agonists offer very good protection against the adverse gynaecological effects induced by tamoxifen

This study was initiated to evaluate the efficacy of luteinizing hormone-releasing hormone (LH-RH) agonists in protecting premenopausal patients against the adverse gynaecological effects induced by tamoxifen. Between January 1998 and January 2000, 85 premenopausal breast cancer patients were included in this prospective study. All were to receive LH-RH agonists and tamoxifen for a minimum of two years. All patients underwent a pretreatment gynaecological evaluation and annual follow-up. Bone density was also measured at the start of treatment and then after 2, 3 and 4 years. Pretreatment evaluation revealed 2 polyps. At one and two years of follow-up, no abnormal symptoms were noted and echographic findings were normal. At three years of follow-up, a polyp associated with adnexal masses was discovered. Histology revealed ovarian and endometrial metastases of infiltrating lobular breast carcinoma. Bone density evaluation after 2, 3 and 4 years of treatment showed no significant bone loss. LH-RH agonists offer safe protection against the gynaecological side-effects of tamoxifen in premenopausal breast cancer patients.     

Sequential hormonal therapy for metastatic breast cancer after adjuvant tamoxifen or anastrozole

The use of adjuvant endocrine therapy in the treatment of hormone receptor-positive, early breast cancer has become important in both pre- and postmenopausal women. Tamoxifen has been the principal adjuvant hormonal therapy in pre- and postmenopausal women with hormone receptor-positive breast cancer for nearly 20 years. Recent data in premenopausal women suggest benefit from ovarian ablation with or without tamoxifen. Early results from the 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial have demonstrated that the third-generation, selective aromatase inhibitor (AI) anastrozole ('Arimidex') is a suitable alternative adjuvant therapy for postmenopausal women with hormone receptor-positive disease. After recurrence or relapse on adjuvant endocrine therapy, responses to the sequential use of additional endocrine agents are common. The increase in the number of options now available for adjuvant therapy will have important implications for the selection of the optimal sequence of endocrine agents in the treatment of recurrent breast cancer. Menopausal status is an important factor in determining the endocrine therapy that a patient receives. For premenopausal women, tamoxifen and/or a luteinizing hormone-releasing hormone agonist such as goserelin ('Zoladex') are both options for adjuvant endocrine treatment. After progression on adjuvant and first-line tamoxifen, ovarian ablation is an appropriate second-line therapy. For premenopausal women who have undergone ovarian ablation, the use of third-line therapy with an AI becomes possible. For postmenopausal women, a wide choice of endocrine treatment options is available and an optimal sequence has yet to be determined. Options for first-line therapy of metastatic disease include an AI for women who have received adjuvant tamoxifen or tamoxifen for patients who have received adjuvant anastrozole. In addition, data suggest that fulvestrant ('Faslodex'), a novel estrogen receptor (ER) antagonist that downregulates the ER protein and has no known agonist effects, is a promising therapeutic option that has shown efficacy in the treatment of postmenopausal women with advanced breast cancer. Other agents that may be used in the sequence include the steroidal AI exemestane and the progestin megestrol acetate. The widening range of adjuvant endocrine options therefore represents an opportunity to prolong patient benefits in the treatment of hormone receptor-positive breast cancer, and will require the further refinement of the optimal sequence of endocrine agents for the treatment of recurrent breast cancer.     

Current status of adjuvant endocrine therapy for hormone responsive breast cancer

Three important meetings on adjuvant hormone therapy for breast cancer were held recently: the 5th EBCTCG Meeting, NIH Consensus Meeting, 7th International Conference on Adjuvant Therapy of Primary Breast Cancer. The conclusions of these meetings are: 1. adjuvant hormone therapy should be indicated only for patients with estrogen/progesterone receptor positive cancer, 2. five years of tamoxifen is the standard care at present, 3. ovarian ablation by any means has been proved effective in premenopausal patients and LH-RH agonist should be given at least two years, and 4. aromatase inhibitors should not be used in clinical practice, because several prospective randomized trials are ongoing at present. The patients treated with LH-RH agonist combined with tamoxifen showed better relapse-free survival compared with LH-RH agonist alone in the INT-0101 trial. This was an important trial because combined hormone therapy had not been proven more effective than individual hormone therapy previously. Combined hormone therapy including LH-RH agonist may be considered in premenopausal patients. There is a growing consensus that chemotherapy is effective through the ovarian suppression. In this sense, hormonal therapy should be considered first for hormone responsive patients. On the contrary, standard chemotherapy has shifted from CMF combination to an anthracycline containing regimen. Chemoendocrine therapy may be considered in high risk patients.     

Controversies in adjuvant endocrine treatment of premenopausal women

For patients with hormone receptor-positive breast cancer, some form of endocrine therapy is central to the management of their disease. For premenopausal patients in whom estrogen synthesis occurs primarily in the ovaries, current treatment options include ovarian ablation or suppression and selective estrogen receptor modulators such as tamoxifen and toremifene. Ovarian ablation and tamoxifen have demonstrated their effectiveness in the adjuvant setting, reducing the risk of recurrence and death. However, although some studies suggest ovarian ablation results in an equivalent outcome to chemotherapy alone, studies examining the combination have not demonstrated a clear benefit with the addition of ovarian suppression to standard chemotherapy. Results from trials combining ovarian suppression with tamoxifen have also been inconclusive. Finally, although aromatase inhibitors cannot be used as monotherapy in premenopausal patients, the reduction in the risk of recurrence observed with the integration of these agents into adjuvant regimens in postmenopausal patients when compared with the standard 5 years of tamoxifen has stimulated interest in evaluating the combination of ovarian suppression with an aromatase inhibitor in premenopausal women. Several ongoing trials will investigate these combinations as well as ovarian suppression plus tamoxifen.     

Adjuvant Endocrine Therapy of Perimenopausal and Recently Postmenopausal Women With Hormone Receptor-Positive Breast Cancer

Although 5 years of tamoxifen has been the standard adjuvant endocrine therapy for premenopausal women with hormone receptor-positive breast cancer for more than 2 decades, emerging results suggest that either switching to an aromatase inhibitor after 5 years of tamoxifen when postmenopausal or continuing tamoxifen for an additional 5 years can further decrease relapse risk. As a result, more premenopausal breast cancer patients will be continuing adjuvant endocrine therapy through the menopause transition. In this setting, questions arise regarding continued tamoxifen use through 10 years and/or the timing and appropriateness of switching to an aromatase inhibitor. In addition, it is now recognized that estrogen levels substantially decline for approximately 2 years after the last menstrual period and that chemotherapy and/or tamoxifen-induced amenorrhea preclude reliable ovarian function determination. Because aromatase inhibitors are only effective in a low estrogen environment without ovarian estrogen production, determination of the optimal endocrine adjuvant therapy for perimenopausal women and those recently postmenopausal represent a challenge requiring understanding of current clinical study results and the potential for interactions among therapeutic interventions, ovarian function, and clinical outcome. Available options include tamoxifen for 10 years, tamoxifen for 5 years followed by aromatase inhibitors, tamoxifen with a luteinizing hormone-releasing hormone (LHRH) agonist, aromatase inhibitor with an LHRH agonist or aromatase inhibitor with bilateral oophorectomy. Although completed (Austrian Breast Cancer Study Group [ABCSG]-12) and ongoing (SOFT [Suppression of Ovarian Function Trial], TEXT [Tamoxifen and Exemestane Trial]) clinical trials are addressing some issues, many questions will remain requiring individualized clinical judgement. Rationale supporting the available endocrine therapy options in this setting and recommendations for clinical management follow.     

Sequencing of endocrine therapies in breast cancer--integration of recent data

A wide range of endocrine therapies has demonstrated activity in the treatment of hormone receptor-positive metastatic breast cancer and sequential tumor responses to sequential hormonal therapies are common. However, the optimal sequence of the hormonal therapies has not yet been determined. The selection of endocrine therapies in women with hormone receptor-positive breast cancer is strongly influenced by the menopausal status of the patient. For premenopausal women, tamoxifen alone or combined with ovarian suppression using a luteinizing hormone-releasing hormone (LHRH) agonist - such as goserelin or leuprolide - is an appropriate first-line hormonal therapy. Ovarian ablation or megestrol acetate is an appropriate second-line hormonal therapy for premenopausal women treated with tamoxifen as first-line therapy, or ovarian ablation plus an aromatase inhibitor (AI) or megestrol acetate for women treated with first-line tamoxifen plus an LHRH agonist. For postmenopausal women, the non-steroidal AIs anastrozole and letrozole now represent the preferred first-line hormonal treatment for metastatic breast cancer, based upon both efficacy and toxicity considerations. For second-line therapy in postmenopausal women, a number of options now exist, including tamoxifen, the steroidal AI exemestane, and the new agent fulvestrant. Fulvestrant, a novel estrogen receptor (ER) antagonist that downregulates the ER and has no known agonist effects, has been demonstrated to be at least as effective as anastrozole in postmenopausal women whose tumors progress on tamoxifen. The establishment of the optimal sequence of the endocrine therapies should offer significant benefits to women with hormone-sensitive metastatic breast cancer.     

Overview of luteinizing hormone-releasing hormone agonists in early breast cancer-benefits of reversible ovarian ablation

Goserelin ('Zoladex'), a luteinizing hormone-releasing hormone (LHRH) agonist induces reversible ovarian ablation in premenopausal women. It is the most extensively studied LHRH agonist for the treatment of breast cancer and data from a large clinical trial program show that, alone or in combination with tamoxifen, goserelin is at least as effective as cyclophosphamide-methotrexate-5-fluorouracil (CMF) chemotherapy in patients with hormone-sensitive, early disease. Furthermore, goserelin has been shown to add benefit when used in addition to standard adjuvant therapy (surgery +/- radiotherapy +/- chemotherapy +/- tamoxifen) and may be beneficial when used after chemotherapy. In patients with hormone-sensitive, early breast cancer, treatment-induced amenorrhea has been associated with an improved prognosis and goserelin provides a highly effective and reliable method of achieving amenorrhea. The reversibility of amenorrhea upon cessation of goserelin treatment may confer long-term advantages compared with permanent methods of ovarian ablation. Ultimately, patients should be provided with sufficient information on the risks and benefits of the treatment options available to them so that they can be involved in treatment decisions.     

Future possibilities in the prevention of breast cancer: Luteinizing hormone-releasing hormone agonists

The cyclic production of estrogen and progesterone by the premenopausal ovary accounts for the steep rise in breast cancer risk in premenopausal women. These hormones are breast cell mitogens. By reducing exposure to these ovarian hormones, agonists of luteinizing hormone-releasing hormone (LHRH) given to suppress ovarian function may prove useful in cancer prevention. To prevent deleterious effects of hypoestrogenemia, the addition of low-dose hormone replacement to the LHRH agonist appears necessary. Pilot data with such an approach indicates it is feasible and reduces mammographic densities.     

The use of gonadotrophin-releasing hormone (GnRH) agonists in early and advanced breast cancer in pre- and perimenopausal women

Gonadotrophin-releasing hormone (GnRH) agonists, in particular goserelin ('Zoladex'), are increasingly being used for the treatment of breast cancer in women with functioning ovaries. They act by downregulating pituitary GnRH receptors, thereby suppressing the release of luteinising hormone (LH) and follicle stimulating hormone (FSH), which, in turn, reduce the main source of oestradiol production in the ovaries. GnRH agonists have been shown to be as effective therapeutically as surgical ovarian ablation in pre- and perimenopausal women with advanced breast cancer. The combination of a GnRH agonist such as goserelin with the peripheral oestrogen antagonist, tamoxifen, may be used to produce 'combined oestrogen blockade'. In advanced breast cancer, this regimen prolongs progression-free survival and increases both the response rate and duration relative to the use of a GnRH agonist alone. In patients with early breast cancer, the addition of goserelin to 'standard treatment' (i.e. surgery+/-tamoxifen, chemotherapy or radiotherapy) results in a significant benefit in recurrence-free survival and overall survival. This benefit was most apparent in patients with oestrogen receptor (ER) +ve tumours. Goserelin, when used either alone or in combination with tamoxifen as an adjuvant systemic therapy in women with ER +ve tumours, has been shown in clinical trials to produce recurrence-free survival rates equivalent to cytotoxic chemotherapy such as cyclophosphamide, methotrexate, 5-fluorouracil (CMF). Evidence suggests that at least part of the effect of adjuvant cytotoxic chemotherapy in premenopausal women is produced by ovarian ablation. Endocrine therapy with goserelin or goserelin plus tamoxifen should now be considered a treatment option in the management of premenopausal women with ER +ve early breast cancer.     

Recent perspectives of endocrine therapy for breast cancer

The choice of endocrine therapy for breast cancer depends on the menopausal status and stage of disease. Endocrine therapy remains the first choice and most important component in the treatment of hormone sensitive non-life threatening advanced breast cancer. In premenopausal women with metastatic disease, the combination of a luteinizing hormone-releasing hormone (LH-RH) agonist plus tamoxifen is reasonable as first-line endocrine therapy. In postmenopausal patients with recurrent disease progressing after or during adjuvant tamoxifen, third-generation aromatase inhibitors (AIs) are the preferred first-line endocrine treatment. Many premenopausal and postmenopausal women with hormone responsive breast cancer benefit from sequential use of endocrine therapies at the time of disease progression. Recent clinical trials designs have been implemented, employing AIs as monotherapy in postmenopausal breast cancer patients, as first-line adjuvant therapy, and in sequence either 2-3 or 5 years, with initial tamoxifen. Emerging results from these trials indicate an advantage to patients for any of these strategies, and most international guidelines now suggest the use of an AI in the adjuvant setting in postmenopausal women. The use of endocrine treatment for metastatic and early breast cancer will be reviewed here.     

Adjuvant endocrine therapy for premenopausal women with early breast cancer

Adjuvant endocrine therapy is a pivotal component of treatment for premenopausal women with early-stage hormone receptor-positive breast cancer. Currently, the standard endocrine therapy for premenopausal women is tamoxifen; a role for ovarian suppression or ablation has also been identified. Uncertainty remains about the optimal use of endocrine therapy in this setting. The role of ovarian suppression with tamoxifen or aromatase inhibitor, the optimal duration of adjuvant endocrine therapy and the utility of biomarkers and pharmacogenetic studies to select therapy are questions worthy of further investigation.     

Endocrinology and hormone therapy in breast cancer: Endocrine therapy in premenopausal women

Endocrine therapy remains important in premenopausal women with hormone receptor positive breast cancer. Ovarian ablation, used alone, is effective in delaying recurrence and increasing survival in such women. When added to chemotherapy, it is less clear that it is effective perhaps because of the endocrine ablative effect of chemotherapy. Trials comparing ovarian ablation with or without tamoxifen to CMF-type chemotherapy suggest that the endocrine therapy is equivalent to or better than this chemotherapy in women whose tumors have estrogen and/or progesterone receptor. Tamoxifen is also effective in preventing recurrence and prolonging survival in the adjuvant setting in premenopausal women. While most of the available data deals with tamoxifen given alone, it appears to have a similar beneficial effect when added to chemotherapy in the premenopausal adjuvant setting. Adjuvant aromatase inhibitors should not be used in premenopausal women.     

Endocrinology and hormone therapy in breast cancer: endocrine therapy in premenopausal women

Endocrine therapy remains important in premenopausal women with hormone receptor positive breast cancer. Ovarian ablation, used alone, is effective in delaying recurrence and increasing survival in such women. When added to chemotherapy, it is less clear that it is effective perhaps because of the endocrine ablative effect of chemotherapy. Trials comparing ovarian ablation with or without tamoxifen to CMF-type chemotherapy suggest that the endocrine therapy is equivalent to or better than this chemotherapy in women whose tumors have estrogen and/or progesterone receptor. Tamoxifen is also effective in preventing recurrence and prolonging survival in the adjuvant setting in premenopausal women. While most of the available data deals with tamoxifen given alone, it appears to have a similar beneficial effect when added to chemotherapy in the premenopausal adjuvant setting. Adjuvant aromatase inhibitors should not be used in premenopausal women.     

Selection of optimal adjuvant endocrine therapy for early-stage breast cancer

Opinion statement Oophorectomy was found to cause regression of advanced breast cancer toward the end of the 19th century. Decades later, the discovery that estrogen plays a central role in this process eventually led to two important consequences: first, different modalities were developed to suppress or antagonize estrogen; and second, the ability to detect estrogen receptor in breast cancer tissue became a predictor of response to treatment—probably the best marker for response among all solid tumors. Tamoxifen, which works by competitively antagonizing hormonal receptors in breast cancer cells, has been for the past three decades the standard of care for adjuvant therapy for any woman with hormone receptor-positive early breast cancer, regardless of nodal status or menopausal setting. But as we strive to improve the utility of antagonizing or suppressing estrogen, new modalities are being developed. In the premenopausal setting, the advent of gonadotropin hormone-releasing hormone (also known as luteinizing hormone-releasing hormone) analogues has allowed for medical and reversible suppression of ovarian function. This method has already been proven as effective as chemotherapy in preventing recurrence, and ongoing trials are aiming to better define its role in the adjuvant setting. In the postmenopausal setting, aromatase inhibitors (AIs) have revolutionized the adjuvant treatment of hormone-responsive cancers of all stages. The current standard of care has come to include AIs, as an alternative, in sequence, of after 5 years of tamoxifen. Ongoing research continues to develop agents to overcome hormonal therapy resistance.