Strategies for the prevention of treatment-related bone loss in women receiving adjuvant hormonal therapy

More than 220,000 women will be diagnosed with breast cancer this year, and approximately 75% of these women will be long-term survivors of this disease. Survival has improved largely because of advances in adjuvant hormone therapy and chemotherapy, as well as early detection strategies. Because most women will receive adjuvant treatment, and the majority will survive cancer, it is increasingly important to understand the resultant toxicities and to devise monitoring and treatment strategies to avoid adverse long-term effects. Loss of bone mineral density leading to osteoporosis and increased risk of fracture as well as other morbidities is a well known complication of estrogen suppression associated with use of aromatase inhibitors (AIs) in postmenopausal women, and ovarian suppression with GnRH agonists or chemotherapy in premenopausal women. Hormone receptor positivity is increasingly frequent with increasing patient age, so that a large number of women already at risk for osteopenia associated with menopause are at risk for further bone loss caused by adjuvant hormone therapy with AIs. This article will review data on bone mineral density loss and risk of fracture in the large, randomized phase III trials comparing tamoxifen to AIs using the upfront, switching or extended hormone therapy approach. Data from prophylactic bisphosphonate intervention trials in both post- and premenopausal women will be discussed. Ongoing trials are described.     

Managing bone loss in women with early-stage breast cancer receiving aromatase inhibitors

Third-generation aromatase inhibitors (AIs; anastrozole, letrozole, exemestane) have replaced tamoxifen as the adjuvant treatment of choice for postmenopausal women with hormone receptor-positive early-stage breast cancer. Because bone loss is a predictable adverse event of AI therapy, early recognition, prevention, and/or treatment of AI-induced bone loss is needed. One to 5 years of AI therapy causes a bone mineral density (BMD) loss of up to 7.2% in postmenopausal women; however, current clinical guidelines do not recommend initiating bisphosphonate therapy for the treatment of BMD loss until fragility fractures or frank osteoporosis occur. Results of recent trials evaluating the use of intravenous (I.V.) zoledronic acid as prevention and treatment of AI-induced bone loss in women with early-stage breast cancer receiving letrozole suggest a potential benefit to the concurrent use of zoledronic acid and letrozole. To our knowledge, clinical trials assessing oral or other I.V. bisphosphonates for these indications have not been published. Recently, concerns of bisphosphonate-induced renal safety and osteonecrosis of the jaw have emerged. Studies evaluating bisphosphonates in women with breast cancer have reported lower rates of renal dysfunction than those reported in patients with metastatic cancer receiving bisphosphonates, and no cases of jaw osteonecrosis. The use of bisphosphonates in this population requires further study to more clearly define the most appropriate timing and length of therapy as well as the long-term efficacy and safety of these drugs. Until these data become available, balancing the safety concerns with the potential benefits of I.V. bisphosphonates to minimize or prevent AI-induced bone loss in women with early-stage breast cancer is required.     

Bone health in women with early-stage breast cancer

Bone health is an increasingly important concern in breast cancer survivors because in postmenopausal women, bone-sparing tamoxifen is being replaced by aromatase inhibitors, whereas in premenopausal women, ovarian suppression is playing an increasing role in adjuvant management. Estrogen reduction resulting from aromatase inhibition and ovarian suppression are associated with loss in bone mineral density (BMD) and an increase in fracture risk. These side effects must be placed in context of the overall risks and benefits seen with these interventions. The American Society of Clinical Oncology has outlined a management strategy for bone health maintenance in breast cancer survivors with early-stage disease that incorporates baseline and ongoing screening for BMD and treatment based on BMD results. Limited but consistent data suggest bisphosphonate therapy represents a treatment option for this condition. A variety of interventions to maintain bone health in breast cancer survivors are undergoing clinical evaluation and include the oral bisphosphonates risedronate and clodronate, the intravenous bisphosphonate zoledronic acid, the receptor activator of nuclear factor-kB ligand inhibitor AMG-162, and the hormonal agent tibolone. Current information suggests bone loss associated with estrogen reduction in breast cancer survivors may represent a preventable and treatable condition. Ongoing clinical trials will definitively evaluate this hypothesis.     

Immediate Administration of Zoledronic Acid Reduces Aromatase Inhibitor-Associated Bone Loss in Postmenopausal Women With Early Breast Cancer: 12-month analysis of the E-ZO-FAST trial

BackgroundLetrozole is a proven and effective adjuvant therapy in postmenopausal women with hormone receptor–positive (HR⁺) early breast cancer (EBC). As with other aromatase inhibitors (AIs), long-term letrozole administration is associated with decreased bone mineral density (BMD) and increased fracture risk. This study compared potential bone-protecting effects of immediate vs. delayed administration of zoledronic acid (ZOL) in patients with EBC receiving adjuvant letrozole.Patients and MethodsPatients with HR⁺ EBC in whom adjuvant letrozole treatment was initiated (2.5 mg/day for 5 years) were randomized to immediate ZOL treatment (immediate ZOL) or delayed ZOL treatment (delayed ZOL) (both at 4 mg every 6 months). Patients in the delayed ZOL group received ZOL only for a BMD T-score that decreased to < –2.0 (lumbar spine [LS] or total hip [TH]) or for fracture. The primary endpoint was percentage change in the LS BMD at month 12. Patients were stratified by established or recent postmenopausal status, baseline T-scores, and adjuvant chemotherapy history.ResultsAt 12 months, the LS BMD increased in the immediate ZOL group (+2.72%) but decreased in the delayed ZOL group (–2.71%); the absolute difference between groups was significant (5.43%; P < .0001). Across all subgroups, patients receiving immediate ZOL had significantly increased LS and TH BMD vs. those who received delayed ZOL (P < .0001). Differences in fracture incidence or disease recurrence could not be ascertained because of early data cutoff and low incidence of events. Adverse events were generally mild, transient, and consistent with the known safety profiles of both agents.ConclusionImmediate ZOL administration effectively prevented BMD loss and increased BMD in postmenopausal women with HR⁺ EBC receiving adjuvant letrozole, regardless of BMD status at baseline.     

Adjuvant bisphosphonates in endocrine-responsive breast cancer: what is their place in therapy?

Recent advances in the treatment of early breast cancer have improved clinical outcomes and prolonged survival, especially in women with endocrine-responsive disease. However, cancer therapies including cytotoxic chemotherapy, ovarian suppression, and aromatase inhibitors can drastically reduce circulating estrogen, increasing bone loss and fracture risk. Because most women with early breast cancer will live for many years, it is important to protect bone health during cancer therapy. Several recent clinical trials combining adjuvant endocrine therapy with bisphosphonates have demonstrated efficacy for preventing cancer treatment-induced bone loss in pre- and postmenopausal women with early breast cancer. The largest body of evidence supporting the use of adjuvant bisphosphonates comes from studies with zoledronic acid; however, studies with risedronate, ibandronate, and denosumab (a biologic agent) have also demonstrated efficacy for preventing bone loss. Adding zoledronic acid to endocrine therapy prevents bone loss and improves bone mineral density (BMD). In addition, preclinical studies suggest that bisphosphonates have direct and indirect antitumor activity, such as inducing tumor cell apoptosis, reducing tumor cell adhesion and invasion, reducing angiogenesis, activating immune responses, and synergy with chemotherapy agents, among others. Clinical trials have demonstrated significantly improved disease-free survival in patients receiving adjuvant endocrine therapy plus zoledronic acid compared with endocrine therapy alone. Ongoing studies will further define the role of adjuvant bisphosphonates in maintaining bone health and improving clinical outcomes. The available evidence suggests that pre- and postmenopausal patients may receive clinical benefit from including bisphosphonates as part of their adjuvant treatment regimen for endocrine-responsive early breast cancer.     

The role of antiresorptive therapies in improving patient care in early and metastatic breast cancer

Breast cancer is the second most common cancer among American women and has a high rate of metastasis to bone. Patients regularly undergo adjuvant therapy (chemotherapy or hormonal therapy) following surgical resection of the tumor. In addition to potential direct effects on bone cells, both chemotherapy and hormonal therapy induce ovarian dysfunction and dramatically decrease estrogen levels in both pre- and postmenopausal women. This leads to decreased bone mineral density and increased fracture risk. Antiresorptive therapies (e.g, zoledronic acid and denosumab) have demonstrated efficacy in preventing cancer therapy-induced bone loss in patients with breast cancer and are approved for the prevention of skeletal-related events in patients with bone metastases from breast cancer. This review will focus on the evolving role of these antiresorptive therapies in the care of women with early or metastatic breast cancer.     

Antiresorptive therapies in oncology and their effects on cancer progression

Bone health is an emerging concern in the early breast cancer setting. Current adjuvant therapies, especially hormonal therapies in premenopausal patients (e.g. goserelin) and aromatase inhibitors in postmenopausal patients, have been associated with substantial decreases in bone mineral density that may place patients at risk for fractures. Bisphosphonates--and the recently approved anti-RANKL antibody, denosumab--have both demonstrated activity for the treatment of postmenopausal osteoporosis and cancer treatment-induced bone loss (CTIBL) in breast cancer patients, although neither has received widespread approval specifically for CTIBL. However, some bisphosphonates, especially the nitrogen-containing bisphosphonate zoledronic acid, have also demonstrated clinically meaningful anticancer effects in patients receiving adjuvant hormonal therapy for breast cancer and in other oncology settings. The effects of denosumab on cancer disease outcomes in the adjuvant setting remain to be established. This discrepancy has created a dilemma in terms of how to evaluate the complete benefit:risk profile of bone-health management options in the adjuvant breast cancer setting. This review summarises the current data on the course of cancer in clinical trials of the antiresorptive agents and provides important insight into the relative anticancer potential of the various therapies.     

Efficacy of zoledronic acid in postmenopausal women with early breast cancer receiving adjuvant letrozole: 36-month results of the ZO-FAST Study

BackgroundAromatase inhibitors (AIs) are accepted as adjuvant therapy for postmenopausal women (PMW) with hormone-responsive early breast cancer (EBC) with superior efficacy to tamoxifen. However, increased bone loss is associated with AIs.Patients and methodsPMW with EBC receiving letrozole (2.5 mg/day for 5 years) were randomly assigned to immediate zoledronic acid (ZOL; 4 mg every 6 months) or delayed ZOL (initiated only for fracture or high risk thereof).ResultsPatients (N = 1065) had a median age of 58 years; 54% had received prior adjuvant chemotherapy. At 36 months, mean change in L2-L4 bone mineral density (BMD) was +4.39% for immediate versus -4.9% for delayed ZOL (P < 0.0001). Between-group differences were 5.27% at 12 months, 7.94% at 24 months, and 9.29% at 36 months (P < 0.0001 for all). At 36 months, the immediate-ZOL group had a significant 41% relative risk reduction for disease-free survival (DFS) events (P = 0.0314). Adverse events are consistent with the known safety profiles of the study drugs.ConclusionsAt 36 months, immediate ZOL was more effective in preserving BMD during letrozole therapy. Immediate versus delayed ZOL led to significantly improved DFS. Benefits are observed in the context of a favorable, well-established safety profile for letrozole and ZOL.     

Management of aromatase inhibitor-associated bone loss in postmenopausal women with breast cancer: practical guidance for prevention and treatment

BackgroundBone mineral density (BMD)-based guidelines for bone-directed therapy in women with early breast cancer (EBC) appear inadequate for averting fractures, particularly during aromatase inhibitor (AI) therapy. Therefore, an algorithm was developed to better assess risk and direct treatment (Hadji P, Body JJ, Aapro MS et al. Practical guidance for the management of aromatase inhibitor-associated bone loss. Ann Oncol 2008; 19: 1407–1416). Here, we provide updated guidance on pharmacologic interventions to prevent/treat aromatase inhibitor-associated bone loss (AIBL).DesignSystematic literature review identified recent advances in preventing/treating AIBL. Individual agents were assessed based on trial size, design, follow-up, and safety.ResultsFracture risk factors in patients with EBC remain unchanged (Hadji P, Body JJ, Aapro MS et al. Practical guidance for the management of aromatase inhibitor-associated bone loss. Ann Oncol 2008; 19: 1407–1416). The World Health Organization Fracture Risk Assessment Tool algorithm includes fracture risk factors plus BMD but does not adequately address AIBL effects. Several antiresorptives can prevent/treat AIBL. However, concerns regarding compliance and long-term efficacy/safety remain. Overall, evidence is strongest for twice-yearly zoledronic acid (ZOL), and recent advances support additional anticancer benefits from ZOL.ConclusionsAll patients initiating AIs need advice regarding exercise, calcium/vitamin D supplements, baseline BMD monitoring (when available), and bone-directed therapy if T-score <-2.0 or at least two fracture risk factors were observed. Patients with T-score > -2.0 and no risk factors should be managed based on BMD loss during years 1–2. Unsatisfactory compliance/decreasing BMD after 12–24 months on oral bisphosphonates should trigger a switch to i.v. bisphosphonate.     

Minimizing early relapse and maximizing treatment outcomes in hormone-sensitive postmenopausal breast cancer: efficacy review of AI trials

Breast cancer is one of the leading causes of cancer-related deaths in women. Regardless of prognosis, all women with breast cancer are at risk for early recurrence. Nearly 50% of early recurrences occur within 5 years of surgery, and they peak at 2 years after surgery in women treated with adjuvant tamoxifen. Most early recurrences are distant metastases, which strongly correlate with increased mortality. Treatments that mitigate the risk of early distant metastases (DM) are, therefore, likely to improve overall survival in women with early breast cancer (EBC). Aromatase inhibitors (AIs)—anastrozole, letrozole, and exemestane—have been investigated as alternatives to tamoxifen for adjuvant treatment of hormone receptor-positive (HR+) EBC in postmenopausal women (PMW). AIs are better at minimizing risk of early relapse compared with tamoxifen. However, it is not clear if preferential use of AIs over tamoxifen will benefit all PMW with HR+ EBC. The ability to subtype HR+ breast cancer on the basis of biomarkers predictive of response to AIs and tamoxifen would likely be key to determining the most beneficial hormonal treatment within patient subpopulations, but this process requires thorough investigation. Until then, adjuvant therapies that provide the greatest reduction in risk of DM should be considered for all PMW with HR+ EBC. This article reviews the clinical trials of AI adjuvant therapies for hormone-sensitive breast cancer, particularly in the context of how they compare with tamoxifen in minimizing the risk of relapse, occurrence of DM, and breast cancer-related deaths.     

Bisphosphonates as adjuvant therapy for breast cancer

Breast cancer is the most common malignancy among women worldwide. Emerging results from clinical trials in patients with breast cancer suggest that, in addition to preventing cancer treatment-induced bone loss, bisphosphonates may improve disease-free survival (DFS). Although the first adjuvant studies using the early generation oral bisphosphonate clodronate suggested potential reductions in distant recurrence versus placebo in patients with early breast cancer, subsequent results with clodronate were inconsistent, and oral pamidronate produced no disease recurrence benefits versus chemotherapy alone in this setting. In contrast, addition of the newer bisphosphonate zoledronic acid to adjuvant therapy reduced disease recurrence rates and improved DFS compared with adjuvant endocrine therapy alone in two phase 3 studies in postmenopausal women with early breast cancer. Adjuvant zoledronic acid also significantly improved DFS compared with endocrine therapy alone in premenopausal women with breast cancer. Data from ongoing and future trials will further define the role of bisphosphonates in the adjuvant breast cancer setting.     

唑来膦酸在早期乳腺癌中的抗肿瘤研究进展

早期乳腺癌在接受辅助治疗（化疗和内分泌治疗）时均会对患者骨密度造成不良影响,加速骨丢失。第三代双磷酸盐—唑来膦酸其作用机制是抑制破骨细胞介导的骨质重吸收,主要用于恶性肿瘤骨转移引起的高钙血症。唑来膦酸-弗隆辅助协同试验（ZO-FAST）显示唑来膦酸在早期乳腺癌辅助内分泌治疗同时使用不仅可有效防止骨质丢失,还具有明显降低肿瘤复发的作用。奥地利乳腺癌和结直肠癌研究小组-12（ABCSG-12）试验结果同样表明唑来膦酸在联合内分泌治疗时可显著降低患者的疾病进展风险和死亡风险。除此之外,临床前实验和临床试验也证实唑来膦酸联合化疗也具有协同的抗肿瘤作用。唑来膦酸联合新辅助化疗降低复发（AZURE试验）,对于绝经5年以上和年龄>60岁的人群,辅助化疗加唑来膦酸显著减低疾病进展和死亡风险。在ABCSG-12试验中同样发现对于年龄>40岁的患者,唑来膦酸可明显降低复发风险,而年龄≤40岁患者却未在唑来膦酸的治疗中获益。这些结果表明唑来膦酸在雌激素低水平（自然的或治疗后结果）的早期乳腺癌患者中易于发挥抗肿瘤作用。目前对于唑来膦酸的最佳剂量和持续时间尚有待于进一步的研究确认,相信随着相关临床试验结果的公布可以提供更充足的证据来支持唑来膦酸在早期乳腺癌的使用。      

Effective inhibition of aromatase inhibitor-associated bone loss by zoledronic acid in postmenopausal women with early breast cancer receiving adjuvant letrozole: ZO-FAST Study results

BACKGROUND: Letrozole is safe and effective in postmenopausal women with estrogen receptor-positive early breast cancer, but long-term aromatase inhibitor use may cause bone loss and increase fracture risk. This study evaluated an immediate or delayed strategy of bone protection therapy with zoledronic acid. METHODS: A total of 1065 patients who were receiving adjuvant letrozole were randomized to immediate-start or delayed-start zoledronic acid (4 mg intravenously biannually for 5 years). The delayed group received zoledronic acid if lumbar spine or total hip T-score decreased below -2.0 or when a nontraumatic fracture occurred. The primary endpoint was change in lumbar spine bone mineral density (BMD) at Month 12. Secondary endpoints included changes in total hip BMD, serum bone turnover markers, and safety at Month 12. RESULTS: Lumbar spine BMD increased from baseline in the immediate arm, while it decreased from baseline in delayed-arm patients. At Month 12, the differences between the groups in lumbar spine and total hip BMD were 5.7% (P < .0001; 95% confidence intervals [CI], 5.2% to 6.1%), and 3.6% (P < .0001; 95% CI, 3.3 to 4.0%), respectively. Both regimens were well tolerated with few serious adverse events. Bone pain was higher in the immediate group, as expected, because some patients experienced acute-phase reactions after zoledronic acid infusion. CONCLUSIONS: At 12 months, immediate zoledronic acid therapy prevented bone loss in postmenopausal women who were receiving adjuvant letrozole.     

Perte osseuse liée aux hormonomodulateurs

The use of hormonal deprivation therapy in the management of breast and prostate cancers is associated with an increased risk of fracture and accelerated bone loss. In women with breast cancer, large adjuvant trials showed that all third-generation AIs (anastrozole, letrozole and exemestane) have been associated with an increased risk of fractures and bone loss. The hypogonadism induced by GnRH agonists increases the risk of osteoporosis; the risk of fracture was shown to be correlated with the duration of therapy and bone loss is maximal in the first year after initiation of the treatment and increases with time. The measurement of bone mineral density is necessary before initiating any hormonal deprivation therapy. The use of bisphosphonates in patients with osteoporosis (defined by a T-score <- ?2.5) and or fracture is useful to prevent bone loss.     

Advances in endocrine treatments for postmenopausal women with metastatic and early breast cancer

For the past 25 years, the estrogen antagonist tamoxifen has been the hormonal treatment of choice for postmenopausal patients with hormone-sensitive metastatic and early breast cancer (EBC). However, tamoxifen is associated with certain tolerability and safety concerns. In addition, the hormonal options after progression are limited, and thus, alternative endocrine treatments have been developed. This review provides a synopsis of the newer alternatives in endocrine therapy of breast cancer: the aromatase inhibitors (AIs) and fulvestrant Faslodex), the estrogen receptor antagonist that downregulates estrogen and progesterone receptors and has no known agonist activity. The third-generation AIs, anastrozole and letrozole, have been shown to be as effective or more effective than megestrol acetate and tamoxifen as second- and first-line therapies for the treatment of postmenopausal patients with metastatic breast cancer, and exemestane has been approved for second-line use. Fulvestrant has been shown to be as effective as anastrozole as second-line therapy for metastatic breast cancer and has been approved in the U.S. for the treatment of postmenopausal women with hormone-receptor-positive metastatic breast cancer following progression on antiestrogen therapy. Anastrozole is the only AI with published clinical trial data and U.S. Food and Drug Administration approval for adjuvant therapy of postmenopausal women with EBC. The 'Arimidex,' Tamoxifen, Alone or in Combination (ATAC) trial, a double-blind, multicenter trial with 9,366 patients, compared tamoxifen with anastrozole, alone and in combination, as adjuvant endocrine treatment for postmenopausal patients with operable, invasive, EBC. The first analysis (at a median follow-up of 33.3 months) showed longer disease-free survival and, in general, better tolerability with anastrozole than with tamoxifen. This pattern was maintained at later analyses with a median follow-up of 47 months for efficacy and 37 months for safety and tolerability. Although longer follow-up is warranted, anastrozole appears to be a well-documented choice of endocrine adjuvant therapy for postmenopausal women with hormone-responsive breast cancer.     

Practical guidance for the management of aromatase inhibitor-associated bone loss

BackgroundRecent studies indicate that women with breast cancer are at increased risk of fracture compared with their age-matched peers. Current treatment guidelines are inadequate for averting fractures in osteopenic women, especially those receiving aromatase inhibitor (AI) therapy. Therefore, we sought to identify clinically relevant risk factors for fracture that can be used to assess overall fracture risk and to provide practical guidance for preventing and treating bone loss in women with breast cancer receiving AI therapy.MethodsSystematic review of pertinent information from published literature and meeting abstracts through December 2007 was carried out to identify factors contributing to fracture risk in women with breast cancer. An evidence-based medicine approach was used to select risk factors that can be used to determine when to initiate bisphosphonate treatment of aromatase inhibitor-associated bone loss (AIBL).ResultsFracture risk factors were chosen from large, well-designed, controlled, population-based trials in postmenopausal women. Evidence from multiple prospective clinical trials in women with breast cancer was used to validate AI therapy as a fracture risk factor. Overall, eight fracture risk factors were validated in women with breast cancer: AI therapy, T-score <-1.5, age >65 years, low body mass index (BMI <20 kg/m²), family history of hip fracture, personal history of fragility fracture after age 50, oral corticosteroid use >6 months, and smoking. Treatment recommendations were derived from randomized clinical trials.ConclusionsThe authors recommend the following for preventing and treating AIBL in women with breast cancer. All patients initiating AI therapy should receive calcium and vitamin D supplements. Any patient initiating or receiving AI therapy with a T-score ≥-2.0 and no additional risk factors should be monitored every 1–2 years for change in risk status and bone mineral density (BMD). Any patient initiating or receiving AI therapy with a T-score <-2.0 should receive bisphosphonate therapy. Any patient initiating or receiving AI therapy with any two of the following risk factors—T-score <-1.5, age >65 years, low BMI (<20 kg/m²), family history of hip fracture, personal history of fragility fracture after age 50, oral corticosteroid use >6 months, and smoking—should receive bisphosphonate therapy. BMD should be monitored every 2 years, and treatment should continue for at least 2 years and possibly for as long as AI therapy is continued. To date, the overwhelming majority of clinical evidence supports zoledronic acid 4 mg every 6 months to prevent bone loss in women at high risk. Although there is a trend towards fewer fractures with zoledronic acid, studies completed to date have not been designed to capture significant differences in fracture rate, and longer follow-up is needed.     

Effects of third-generation aromatase inhibitors on bone

Low oestradiol levels in women are associated with decreased bone mineral density (BMD) and increased fracture risk. The third-generation aromatase inhibitors (AIs; anastrozole, letrozole, and exemestane) are used in the treatment of early and advanced breast cancer and act by substantially reducing oestrogen synthesis in postmenopausal women. However, due to their mechanism of action, there is concern regarding the long-term effects of these agents on bone, particularly when used in the adjuvant setting. In this paper, the currently available data on the effects of the third-generation AIs on markers of bone turnover, BMD, and fracture risk are reviewed, with the emphasis on results in the adjuvant treatment of early breast cancer. These data suggest that both the steroidal (exemestane) and non-steroidal (anastrozole and letrozole) AIs appear to affect bone turnover. Conclusions regarding any clinically relevant differences between these agents are difficult to make, and further data are awaited from long-term adjuvant use of these three agents in ongoing clinical studies. Postmenopausal women are at increased risk of osteoporosis and fracture, and the increasing use of AIs in the adjuvant treatment of postmenopausal breast cancer patients will require appropriate consideration of fracture risk, with the use of anti-osteoporotic therapies, if necessary.     

Evolving role of bisphosphonates in women undergoing treatment for localized and advanced breast cancer

Breast cancer commonly metastasizes to bone, producing hypercalcemia, pathologic fractures, spinal compression, and pain that increase morbidity and affect the patient's mobility and quality of life. The use of bisphosphonates like pamidronate and zoledronic acid inhibits osteolytic activity caused by bone metastases. The use of bisphosphonates to prevent bone loss and preserve bone health in the adjuvant setting in women with breast cancer undergoing hormonal therapy with aromatase inhibitors or ovarian suppression is being actively investigated. Interestingly, clodronate, an oral bisphosphonate, has been shown in 2 trials to decrease the risk of recurrence in women with early-stage breast cancer, suggesting a direct or indirect antitumor effect of bisphosphonates. Trials to confirm the antitumor effects of bisphosphonates are currently ongoing. Prolonged intravenous bisphosphonate use has been associated with a rare risk of osteonecrosis of the jaw. Recommendations for management of this condition are discussed.     

The role of aromatase inhibitors in early breast cancer

Opinion statement The role of hormonal therapy for the treatment of patients with early stage breast cancer has been evaluated in many studies. The results of these studies establish tamoxifen as the gold standard of hormonal therapy for the adjuvant treatment of hormone receptorpositive invasive breast cancer in pre- and postmenopausal women. Studies show tamoxifen reduces the risk of invasive breast cancer in women at increased risk for the disease, including women with ductal carcinoma in situ. Tamoxifen has adverse effects such as hot flashes, increased risk of uterine cancer in postmenopausal women, and rare occurrence of thromboembolic disease. Despite the multiple therapeutic roles of tamoxifen, alternatives are needed. Aromatase inhibitors (AI) are drugs with antiestrogenic activity. AIs function by inhibiting the peripheral conversion of adrenally synthesized androstenedione to estradiol through inhibition of the aromatase enzyme. AIs do not suppress estradiol synthesis by the ovary adequately. Therefore, AIs are effective in reducing circulating estradiol levels in postmenopausal women, but not premenopausal women. Selective nonsteroidal AIs, including anastrozole (Arimidex; AstraZeneca, Wilmington, DE) and letrozole (Femara; Novartis, East Hanover, NJ), and the steroidal AI exemestane (Aromasin; Pharmacia, Peapack, NJ) have been associated with increased specificity and improved therapeutic index compared to nonselective AIs such as aminoglutethamide. Nonsteroidal and steroidal AIs have demonstrated to be superior to megestrol acetate in second-line therapy of postmenopausal women with metastatic breast cancer, and selective nonsteroidal AIs have shown to be superior to tamoxifen in first-line therapy of postmenopausal women with metastatic breast cancer. The ATAC (Arimidex, tamoxifen, alone, or in combination) trial is the only published randomized trial comparing the efficacy of an AI to tamoxifen for the adjuvant treatment of women with early breast cancer. This large study showed that at a median follow-up time of 33 months, anastrozole alone results in significant improvement in disease-free survival rates, reduction in contralateral breast cancers, and increased tolerability, compared to tamoxifen in postmenopausal women. Although the long-term effects of AIs are not known, the early positive results of the ATAC trial led to the approval of anastrozole by the US Food and Drug Administration for use as adjuvant hormonal therapy for postmenopausal women with hormone receptor-positive invasive breast cancer. Thus, there is an alternative to tamoxifen for postmenopausal women with relative/absolute contraindications to tamoxifen use or patients who choose not to take tamoxifen because of its side-effect profile. New AIs may challenge the position of tamoxifen as the gold standard for the treatment of early stage breast cancer in postmenopausal women.     

Adjuvant aromatase inhibitors following tamoxifen for early-stage breast cancer in postmenopausal women: what do we really know?

Adjuvant hormonal therapy in the treatment of women with early-stage, hormone receptor (HR)-positive breast cancer is now considered the standard of care. Adjuvant tamoxifen decreases the risk of breast cancer recurrence and death in women with early-stage breast cancer when taken for 5 years. The benefits of tamoxifen are counterbalanced by toxicities including an increased risk of endometrial cancer and thromboembolic events. The selective aromatase inhibitors (AIs)--including anastrozole, letrozole, and exemestane--are challenging the role of tamoxifen as the adjuvant hormonal therapy of choice in postmenopausal women. Results of the Arimidex and Tamoxifen Alone or in Combination trial favor the use of anastrozole over tamoxifen as initial adjuvant hormonal therapy, with improvement in disease-free survival (DFS) and a favorable toxicity profile. The results of 2 large adjuvant trials using AIs sequentially with tamoxifen in postmenopausal women with early-stage, HR-positive breast cancer have been reported. The MA-17 study randomized women to placebo or letrozole for 5 years after completion of 4.5-6 years of initial tamoxifen. The Intergroup Exemestane Study (IES) randomized women following 2-3 years of adjuvant tamoxifen to continue to receive tamoxifen or switch to exemestane for a total of 5 years of adjuvant hormonal therapy. The MA-17 and IES trials demonstrated superior DFS with the AI and corroborated the smaller GROCTA-4B and Italian Tamoxifen Arimidex trials, which studied sequential therapy with aminoglutethamide or anastrozole. There is now substantial medical evidence supporting the use of AIs in postmenopausal women with early-stage, HR-positive breast cancer.