Optimizing bisphosphonate therapy in patients with breast cancer on endocrine therapy

Adverse events and bone health during anastrozole therapy in postmenopausal Japanese breast cancer patients

BACKGROUND

Although anastrozole (ANA), an aromatase inhibitor (AI), has been widely used for breast cancer patients; adverse events during ANA therapy in Japanese patients have not been reported.

METHODS

The study included 656 postmenopausal breast cancer patients receiving ANA as postoperative adjuvant therapy in our hospital. Adverse events during ANA therapy, such as musculoskeletal effects and cerebro- and cardiovascular accidents, were investigated over a 5-year period. The percentage changes in lumbar (L2-4) spine bone mineral density (BMD) were determined in 71 patients receiving ANA alone and 26 patients receiving bisphosphonate in combination with ANA for 7-24 months.

RESULTS

The follow-up period ranged from 6 to 60 months (median 23 months). Joint pain, the most common adverse event, was observed in 3.6% (24/656) of the patients. Cerebral infarctions occurred in 0.3% (2/656) of the patients, and no cardiovascular accidents occurred. Bone fractures occurred in nine patients receiving ANA alone. The mean age and BMD of the nine patients were 67.6 years and 71.8% (compared to the young adult mean BMD), respectively. Accumulated and annual fracture rates were 1.3 and 0.8%, respectively. A decrease in BMD was observed in 62.0% (44/71) of the ANA group compared to 26.9% (7/26) of the combination bisphosphonate group (P < 0.01).

CONCLUSION

Incidence of adverse events during AI therapy in this Japanese postmenopausal population appears to be lower than that of the ATAC trial. The incidence of bone fractures during AI therapy is lower in Japan, and the addition of bisphosphonates enhances bone health. We should perform a prospective trial in the future to investigate the precise risk of bone fractures in Japanese patients.

Treatment delay of bone tumours, compilation of a sociodemographic risk profile: a retrospective study

BACKGROUND

Bone tumours are comparatively rare tumours and delays in diagnosis and treatment are common. The purpose of this study was to analyse sociodemographic risk factors for bone tumour patients in order to identify those at risk of prolonged patients delay (time span from first symptoms to consultation), professional delay (from consultation to treatment) or symptom interval (from first symptoms to treatment). Understanding these relationships might enable us to shorten time to diagnosis and therapy.

METHODS

We carried out a retrospective analysis of 265 patients with bone tumours documenting sociodemographic factors, patient delay, professional delay and symptom interval. A multivariate explorative Cox model was performed for each delay.

RESULTS

Female gender was associated with a prolonged patient delay. Age under 30 years and rural living predisposes to a prolonged professional delay and symptom interval.

CONCLUSION

Early diagnosis and prompt treatment are required for successful management of most bone tumour patients. We succeeded in identifying the histology independent risk factors of age under 30 years and rural habitation for treatment delay in bone tumour patients. Knowing about the existence of these risk groups age under 30 years and female gender could help the physician to diagnose bone tumours earlier. The causes for the treatment delays of patients living in a rural area have to be investigated further. If the delay initiates in the lower education of rural general physicians, further training about bone tumours might advance early detection. Hence the outcome of patients with bone tumours could be improved.

Aromatase inhibitor-induced bone mineral loss and its prevention by bisphosphonate administration in postmenopausal breast cancer patients

AIM

To investigate aromatase inhibitor-induced bone mineral loss and its prevention by bisphosphonate administration in postmenopausal breast cancer patients.

METHODS

Subjects were 17 postmenopausal breast cancer patients (mean age, 63.3 +/- 9.9 years) receiving non-steroidal aromatase inhibitor (AI; anastrozole, 1 mg daily) only and 10 such patients (mean age, 65.0 +/- 5.1 years) receiving AI + bisphosphonate (risedronate sodium, 2.5 mg daily) for 6 months. All of the subjects had undergone surgical resection and had positive estrogen receptor tumor status. Age, age at menopause, years since menopause, height, weight, and body mass index (Wt/Ht(2)) were recorded. Lumbar spine (L2-4) bone mineral density (BMD), T-, and Z-scores were assessed on dual-energy X-ray absorptiometry before and after therapy.

RESULTS

In the AI-only group BMD, T-, and Z-scores significantly decreased from the baseline during the 6-month therapy period (P < 0.05). Mean decreases in L2-4 BMD and Z-score were 2.5% and 3.0%, respectively. In the AI + bisphosphonate group, however, BMD, T-, and Z-scores significantly increased from the baseline values (P < 0.01). Mean increases in L2-4 BMD and Z-score were 4.5% and 3.3%, respectively.

CONCLUSION

AI carries a potential risk of bone mineral loss despite the short therapy duration. Bisphosphonate has a preventive effect on this loss.

Biology of bone metastases: causes and consequences

Breast cancer is a highly osteotropic neoplasm, and as many as 75% of patients with metastatic disease will have involvement of the bony skeleton. On radiologic examination, these metastases are predominantly osteolytic but can be osteoblastic or mixed. The mechanisms by which metastases are formed are complex, involving many steps that include angiogenesis, invasion, and proliferation in the bone microenvironment. Tumor cells in the bone microenvironment produce a large number of cytokines that stimulate osteoclastic activity. Increased osteoclastic activity, in turn, leads to production of a variety of lymphokines and growth factors that can increase tumor cell proliferation. Thus, a cytokine network is established, which results in an imbalance of the processes of bone formation and bone resorption. As tumor burden in bone increases, osteoclast-mediated bone resorption is accelerated, resulting in loss of bone strength, fractures, pain, and other morbidities. Tumor cells metastatic to bone can also secrete growth factors, leading to increased osteoblastic activity. Osteoblasts lay down an excess of new bone that is structurally weak. There is considerable crosstalk between osteoclasts, osteoblasts, macrophages, and other cellular elements within the bone environment. The increasing understanding of the biology of bone metastases has opened the door to improved management of this important clinical problem. Current treatment strategies include approaches to reduce tumor burden and developing treatments that directly inhibit osteoclast function. The bisphosphonates are a class of drugs that inhibit osteoclast recruitment and function. Several highly potent bisphosphonates are now available for clinical use and represent an important adjunct in the management of bone metastases from breast cancer, multiple myeloma, and several other types of malignancies. Some newer therapeutic approaches include agents designed to inhibit the osteoclast-osteoblast signaling interactions or alter processes of adhesion and invasion.

Appraising Adjuvant Aromatase Inhibitor Therapy

Tamoxifen, once the gold standard adjuvant endocrine therapy for early breast cancer, is being challenged by third-generation aromatase inhibitors (AIs) that have demonstrated improved disease-free survival in a variety of adjuvant settings for early breast cancer. Tamoxifen and AIs have different safety profiles, which should allow physicians to begin to individualize treatment based on a patient's comorbidities and risk factors. Because of its properties as a partial estrogen agonist, tamoxifen has a positive effect on serum lipids and may confer a cardioprotective benefit, as well as a beneficial effect on bone health. However, tamoxifen increases the risk for endometrial cancer and cerebrovascular/thromboembolic events. In comparison, the major side effect of AIs is increased bone loss, which may heighten the risk for osteoporotic fractures and bone pain. Because of their superior efficacy and manageable side effects, AIs are a cost-effective alternative to tamoxifen, and clinical guidelines now embrace AIs as appropriate adjuvant therapy for hormone-sensitive early breast cancer. The anticipated results of ongoing trials will provide further insights into the long-term safety and application of AI therapy in the adjuvant setting.

Management of Cancer-Treatment–Induced Bone Loss in Postmenopausal Women Undergoing Adjuvant Breast Cancer Therapy: A Z-FAST Update

The prevention of cancer-treatment-induced bone loss (CTIBL) in long-term adjuvant breast cancer therapy is a high priority. Postmenopausal women with cancer, already at increased risk of bone loss because of age-related estrogen deficiency, face accelerated bone loss with the use of estrogen-depleting therapies such as third-generation aromatase inhibitors (AIs). Although effective in reducing cancer recurrence rates in the adjuvant setting, AIs are associated with bone loss and an increased risk of fractures. Bisphosphonates, which act by inhibiting osteoclastic bone resorption, have been shown to increase bone mineral density (BMD) and reduce fracture risk in postmenopausal women with established osteoporosis. Furthermore, the potent bisphosphonate zoledronic acid has been shown to be efficacious in reducing bone loss in premenopausal women receiving combination adjuvant hormone therapy (goserelin, a gonadotropin-releasing hormone agonist, plus either an AI or tamoxifen). The use of zoledronic acid to prevent CTIBL in postmenopausal women receiving adjuvant AI therapy with letrozole is currently being investigated in the Zometa/Femara Adjuvant Synergy Trial (Z-FAST). Postmenopausal women with stage I-IIIa estrogen-receptor-positive and/or progesterone-receptor-positive breast cancer starting letrozole are randomized to receive either upfront zoledronic acid or delayed zoledronic acid. At 6 months, assessable women in the upfront group showed a mean increase of 1.55% in lumbar spine (L1 - L4) BMD, compared with a mean decrease of 1.78% in women in the delayed group, resulting in a difference of 3.33% between groups; moreover, women in the former group showed a mean increase of 1.02% in total hip BMD, compared with a mean decrease of 1.40% in those in the latter group, resulting in a significant difference of 2.42% between groups (P <.001). Thus, the Z-FAST BMD results show that upfront zoledronic acid prevents CTIBL in postmenopausal women receiving adjuvant letrozole therapy for early breast cancer. Combining the anticancer efficacy of letrozole with the bone-protective effect of zoledronic acid may be a successful treatment in this setting.

Improving bone health in patients with early breast cancer by adding bisphosphonates to letrozole: The Z-ZO-E-ZO-FAST program

Women undergoing treatment for breast cancer often have a number of pre-existing risk factors for bone loss, including existing or induced postmenopausal status. Long-term anticancer treatments may further augment this risk, inducing further bone-loss, increasing the incidence of bone fractures, associated morbidity and mortality, and healthcare costs. Long-term treatment with third-generation antiaromatase agents (AAAs) is used more and more instead of or after the selective estrogen-receptor modulator tamoxifen for the adjuvant treatment of postmenopausal women with breast cancer. These AAAs include anastrozole, letrozole, and exemestane, and all are superior to tamoxifen in both efficacy and safety. In particular, they reduce the incidence of serious adverse events such as thromboembolism and endometrial cancer that are associated with tamoxifen treatment. On the other hand, the AAAs lead to profound estrogen depletion and appear to have a pronounced effect on bone mineral density (BMD), and a significantly higher incidence of osteoporosis/osteopenia and bone fracture has been reported in some trials. Bisphosphonate therapies, including zoledronic acid (ZA), have emerged as a promising means of reducing bone loss associated with antiaromatase therapy. Several large, randomized, multicenter trials are underway to determine whether upfront or delayed ZA therapy can decrease BMD losses in patients undergoing treatment with the antiaromatase agent letrozole (Z-FAST; ZO-FAST, and E-ZO-FAST), and early results from the Zometa-Femara adjuvant synergy trial (Z-FAST) trial indicate a significant benefit of upfront ZA therapy compared with delayed ZA therapy. Forthcoming results from all these trials should determine whether ZA could be used to improve bone heath in women undergoing adjuvant therapy with AAAs for breast cancer.

Breast cancer metastasis to bone: mechanisms of osteolysis and implications for therapy

The most common skeletal complication of breast cancer is osteolytic bone metastasis. Bone metastases are present in 80% of patients with advanced disease and cause significant morbidity. They are most often osteolytic, but can be osteoblastic or mixed. Tumor cells, osteoblasts, osteoclasts and bone matrix are the four components of a vicious cycle necessary for the initiation and development of bone metastases. Tumor cell gene expression is modified by interaction with bone-derived factors. For example, parathyroid hormone related protein (PTHrP), a tumor cell factor, is upregulated by bone-derived transforming growth factor beta (TGFbeta). Tumor cell factors, in turn, act upon bone cells to cause dysregulated bone destruction and formation. PTHrP increases osteoblast expression of RANK (receptor activator of NFkappaB) ligand which, in turn, activates osteoclasts. PTHrP-independent osteolytic factors, such as interleukin [IL]-11 and IL-8, also contribute to the vicious cycle. Other tumor-bone interactions, such as stimulation of tumor-homing through the CXCR4 chemokine receptor by its bone-derived ligand stromal-derived factor-1 (SDF-1), may be responsible for the site-specific predilection of breast cancer for bone. These factors and their roles in fueling the vicious cycle may identify novel targets for therapies to prevent metastasis.