Guidelines for Osteoprotection in Breast Cancer Patients on an Aromatase Inhibitor

Modeling of Mouse Experiments Suggests that Optimal Anti-Hormonal Treatment for Breast Cancer is Diet-Dependent

Estrogen receptor positive breast cancer is frequently treated with anti-hormonal treatment such as aromatase inhibitors (AI). Interestingly, a high body mass index has been shown to have a negative impact on AI efficacy, most likely due to disturbances in steroid metabolism and adipokine production. Here, we propose a mathematical model based on a system of ordinary differential equations to investigate the effect of high-fat diet on tumor growth. We inform the model with data from mouse experiments, where the animals are fed with high-fat or control (normal) diet. By incorporating AI treatment with drug resistance into the model and by solving optimal control problems we found differential responses for control and high-fat diet. To the best of our knowledge, this is the first attempt to model optimal anti-hormonal treatment for breast cancer in the presence of drug resistance. Our results underline the importance of considering high-fat diet and obesity as factors influencing clinical outcomes during anti-hormonal therapies in breast cancer patients.

Long-term effect of aromatase inhibitors on bone microarchitecture and macroarchitecture in non-osteoporotic postmenopausal women with breast cancer

In non-osteoporotic postmenopausal women with breast cancer, aromatase inhibitors (AIs) negatively affected bone mineral density (BMD), lumbar spine trabecular bone score (TBS) as a bone microarchitecture index, and hip geometry as a bone macroarchitecture index.

INTRODUCTION

AIs increase the risk of fracture in patients with breast cancer. Therefore, we aimed to evaluate the long-term skeletal effects of AIs in postmenopausal women with primary breast cancer.

METHODS

We performed a retrospective longitudinal observational study in non-osteoporotic patients with breast cancer who were treated with AIs for ≥3 years (T-score >-2.5). Patients with previous anti-osteoporosis treatment or those who were given bisphosphonate during AI treatment were excluded from the analysis. We serially assessed BMD, lumbar spine TBS, and hip geometry using dual-energy X-ray absorptiometry.

RESULTS

BMD significantly decreased from baseline to 5 years at the lumbar spine (-6.15%), femur neck (-7.12%), and total hip (-6.35%). Lumbar spine TBS also significantly decreased from baseline to 5 years (-2.12%); this change remained significant after adjusting for lumbar spine BMD. The annual loss of lumbar spine BMD and TBS slowed after 3 and 1 year of treatment, respectively, although there was a relatively constant loss of BMD at the femur neck and total hip for up to 4 years. The cross-sectional area, cross-sectional moment of inertia, minimal neck width, femur strength index, and section modulus significantly decreased, although the buckling ratio increased over the treatment period (all P < 0.001); these changes were independent of total hip BMD.

CONCLUSIONS

Long-term adjuvant AI treatment negatively influenced bone quality in addition to BMD in patients with breast cancer. This study suggests that early monitoring and management are needed in non-osteoporotic patients with breast cancer who are starting AIs.

Role of bone-anabolic agents in the treatment of breast cancer bone metastases

Skeletal metastases are an incurable complication afflicting the majority of patients who die from advanced breast cancer. They are most often osteolytic, characterized by net bone destruction and suppressed new bone formation. Life expectancy from first diagnosis of breast cancer bone metastases is several years, during which time skeletal-related events - including pain, fracture, hypercalcemia, and spinal cord compression - significantly degrade quality of life. The bone marrow niche can also confer hormonal and chemo-resistance. Most treatments for skeletal metastases target bone-destroying osteoclasts and are palliative. Recent results from the Breast cancer trials of Oral Everolimus-2 trial suggest that agents such as the mammalian target of rapamycin inhibitor everolimus may have efficacy against breast cancer bone metastases in part via stimulating osteoblasts as well as by inhibiting tumor growth. Selective estrogen receptor modulators similarly inhibit growth of estrogen receptor-positive breast cancers while having positive effects on the skeleton. This review discusses the future role of bone-anabolic agents for the specific treatment of osteolytic breast cancer metastases. Agents with both anti-tumor and bone-anabolic actions have been tested in the setting of multiple myeloma, a hematological malignancy that causes severe osteolytic bone loss and suppression of osteoblastic new bone formation. Stimulation of osteoblast activity inhibits multiple myeloma growth - a strategy that might decrease breast cancer burden in osteolytic bone metastases. Proteasome inhibitors (bortezomib and carfilzomib) inhibit the growth of myeloma directly and are anabolic for bone. Drugs with limited anti-tumor activity but which are anabolic for bone include intermittent parathyroid hormone and antibodies that neutralize the WNT inhibitors DKK1 and sclerostin, as well as the activin A blocker sotatercept and the osteoporosis drug strontium ranelate. Transforming growth factor-beta inhibitors have little tumor antiproliferative activity but block breast cancer production of osteolytic factors and are also anabolic for bone. Some of these treatments are already in clinical trials. This review provides an overview of agents with bone-anabolic properties, which may have utility in the treatment of breast cancer metastatic to the skeleton.

Prevention of bone loss with risedronate in breast cancer survivors: a randomized, controlled clinical trial

In postmenopausal women with low bone mass and hormone-receptor-positive breast cancer on an aromatase inhibitor, risedronate maintained skeletal health assessed by bone density and turnover markers. Women with the greatest decreases in bone turnover markers at 12 months had the greatest increases in bone density at 24 months.

INTRODUCTION

Aromatase inhibitors (AIs), adjuvant endocrine therapy for postmenopausal women with hormone-receptor-positive breast cancer, are associated with bone loss and fractures. Our objectives were to determine if (1) oral bisphosphonate therapy can prevent bone loss in women on an AI and (2) early changes in bone turnover markers (BTM) can predict later changes in bone mineral density (BMD).

METHODS

We conducted a 2-year double-blind, placebo-controlled, randomized trial in 109 postmenopausal women with low bone mass on an AI (anastrozole, letrozole, or exemestane) for hormone-receptor-positive breast cancer. Participants were randomized to once weekly risedronate 35 mg or placebo, and all received calcium plus vitamin D. The main outcome measures included BMD, BTM [carboxy-terminal collagen crosslinks (CTX) and N-terminal propeptide of type 1 procollagen (P1NP)], and safety.

RESULTS

Eighty-seven percent completed 24 months. BMD increased more in the active treatment group compared to placebo with an adjusted difference at 24 months of 3.9 ± 0.7 percentage points at the spine and 3.2 ± 0.5 percentage points at the hip (both p < 0.05). The adjusted difference between the active treatment and placebo groups were 0.09 ± 0.04 nmol/LBCE for CTX and 23.3 ± 4.8 μg/mL for P1NP (both p < 0.05). Women with greater 12-month decreases in CTX and P1NP in the active treatment group had a greater 24-month increase in spinal BMD (p < 0.05). The oral therapy was safe and well tolerated.

CONCLUSION

In postmenopausal women with low bone mass and breast cancer on an AI, the oral bisphosphonate risedronate maintained skeletal health.

Cancer-associated bone disease

Bone is commonly affected in cancer. Cancer-induced bone disease results from the primary disease, or from therapies against the primary condition, causing bone fragility. Bone-modifying agents, such as bisphosphonates and denosumab, are efficacious in preventing and delaying cancer-related bone disease. With evidence-based care pathways, guidelines assist physicians in clinical decision-making. Of the 57 million deaths in 2008 worldwide, almost two thirds were due to non-communicable diseases, led by cardiovascular diseases and cancers. Bone is a commonly affected organ in cancer, and although the incidence of metastatic bone disease is not well defined, it is estimated that around half of patients who die from cancer in the USA each year have bone involvement. Furthermore, cancer-induced bone disease can result from the primary disease itself, either due to circulating bone resorbing substances or metastatic bone disease, such as commonly occurs with breast, lung and prostate cancer, or from therapies administered to treat the primary condition thus causing bone loss and fractures. Treatment-induced osteoporosis may occur in the setting of glucocorticoid therapy or oestrogen deprivation therapy, chemotherapy-induced ovarian failure and androgen deprivation therapy. Tumour skeletal-related events include pathologic fractures, spinal cord compression, surgery and radiotherapy to bone and may or may not include hypercalcaemia of malignancy while skeletal complication refers to pain and other symptoms. Some evidence demonstrates the efficacy of various interventions including bone-modifying agents, such as bisphosphonates and denosumab, in preventing or delaying cancer-related bone disease. The latter includes treatment of patients with metastatic skeletal lesions in general, adjuvant treatment of breast and prostate cancer in particular, and the prevention of cancer-associated bone disease. This has led to the development of guidelines by several societies and working groups to assist physicians in clinical decision making, providing them with evidence-based care pathways to prevent skeletal-related events and bone loss. The goal of this paper is to put forth an IOF position paper addressing bone diseases and cancer and summarizing the position papers of other organizations.

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

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