Current management of treatment-induced bone loss in women with breast cancer treated in the United Kingdom

A polygenic score associated with fracture risk in breast cancer patients treated with aromatase inhibitors

Identifying women at high risk of osteoporotic fracture from aromatase inhibitor (AI) therapy for breast cancer is largely based on known risk factors for healthy postmenopausal women, which might not accurately reflect the risk in breast cancer patients post-AI therapy. To determine whether a polygenic score associated with fracture in healthy women is also significant in women treated with AIs for breast cancer, we used data from a prospective observational cohort of 2152 women diagnosed with hormonal receptor positive breast cancer treated with AIs as the initial endocrine therapy and examined a polygenic score of heel quantitative ultrasound speed of sound (gSOS) in relation to incident osteoporotic fracture after AI therapy during a median 6.1 years of follow up after AI initiation. In multivariable models, patients with the second and third highest tertiles (T) versus the lowest tertile of gSOS had significantly lower risk of fracture (T2: adjusted HR = 0.61, 95% CI: 0.46-0.80; T3: adjusted HR = 0.53, 95% CI: 0.40-0.70). The lower risk of fracture in patients with the highest tertile of gSOS remained significant after further adjustment for BMD at the hip (T3: adjusted HR = 0.62, 95% CI: 0.42-0.91). In conclusion, our analysis showed gSOS as a novel genetic predictor for fracture risk independent of BMD among breast cancer patients treated with AIs. Future studies are warranted to evaluate the performance of incorporating gSOS in prediction models for the risk of AI-related fracture in breast cancer patients.

Bone health in breast cancer

Early breast cancer is among the most common cancers worldwide. Recent advances continue to improve outcomes and increase long-term survivorship. However, therapeutic modalities are deleterious for patients' bone health. While antiresorptive therapy may partially negate this, consequent reduction in rates of fragility fractures remains unproven. Selective prescription of bisphosphonates or denosumab may be an amicable middle ground. Recent evidence also suggests a possible role of osteoclast inhibitors as adjuvant therapy, but the evidence is modest at best. In this narrative clinical review, we explore the impact of various adjuvant modalities on bone mineral density and fragility fracture rates of early breast cancer survivors. We also review optimal patient selection for antiresorptive agents, their impact on rates of fragility fractures, and the possible role of these agents as adjuvant therapy.

Skeletal manifestations of treatment of breast cancer

Breast cancer and osteoporosis are common diagnoses in women. Breast cancer survival has improved due to earlier detection and improved treatments. As most breast cancers are estrogen receptor positive, treatment is often aimed at altering the hormonal environment. Both pre and postmenopausal women undergoing these therapies are at risk for bone loss. The patient's health care team ought to have an awareness of the potential for breast cancer treatments to accelerate bone loss. Women with early stage breast cancer are treated with curative intent and, therefore, maintaining bone health is important and is part of the survivorship care to ensure an optimal quality of life.

Optimizing bone health and minimizing skeletal morbidity in men with prostate cancer

Maintaining bone health is important in the management of men with prostate cancer. Patients receiving androgen deprivation therapy are at increased risk for treatment-related osteoporosis, and patients with bone metastases are at increased risk for skeletal morbidity related to debilitating skeletal-related events (SREs). Optimizing bone health in these patients includes lifestyle modifications, calcium/vitamin D supplementation, and osteoclast-targeted agents in select high-risk patients. No agent is approved for the prevention of bone metastases. Novel systemic agents have shown a beneficial effect bone by directly affecting tumor growth. Integration of these anticancer agents with osteoclast-targeted agents warrants further investigation.

Vitamin D status at breast cancer diagnosis: correlation with tumor characteristics, disease outcome, and genetic determinants of vitamin D insufficiency

We correlated serum 25-hydroxyvitamin D(3) (25OHD) levels with tumor characteristics and clinical disease outcome in breast cancer patients and assessed the impact of genetic determinants of vitamin D insufficiency. We collected serum from 1800 early breast cancer patients at diagnosis, measured 25OHD by radioimmunoassay (RIA), and determined genetic variants in vitamin D-related genes by Sequenom. Multivariable regression models were used to correlate 25OHD levels with tumor characteristics. Cox proportional hazard models were used to assess overall survival (OS), disease-specific survival (DSS), and disease-free interval (DFI). Lower 25OHD serum levels significantly correlated with larger tumor size at diagnosis (P = 0.0063) but not with lymph node invasion, receptor status, or tumor grade. Genetic variants in 25-hydroxylase (CYP2R1) and vitamin D-binding (DBP) protein significantly determined serum 25OHD levels but did not affect the observed association between serum 25OHD and tumor size. High serum 25OHD (>30 ng/mL) at diagnosis significantly correlated with improved OS (P = 0.0101) and DSS (P = 0.0192) and additionally had a modest effect on DFI, which only became apparent after at least 3 years of follow-up. When considering menopausal status, serum 25OHD had a strong impact on breast cancer-specific outcome in postmenopausal patients [hazards ratios for 25OHD >30 ng/mL versus ≤30 ng/mL were 0.15 (P = 0.0097) and 0.43 (P = 0.0172) for DSS and DFI, respectively], whereas no association could be demonstrated in premenopausal patients. In conclusion, high vitamin D levels at early breast cancer diagnosis correlate with lower tumor size and better OS, and improve breast cancer-specific outcome, especially in postmenopausal patients.

Prevention of osteoporosis as a consequence of aromatase inhibitor therapy in postmenopausal women with early breast cancer: rationale and design of a randomized controlled trial

BACKGROUND

Aromatase inhibitors (AIs) have improved the prognosis for breast cancer survivors and are now standard of care for postmenopausal women with hormone receptor positive early stage breast cancer. One side-effect, however, is a decrease in bone mineral density (BMD) and increased fracture risk. Since hormone replacement therapy (HRT) is contraindicated in these women, one prevention option is exercise combined with vitamin D and calcium. The effect of this intervention on drug-induced osteoporosis is unknown.

METHODS

A single-blind randomized controlled trial will be undertaken to test the hypothesis that exercise combined with vitamin D and calcium can prevent the decrease in BMD associated with the use of AIs. Sixty postmenopausal women prescribed an AI for the treatment of breast cancer will be randomized into either an exercise or control group. Participants randomized to the exercise group will undertake a 12-month gym-based exercise program, 3 times per week involving resistance and impact training. Participants in the control group will be advised on the benefits of exercise for preventing osteoporosis, but not prescribed exercise. Both groups will receive vitamin D and calcium supplements. The primary outcome will be total hip bone mineral density measured via dual energy X-ray absorptiometry (DXA). Study outcomes will be compared between groups at baseline, 6months and 12months.

SUMMARY

This study will investigate the effect of exercise in combination with vitamin D and calcium on prevention of drug-induced osteoporosis in postmenopausal women prescribed AIs for the treatment of breast cancer.

Effects of a structured weight-bearing exercise program on bone metabolism among breast cancer survivors: a feasibility trial

PURPOSE

Treatments for breast cancer, specifically hormonal therapy, accelerate bone loss (BL) among breast cancer survivors, leading to osteoporosis and an increase in fracture risk. Tai Chi Chuan (TCC) is a moderate form of weight-bearing exercise, equivalent to walking, and it has been shown to improve aerobic capacity and strength among breast cancer survivors and might also be effective in slowing bone loss in breast cancer survivors. This pilot study compared the influence of TCC with that of standard support therapy (ST; exercise control) on BL biomarkers among breast cancer survivors.

PATIENTS AND METHODS

Randomly assigned breast cancer survivors (N = 16; median age, 53 years; < 30 months after treatment) completed 12 weeks (3 times per week, 60 minutes per session) of TCC or ST. Serum levels of N-telopeptides of type I collagen (NTx), a marker of bone resorption, and bone-specific alkaline phosphatase (BSAP), a marker of bone formation, were determined according to enzyme-linked immunosorbent assay at baseline and after the intervention.

RESULTS

Using analysis of covariance, survivors in the TCC group experienced a greater increase in levels of bone formation (BSAP [microg/L]: before, 8.3; after, 10.2; change, 1.9 microg/L and 22.4%), compared with survivors in ST (BSAP [microg/L]: before, 7.6; after, 8.1; change, 0.5 microg/L [6.3%]). Survivors in the TCC group also experienced a significant decrease in bone resorption (NTx [nanomoles bone collagen equivalent; nmBCE]: before, 17.6; after, 11.1; change, -6.5 nmBCE; -36.9%), whereas women in the ST group did not (NTx [nmBCE]: before, 20.8; after, 18.8; change, -2.0 nmBCE; -9.6%).

CONCLUSION

This pilot study suggests that weight-bearing exercise exerts positive effects on BL, through increased bone formation and decreased bone resorption. Further examinations of the influence of TCC on bone health are warranted.