Bone Health in Patients with Breast Cancer: Recommendations from an Evidence-Based Canadian Guideline

Challenges in Preventing Bone Loss Induced by Aromatase Inhibitors

CONTEXT

Aromatase inhibitors have become a mainstay in the adjuvant treatment regimen in postmenopausal women with hormone receptor-positive breast cancer. While many of these patients have an excellent long-term prognosis, adverse effects on bone represent an emerging complication of aromatase inhibitor treatment, resulting in substantial bone loss and fragility fractures. Treatment approaches to prevent aromatase inhibitor-induced bone loss typically consist of an antiresorptive approach with bisphosphonates or the RANKL antibody denosumab. However, different guidelines vary with respect to treatment thresholds, duration, and dosing. The choice of antiresorptive regime is further complicated by comorbidities and potential disease-modifying effects of individual agents.

OBJECTIVE

This review summarizes the evidence of how aromatase inhibitors affect bone health and provides an update of clinical approaches to preserve bone strength in affected women. (J Clin Endocrinol Metab XX: 0-0, 2020).

Aromatase inhibitors attenuate the effect of alendronate in women with breast cancer

INTRODUCTION

Aromatase inhibitors are known to accelerate bone loss in patients with breast cancer. However, how much AIs affect the efficacy of antiresorptive agents has not been studied. The study aimed to compare the effect of alendronate on bone mineral density (BMD) between patients with and without AI treatment.

MATERIALS AND METHODS

In this retrospective study, 90 postmenopausal women with early breast cancer who were being treated with both AI and alendronate 70 mg weekly (ALN + AI), and 90 age- and body mass index (BMI)-matched patients who were only taking alendronate (ALN-only) were analyzed. BMD and bone turnover markers (BTMs) were assessed at the baseline and 12 months.

RESULTS

The mean age was 63 years. At baseline, the ALN-only group had lower lumbar spine (LS), femur neck (FN), and total hip (TH) BMD than ALN + AI group. After 1-year of alendronate treatment, the LS and FN BMD were improved more in the ALN-only group than those in the ALN + AI group after adjustments for age, BMI, baseline BMD, diabetes, hypertension, renal function, and previous fracture history [LS BMD: 6.2% (3.1%; 9.2%) in ALN-only, 3.5% (-0.5%; 6.5%) in ALN + AI, p = 0.001; FN BMD: 2.5% (0.3%; 5.7%) in ALN-only, 0.9% (- 1.8%; 3.6%) in ALD + AI, p = 0.032]. BTMs were significantly decreased in both groups, but the changes between groups were similar.

CONCLUSION

The effect of alendronate on the LS and FN BMD was attenuated in postmenopausal women who were taking AI compared to those who were not on AI.

The effects of adjuvant endocrine therapy on bone health in women with breast cancer

In women with oestrogen receptor (ER)-positive early breast cancer, oestradiol is important for breast cancer development and progression. Endocrine therapy prevents the deleterious effects of oestradiol in breast tissue by systemically depleting oestradiol concentration (aromatase inhibitors) or preventing its local action in breast tissue (selective oestrogen receptor modulators i.e. tamoxifen), thereby improving oncological outcomes. Use of aromatase inhibitors in postmenopausal women and ovarian function suppression with either tamoxifen or aromatase inhibition in premenopausal women, consequent to systemic oestradiol depletion, exerts detrimental effects on skeletal health. The oestradiol-deficient state causes increased bone remodelling and a negative bone balance. This results in bone loss, microstructural deterioration and bone fragility predisposing to fractures. Similar effects are also seen with tamoxifen in premenopausal women. In contrast, use of tamoxifen in postmenopausal women appears to exert protective effects on bone but studies on fracture risk are inconclusive. The longevity of women with ER-positive breast cancer treated with adjuvant endocrine therapy emphasises the need to mitigate the adverse skeletal effects of these therapies in order to maximise benefit. In general, fractures are associated with increased morbidity, mortality and are a high socioeconomic burden. Whilst the efficacy of antiresorptive therapy in preventing bone mineral density loss in postmenopausal women has been established, further clinical trial evidence is required to provide guidance regarding fracture risk reduction, when to initiate and stop treatment, choice of agent and optimal management of bone health in premenopausal women receiving endocrine therapy. In addition, potential oncological benefits of antiresorptive therapies will also need to be considered.

Bone health in women with breast cancer

Women with early, estrogen receptor-positive breast cancer are treated with adjuvant endocrine therapy, using aromatase inhibitors or selective estradiol receptor modulators such as tamoxifen, to deprive breast tissue from the deleterious effects of estradiol action, hence improving long-term prognosis. Aromatase inhibitors and, in premenopausal women, tamoxifen accelerate bone loss and increase fracture risk. Therefore, all women commencing endocrine therapy need a targeted work-up to assess the baseline fracture risk, and monitoring of bone health during endocrine therapy should be individualized based on this baseline risk. While high-level evidence specific to early breast cancer is lacking, non-pharmacologic measures to maintain optimal bone health such as weight-bearing exercise and calcium and vitamin D sufficiency should be implemented in all women. Antiresorptive treatment should be initiated in all women with preexisting fragility fractures (including vertebral morphometric fractures) and should be considered in women with areal bone mineral density (BMD) T-scores < -2.0 (or Z-scores in women aged <50 years) or those experiencing rapid bone loss (≥5% per year), taking into consideration the baseline BMD and other risk factors for fracture. Further clinical trial evidence is required to provide definitive guidance regarding criteria to initiate antiresorptive treatment, choice of agents, and duration of treatment, taking into account potential oncologic benefits of antiresorptive therapy on breast cancer-related outcomes.

Assessment and management of bone health in women with oestrogen receptor-positive breast cancer receiving endocrine therapy: Position statement of the Endocrine Society of Australia, the Australian and New Zealand Bone & Mineral Society, the Australasian Menopause Society and the Clinical Oncology Society of Australia

To formulate clinical consensus recommendations on bone health assessment and management of women with oestrogen receptor-positive early breast cancer receiving endocrine therapy, representatives appointed by relevant Australian Medical Societies used a systematic approach for adaptation of guidelines (ADAPTE) to derive an evidence-informed position statement addressing 5 key questions. Women receiving adjuvant aromatase inhibitors and the subset of premenopausal woman treated with tamoxifen have accelerated bone loss and increased fracture risk. Both bisphosphonates and denosumab prevent bone loss; additionally, denosumab has proven antifracture benefit. Women considering endocrine therapy need fracture risk assessment, including clinical risk factors, biochemistry and bone mineral density (BMD) measurement, with monitoring based on risk factors. Weight-bearing exercise, vitamin D and calcium sufficiency are recommended routinely. Antiresorptive treatment should be considered in women with prevalent or incident clinical or morphometric fractures, a T-score (or Z-scores in women <50 years) of <-2.0 at any site, or if annual bone loss is ≥5%, considering baseline BMD and other fracture risk factors. Duration of antiresorptive treatment can be individualized based on absolute fracture risk. Relative to their skeletal benefits, risks of adverse events with antiresorptive treatments are low. Skeletal health should be considered in the decision-making process regarding choice and duration of endocrine therapy. Before and during endocrine therapy, skeletal health should be assessed regularly, optimized by nonpharmacological intervention and where indicated antiresorptive treatment, in an individualized, multidisciplinary approach. Clinical trials are needed to better delineate long-term fracture risks of adjuvant endocrine therapy and to determine the efficacy of interventions designed to minimize these risks.

Management of Potential Long-Term Toxicities in Breast Cancer Patients

Breast cancer is the most common non-cutaneous malignancy among women, and there are over 3 million breast cancer survivors living in the United States today. Excellent cure rates with modern therapies are associated with substantial toxicities for many women; it is important that health care providers attend to the resulting symptoms and issues to optimize quality of life in this population. In this article, we review management options for potential long term toxicities in breast cancer survivors, with a particular focus on bone health, fertility preservation, premature menopause, cardiac dysfunction, and cognitive impairment.

Fat fraction estimation of morphologically normal lumbar vertebrae using the two-point mDixon turbo spin-echo MRI with flexible echo times and multipeak spectral model of fat: Comparison between cancer and non-cancer patients

PURPOSE

This study aims to compare fat fraction of lumbar vertebrae between cancer and non-cancer patients, using the two-point modified Dixon (mDixon) turbo spin-echo (TSE) MRI with flexible echo times and multipeak fat spectral model.

MATERIALS AND METHODS

Fat fraction was calculated from fat and water images reconstructed by the mDixon TSE technique. Fat fraction of fat-water phantoms measured with the mDixon TSE method was compared with actual fat percentages. Patients who had undergone mDixon spine MRI and dual-energy X-ray absorptiometry within one year and had no bone metastasis were divided into cancer (n=7) and non-cancer (n=23) groups. Fat fraction and bone mineral density (BMD) were compared between the two groups.

RESULTS

Fat fraction of phantoms measured with mDixon MRI was highly correlated with their actual fat percentages (P<0.01, R(2)=0.93). Fat fraction of lumbar vertebrae was significantly lower in cancer patients (58.27±3.16%) than in non-cancer patients (70.48±1.83%) (P<0.01). BMD was not different between cancer (0.912±0.057g/cm(2)) and non-cancer patients (0.876±0.032g/cm(2)) (P=0.58). Fat fraction and BMD showed no significant correlation (P=0.95, R=0.006).

CONCLUSIONS

A two-point mDixon TSE method for assessing fat fraction was reliable. Fat fraction of morphologically normal lumbar vertebrae was significantly lower in cancer patients compared to non-cancer patients, using the two-point mDixon TSE technique.