Postmenopausal Patient With ER+ Early-Stage Breast Cancer: Bone Protection and Shared Decision-Making

Diagnosis and Treatment

A 69-year-old woman presents with an abnormal mammogram to a breast surgeon at her local hospital. She undergoes a left breast biopsy, which shows infiltrating ductal carcinoma. Further testing reveals T2N0M0 ER/PR-positive HER2-negative, Oncotype DX low (9) disease. She undergoes lumpectomy followed by radiotherapy and begins a planned 5-year course of anastrozole.

Bone Protection Therapy and Shared Decision-Making

Per NCCN Guidelines regarding patients with breast cancer who take an aromatase inhibitor,¹ her oncologist orders a baseline bone density scan, and results show a T-score of -1.4 in the lumbar spine, and -1.6 in the right hip. He also checks her vitamin D level, which is low at 27 ng/mL. The oncologist discusses the importance of maintaining bone health with the patient. Even though she has not yet developed osteoporosis (defined as a T-score of < -2.5),² she is at risk for further bone loss due to age and her prescribed aromatase inhibitor.

After a shared decision-making discussion, the oncologist and patient agree that she will start on a bone-modifying agent (BMA) to reduce her risk of further bone loss. She chooses to start denosumab at a dose of 60 mg every 6 months as a subcutaneous injection, as she does not want infusion therapy and this treatment aligns with her office visits for follow-up.

She begins the denosumab treatment after both a routine dental care evaluation to ensure she is not at increased risk for osteonecrosis of the jaw (ONJ) and a patient education meeting with her oncology clinical pharmacist to review side effects and a monitoring plan. She also begins a daily calcium/vitamin D supplement.

Follow-up

After starting the BMA, the patient has checkups every 6 months to monitor her vitamin D and calcium levels and to evaluate for complications such as ONJ. During these office visits, she also receives her denosumab injections and has a follow-up visit with her care team, alternating between her medical oncologist and nurse practitioner.

She also undergoes a bone density scan every 2 years to evaluate change and response to the bone agent. Her first bone density scan 2 years after starting treatment shows an improved T-score of -1.3 in both the lumbar spine and hip. Now that she is no longer at high risk for osteoporosis, she stops taking the denosumab and begins taking an oral bisphosphonate to prevent osteoporosis.

Discussion

A bone density scan score of -1.0 to -2.5 indicates that a patient has osteopenia and may be at risk for developing osteoporosis.² This patient had a score of -1.4 and is postmenopausal, so per NCCN guidelines for ER-positive early-stage breast cancer, she was placed on anastrozole for 5 years for treatment of her breast cancer.¹ Denosumab at a dose indicated for osteoporosis was started given her high risk for progression from osteopenia to osteoporosis while on an aromatase inhibitor. This is different than the dosing for prevention of skeletal-related events in metastatic breast cancer (120 mg every 4 weeks).^3,4 Clinical judgment and patient engagement shared decision-making were pivotal to this plan. Careful prescription, monitoring, and management of BMAs in practice for individuals with breast cancer is a collaborative effort in which oncology APPs, including pharmacists, nurse practitioners, and physician assistants, all play a crucial role.

References

1. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology. Breast Cancer Version 2.2023. Published February 7, 2023. https://www.nccn.org/professionals/physician_gls/pdf/breast.pdf
2. Shapiro CL. Management of osteoporosis in women with breast cancer. Breast Cancer Manag. 2020;9. https://doi.org/10.2217/bmt-2020-0012
3. Xgeva (denosumab) prescribing information. 2010. https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/125320s094lbl.pdf
4. Prolia (denosumab) prescribing information. 2010. https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/125320s5s6lbl.pdf