SUN-786 - DXA with Excess Bone Mass in A Patient with Osteoporosis and Breast Cancer

We present a case of an 80-y-old female patient with known history of osteoporosis following a fragility fracture of the left hip and wrist in 2021 despite normal BMD by DXA at baseline. She was also found to have radiographic T4 and T9 vertebral fractures (2021). She was diagnosed with breast cancer (2017) (invasive ductal carcinoma ER, PR positive, HER2 negative), status post lumpectomy, radiotherapy, and Anastrozole. In 2020, recurrent (vs second primary) invasive ductal carcinoma of left breast (ER positive, PR, HER2 negative) was treated with partial mastectomy, adjuvant chemotherapy, and radiotherapy. Since cancer recurred on Anastrozole, she was switched over to Exemestane (April 2021), which she remained on. She received Zoledronate 4 mg every 6 months for 6 doses ending in May 2025. She was previously treated with Alendronate for 4 years, ending in January 2019.
Upon her yearly visit for bone health, the patient was asymptomatic and in her usual state of health. A DXA study on a Hologic Horizon A machine showed L1-L3 T-score +2.5, Z-score +5.1. L4 was excluded due to previous spinal surgery with metal hardware at L4-L5 level. Right TH showed T-score –0.8, femoral neck T-score –0.1. When compared to a previous study 13 months earlier, there is an increased BMD of the lumbar spine of 0.170 gm/cm2 (+15.2%, LSC 0.024 gm/cm2). There was no significant change of BMD at TH. Upon further review of the detailed lumbar spine results, almost all of the BMD gain was at L2 vertebral body (1.172 gm/cm2 => 1.631 gm/cm2) with T-score for L2 increasing from +1.3 to +5.5 (Z-score increasing from +3.9 to +8.1). The gain was in the bone mineral content (BMC) (18.76 gm =>25.96 gm) with stable area (16.00 cm2 =>15.92 cm2), which is atypical for vertebral fractures. The corresponding scan image of the lumbar spine showed sclerosis of L2 vertebral body not previously seen in the older scan image from September 2024.
Plain X-rays of the lumbar spine revealed a sclerotic L2 vertebral body. This prompted further imaging with CT scans of chest, abdomen and pelvis, and nuclear bone scans, which showed sclerotic lesions in T3, T8, T9, T10, L1, L2, L4, L5, as well as a 9 mm lingular lung nodule. A bone biopsy of L2 confirmed the presence of metastatic carcinoma consistent with breast origin.
In summary, an 80-y-old female patient with osteoporosis and breast cancer was found to have metastatic bone disease first detected as a BMD increase in a single vertebral body during monitoring within 13 months between DXA studies. We stress the value of monitoring BMD in patients with breast cancer as part of a multidisciplinary bone health maintenance plan. It is important not to ignore unexpected BMD gains out of proportion to response to administered pharmacologic therapy. DXA scan images provide a wealth of information that can explain BMD trends, and study details pertaining to specific vertebral bodies can detect new and unsuspected pathologies.

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