THU456 Beyond Guidelines: Treatment Of Concurrent Osteogenesis Imperfecta And Metastatic Bone Disease

Disclosure: M. Kanin: None. M. Lechner: None. Introduction: Osteogenesis imperfecta (OI) is a rare inherited skeletal dysplasia characterized by bone fragility and skeletal malformation predisposing patients to multiple, recurrent fractures. Treatment of OI is challenging and requires a multidisciplinary approach with emphasis on physical therapy and exercise in addition to medications. There is limited guidance on treatment in adults given truncated life expectancy. Furthermore, guidance on the treatment of OI in the setting of cancer bone metastases is lacking. We present the unique case of a woman with OI and new fracture in the setting of bone-metastatic endometrial cancer. Clinical Case: A 70 year old woman with Type I OI and endometrial adenocarcinoma initially presented to clinic with left hip and groin pain. Prior OI therapy included at least 10 years of bisphosphonate therapy and 3 years of intranasal calcitonin in her fifties. CT imaging revealed a lytic lesion in the L inferior pubic ramus with an associated pathologic fracture. She was treated with denosumab 120mg s.c. every 3 months for six total doses and palliative radiation to the pubic ramus. She developed osteonecrosis of the jaw and further treatment was terminated. She represented 2 years later with right hip pain and was found to have cancer involvement of her right iliac bone. Labs showed creatinine of 0.48 mg/dL, Calcium 9.8 mg/dl, bone specific alkaline phosphatase 17.9ug/L (7.0-22.4 ug/L), n-telopeptide 18.6 nM BCE (6.2-19.0 nM BCE), and vitamin D-25 48ng/ml. DEXA scan showed T scores at the AP spine of -3.2, LFN of -2.1, and RFN of -2.5. Our patient had a high functional status, minimal pain and acceptable quality of life. Given the presence of active bone metastases, we favored treatment with zolendronic acid 4mg i.v. monthly given her high fracture risk, combined with continued cancer therapy targeted to bone metastases. Clinical Lesson: To our knowledge, there are no guidelines or case reports for optimal treatment of patients with concurrent OI and bone metastases. While bisphosphonates are typically a first line treatment for OI, osteoporosis and metastatic bone disease, the duration and dosing of bisphosphonates varies for each condition. For example, zolendronic acid 4mg i.v. monthly is recommended for cancer patients with metastatic bone disease, while a dose of 5mg i.v. yearly is used for osteoporosis, depending on the severity. Additionally, no clear consensus exists for how often or how long bisphosphonates may be given in adults with OI and treatment durations vary markedly. Other agents that may be considered include denosumab, with indications across bone metastases, osteoporosis, and OI, though this was not available to our patient given her prior complication. Data for newer agents PTH analogs and romosuzumab are lacking. We present this case to highlight the need for an individualized treatment approach in these patients. Presentation: Thursday, June 15, 2023