KP-A038

To describe the use of anti-osteoclastic medications (i.e., bisphosphonates and receptor activator of nuclear factor kappa beta (RANK) ligand inhibitors) in treating choroidal osteoma.

A 42-year-old male with bilateral posterior choroidal osteomas showed extensive outer retinal atrophy in the right eye secondary to decalcification of a choroidal osteoma and progressive extension of retinal pigment epithelial atrophy in the left eye encroaching on the macula with subtle changes in the choroidal osteoma. Bisphosphonates (i.e., oral alendronate 70 mg weekly) or RANK ligand inhibitors (i.e., subcutaneous denosumab 60 mg every six months) were initiated to prevent calcium resorption.

After the introduction of more directed therapy, there was stabilization of the patient's condition over the next nine years while under bisphosphonate treatment, followed by a switch to RANK ligand inhibitor therapy and later bisphosphonate treatment again. This was made evident through stability in fundus photography, enhanced depth imaging optical coherence tomography, and B-scan ultrasonography regarding outer retinal layers thickness, and choroidal osteoma thickness and calcification.

Anti-osteoclastic therapy using bisphosphonates or RANK ligand inhibitors could be a new treatment paradigm to prevent resorption of choroidal osteomas and prevent the subsequent atrophy of outer retinal layers.

A patient with bilateral posterior choroidal osteomas was treated with bisphosphonates and RANK ligand inhibitors to prevent osteoma resorption in the better-seeing left eye. This has led to stability over six years of outer retinal layers thickness, choroidal osteoma thickness, and choroidal osteoma calcification.

Breast cancer is the second most common cancer worldwide. There are four main subtypes of breast cancer, one of which involves positivity for human epidermal growth factor receptor 2 (HER2). Here, we present a case series of unusually long survival in three patients with HER2-positive metastatic breast cancer. All cases involved post-menopausal women with bone-only metastases undergoing treatment with the HER2-targeted therapy trastuzumab and the receptor activator of nuclear factor kappa-Β ligand (RANK-L) inhibitor denosumab. Our three patients survived for 17, 13, and 11 years, respectively, from the time of metastasis. The patients who survived for 17 and 13 years both presented with metastatic disease at diagnosis, while the patient who survived for 11 years with metastatic disease was known to have non-metastatic breast cancer for four years prior. We also report the development of foot fractures from minor trauma, as low as walking, despite a bone density reported as normal in the patient with 17 years of treatment. These unusually long survival times and the unusual location of the fractures are questioned to be secondary to the long duration of treatment with HER2-targeted therapy and RANK-L inhibitor therapy. Our case series is the first to describe the use of trastuzumab and denosumab in HER2-positive metastatic breast cancer. All three reported cases had no clinical or radiographic disease progression at the time of reporting. Furthermore, our case of survival for 17 years represents the longest survival time reported yet, raising the possibility of a synergistic relationship between RANK-L inhibitors and HER2-targeted therapy in the long-term control of HER2-positive metastatic breast cancer. This manuscript discusses evidence from primary studies on HER2 and receptor activator of nuclear factor kappa-Β (RANK) signalling and drug responses and hypothesizes on possible mechanisms of synergism. Given that treatment of HER2-positive breast cancer has historically not involved RANK-L inhibition, this study may outline future areas of research in improving treatment algorithms, especially for bone-only metastatic disease.