QUANTIFYING BONE HEALTH IN METASTATIC PROSTATE CANCER PATIENTS DIAGNOSED UNDER 55 WITH OPPORTUNISTIC CANCER SURVEILLANCE SCREENING

Osteoporosis is commonly seen as a disease that rarely impacts young men. As such, young men, even those who suffer hip fractures, are undertreated and underdiagnosed.1 Importantly, prostate cancer treatments, such as androgen deprivation therapy (ADT), have significant detrimental effects on bone.2 However, little is understood with respect to the progression of bone density changes in young patients with metastatic prostate cancer. We aim to quantify the change in vertebral bone density in young patients with metastatic prostate cancer and treatments they receive for bone health. This study follows a retrospective cohort of metastatic prostate cancer patients diagnosed under age 55 treated at our institution. Clinical data from electronic medical records were captured from January 2009 – December 2022 in a REDCap database, include both granular information on disease course, treatment and imaging data.3 For analysis of the imaging data, patients with less than two CT scans were excluded. Imaging-based biomarkers were evaluated using an in-house developed automated pipeline. The pipeline segments the lumbar vertebral bodies4 and erodes the cortical shell to enable analysis of the trabecular bone centrum. Vertebral levels with metastases were identified using both radiology reports and manual review of imaging and were excluded from the assessment of underlying bone health. A threshold value of 135 Hounsfield Units (HU) was used to identify osteoporotic vertebrae.5 We identified 115 patients that met our inclusion criteria. After removal of outliers (1 with Z-score >3), 58 had multiple CT scans for assessing imaging biomarkers over the disease course. Average age at time of diagnosis was 51.27 years (Range: 40–54yrs) and mean survival was 11.73yrs (Range: 1–31). Length of imaging follow-up was 4.26 years on average (Range: 0.46–11.08yrs). A significant decrease in bone density was seen between patients’ first and last CT scan (187.94HU vs 159.62HU; p = 0.0019). Using our threshold for osteoporosis, 7/58 (12.1%) individuals were classified as osteoporotic at first imaging and 18/58 (31.0%) at their final CT scan. Bone density decreased −13.89% on average; median bone density change was −14.25% (Range: −68.06% to 15.51%). Overall change in bone density was −3.27%/year. From the clinical data, 48/115 (41.7%) patients developed a fracture including 11/18 (61.1%) patients that were identified as osteoporotic via imaging biomarkers. Bone health treatments received were Vitamin D alone (15/115, 13.0%), Calcium+Vitamin D (60/115, 52.2%), Bisphosphonates (29/115, 25.2%), and Denosumab (42/115, 36.5%). Despite the young age of these patients at diagnosis, significant reductions in bone density were seen through the course of their disease, reflecting increased risk of bone health related morbidity. Bone health can be tracked over time using opportunistic imaging acquired for cancer surveillance screening. Despite the current guidelines stating that all patients receiving ADT should be receiving Vitamin D and Calcium, 6 only 52.2% were receiving this combined treatment. Cancer surveillance imaging provides an opportunity to track bone health in men with metastatic prostate cancer; decreases in bone density seen even in young men may be used to motivate earlier and more widespread intervention to combat declines in musculoskeletal health.