Tumoral Bone Strength Assessment by Numerical Simulation Using Quantitative CT : the MEKANOS Study

Osteolytic bone metastases and myeloma bone lesions are responsible of long bone and vertebral fractures leading to restricted mobility, surgery and medullar compression that severely alter quality of life and that have a huge medico-economic impact. It has been estimated that 50% of the patients with bone metastasis will encounter bone complications. In the recent years, Bone Oncology Multidisciplinary Meetings have been developed to optimize bone metastases management for each patient in harmony with oncology program. The assessment of the fracture risk of bone metastasis remains fairly empirical and is based on simple radiography. The Mirel's score for long bones is focused on the extent of cortical defect caused by bone metastasis to identify high-risk patients at risk of fracture during surgery. It is old, little used in routine and lacks sensitivity and specificity. The SINS (Spinal Instability Neoplastic Score) score is the reference for vertebrae. Today, most patients with fracture-risk bone metastasis benefit from a lesion-centered CT scan to better characterize its extent and position but the interpretation remains qualitative. Metastases are considered as an air cavity and the mechanical properties of the tumor are not evaluated. However, many other parameters from the CTscan are available such as cortical or trabecular compartment densitometry, cortical thickness, tumor volume, and position of lysis in the bone. Based on experience acquired by the service in the evaluation of bone mechanical strength on benign bones, the investigator aim at integrating in the numerical simulation the mechanical properties of both bone and tumor, in order to evaluate the mechanical strength of the pathological bone using a numerical simulation model (finite element analysis-FEA). MEKANOS will enroll patients with bone metastases of breast, lung, kidney, thyroid or bladder cancer and myeloma lesions affecting the vertebrae or the upper end of the femur. The resistance obtained will be compared to that of an intact bone. The best predictive parameters of mechanical strength (position of lysis, tumor nature, and bone architecture) will be then determined. Finally, the added value of this technique in relation to historical fragility scores (Mirel's and SINS scores) will be assessed. The ultimate goal is to provide tools to assess fracture risk and improve the preventive management of bone metastases in harmony with the referring oncologist