Physiopathologie, diagnostic et prise en charge des métastases osseuses du cancer de prostate

[Physiopathology and new therapeutic strategies in the management of bone metastases of prostate cancer]

Prostate cancer (PCa) is one of the most common human malignancies that have a strong propensity to spread in the bones. Despite the progress in the diagnosis and the treatment of prostate cancer, bone metastases are present in nearly 95% of men with metastatic PCa at autopsy. Bone metastases are a major cause of skeletal complications which may negatively affect the quality of life and increase morbidity and mortality in men with advanced PCa. Bisphosphonates are potent inhibitors of bone resorption that have demonstrated clinical benefit for the treatment of bone metastases. They are standard of care for the prevention of skeletal complications such as pain and pathological fractures in patients with bone metastases from PCa. More recently, the discovery of the OPG/RANK/RANKL system has permitted to better understand the role of OPG and RANKL as key regulators of osteoclast-mediate bone destruction in both normal bone remodelling and pathologic conditions. RANKL has been shown to contribute to the vicious cycle of bone destruction and tumour growth in PCa. Therefore, the development of new emerging treatment that inhibits RANKL using RANKL antibodies, as denosumab, resulted in a better control and treatment of skeletal complications, with the hope in a near future to prevent bone metastases.

[Bone prevention in prostate cancer]

The bone loss and the fracture risk are enhanced in patients with hormonal deprivation for prostate cancer. The demineralisation can be quantified by BMD (Bone Mineral Density) and prevented by lifestyle and diet therapeutics or new therapeutic agents. These agents may have a preventive effect on metastasis occurrence, but it has to be confirmed. An intra-venous biphosphonate or a sub-cutaneous RANK-inhibitor administration prevent from bone metastasis-related events.

[How to manage bone metastasis in prostate cancer. A case report]

Androgen deprivation therapy with LHRH agonists is the gold standard in the treatment of metastatic prostate cancer. This treatment leads to decrease the bone mass, thus bone mineral density evaluation is recommended after one year of hormonal treatment to measure bone loss. Bisphosphonate is recommended when metastasis occurred during hormonal resistance phase to reduce bone events. The necessity of preventive treatment and the appropriate schedule is not well established. Long term fracture risk should be ideally evaluated with a CT scan and an MRI. Fragmented and focal radiotherapy is considered as the treatment of choice to decrease localized pain. Metastasis surgery has functional results and should be performed before major neurologic symptoms occur. Metabolic radiotherapy is an option for multifocal bone metastases.