Bone Metastases
Summary of Key Points
Causes
• Tumor cells are attracted to particular niches in bone and may remain dormant for prolonged periods, as controlled by microenvironmental cues.
• Osteolytic damage is mediated largely by stimulation of osteoclasts via tumor-derived cytokines; intermediary cells, including immune cells and osteoblasts, are involved.
Diagnosis
• Differential diagnosis includes osteoporosis, degenerative disease, and Paget disease.
• The isotope bone scan is a sensitive test to detect the presence of skeletal pathology but gives little information about its nature.
• Structural information on skeletal damage from metastatic bone disease is best obtained by skeletal radiography supplemented with computerized tomography and magnetic resonance imaging.
• Positron emission tomography provides functional information that may aid in diagnosis.
Evaluation of the Patient
• An assessment of the patient’s symptoms and activity status is essential.
• Skeletal radiography assesses response to treatment, but the information is delayed and the method is insensitive.
• Early indications of response of bone metastases to treatment can be obtained by monitoring biochemical markers of bone metabolism.
• Isotopic bone scanning is not useful in monitoring response to treatment.
Treatment
• Antitumor treatments such as external beam radiotherapy, endocrine therapy, cytotoxic chemotherapy, targeted biological agents, and radioisotope therapy have a role in the multidisciplinary palliative treatment of metastatic bone disease.
• The bisphosphonates and the receptor activator of nuclear factor κ ligand inhibitor denosumab are inhibitors of osteoclast activity and have become important agents for the treatment of metastatic bone disease because they relieve symptoms, allow bone healing, and delay complications.
Complications
• Complications include pain, impaired mobility, pathological fracture, spinal cord compression, cranial nerve palsies, nerve root lesions, hypercalcemia, and suppression of bone marrow function.
