**1.4 Complications of bone metastases**

Patients with bone metastases are at risk for bone symptoms and complications such as severe pain, hypercalcemia, bone fractures, pressure, and damage to nerve structures such as the spinal cord [13, 14].

Many bone metastases are asymptomatic and are often discovered accidentally on initial examination or follow-up. In symptomatic cases, pain is the most common symptom. The quality of pain varies from point pain to shooting pain. Involvement or invasion, stretching, or pressure on pain-sensitive structures such as nerves, arteries, and small fractures can lead to pain. Pain due to bone metastases can also be due to mechanical instability in the weakened bone or high intraosseous pressure [15]. Although many factors can cause pain in bone metastases, the major part of the pain is related to bone resorption by osteoclast cells in osteolytic metastases. The pain often intensifies at night and during activity, but direct local invasion and fractures cause persistent pain. Pathological fractures are often seen in osteolytic metastases. Hypercalcemia occurs in 10% of patients and is more common in breast and lung cancers [16].
