Bone metastases are secondary malignant foci in the bone tissue caused by the spread of cancer cells from the primary tumor of another organ. They are manifested by increasing pain, hypercalcemia and pathological fractures. In some cases, a dense tumor-like formation may be detected in the affected area. With compression of large vessels, circulatory disorders occur, with compression of nerve trunks – neurological symptoms. The diagnosis is established on the basis of anamnesis, complaints, objective examination data, results of laboratory and instrumental studies. Treatment – radiotherapy, chemotherapy, surgical interventions.
Meaning
Bone metastases are a lesion of bone tissue as a result of the spread of malignant cells with blood or lymph flow. They occur in the late stages of cancer. 80% of secondary bone tumors are detected in breast cancer and prostate cancer. In addition, bone metastasis is often found in malignant neoplasms of the thyroid gland, lung cancer, malignant kidney tumors, sarcoma, lymphoma and lymphogranulomatosis. For other neoplasms, the lesion of bone tissue is less characteristic. In ovarian cancer, cervical cancer, soft tissue tumors and gastrointestinal tract, bone metastases are very rarely diagnosed. Treatment is carried out by specialists in the field of oncology, traumatology and orthopedics.
Types
Bone tissue is constantly undergoing processes of resorption and bone formation. Normally, these processes are balanced. Malignant cells in the area of metastasis disrupt this balance by unnecessarily activating osteoclasts (cells that destroy bone tissue) or osteoblasts (young cells of new bone tissue). Taking into account the predominant activation of osteoclasts or osteoblasts, two types of bone metastases are distinguished: osteolytic, in which the destruction of bone tissue prevails, and osteoplastic, in which there is a compaction of the bone area. In practice, pure types of bone metastases are rare, mixed forms predominate.
Most often, secondary foci are detected in bones with a rich blood supply: in the spine, ribs, pelvic bones, skull bones, femoral and humerus bones. In the initial stages, bone metastases may be asymptomatic. Subsequently, they are accompanied by increasing pains. The cause of pain is both mechanical (due to compression) and chemical (as a result of the release of a large number of prostaglandins) stimulation of pain receptors located in the periosteum. Pain syndrome with bone metastases increases at night and after physical exertion. Over time, the pain becomes excruciating, unbearable, the condition of patients is relieved only after taking narcotic analgesics.
Sufficiently large metastases in the bone can cause visible deformation, be detected by palpation in the form of a tumor-like formation or be viewed on radiographs in the form of a destruction site. A serious complication of bone metastases is pathological fractures, in 15-25% of cases occurring in the area of tubular bones, in almost half of cases – in the vertebral region. Sometimes, in the process of growth, bone metastases squeeze nearby large vessels or nerves. In the first case, circulatory disorders occur, in the second – neurological disorders. Severe complications of this pathology also include spinal cord compression and hypercalcemia. Local symptoms of bone metastases are combined with common manifestations of cancer: weakness, loss of appetite, weight loss, nausea, apathy, fatigue, anemia and an increase in body temperature.
Bone metastases symptoms
Hypercalcemia
Hypercalcemia is a life–threatening complication that is detected in 30-40% of patients with bone metastases. The cause of the development is the increased activity of osteoclasts, as a result of which an amount of calcium enters the blood from the destroyed bone, exceeding the excretory abilities of the kidneys. In patients with bone metastases, hypercalcemia and hypercalciuria occur, the process of reverse absorption of water and sodium in the renal tubules is disrupted. Polyuria develops. A vicious circle is formed: due to polyuria, the volume of fluid in the body decreases, which entails a decrease in glomerular filtration. A decrease in glomerular filtration, in turn, causes an increase in the reverse absorption of calcium in the renal tubules.
Hypercalcemia in bone metastases causes disorders of various organs and systems. On the part of the central nervous system, mental disorders, inhibition, affective disorders, proximal myopathy, confusion and loss of consciousness are observed. On the part of the cardiovascular system, a decrease in blood pressure, a decrease in heart rate and arrhythmia are detected. Possible cardiac arrest. From the gastrointestinal tract, nausea, vomiting, constipation and appetite disorders are noted. In severe cases, pancreatitis or intestinal obstruction develops.
On the part of the kidneys, polyuria and nephrocalcinosis are detected. General clinical symptoms include weakness, fatigue, dehydration, weight loss and itching of the skin. Hypercalcemia in bone metastases can remain unrecognized for a long time, since doctors interpret the manifestations of this pathology as signs of progression of the underlying cancer or as a side effect of chemotherapy or radiation therapy.
Pathological fractures
Pathological fractures occur when more than 50% of the cortical layer is destroyed. Most often they are detected in the vertebrae, the second most common is femoral fractures, usually in the neck or diaphysis. A distinctive feature of pathological fractures of the spine with bone metastases is the multiplicity of lesions (at the same time, a violation of the integrity of several vertebrae is detected). As a rule, the thoracic or lumbar region suffers. The damage may be accompanied by compression of the nerve roots or spinal cord.
The cause of a pathological fracture with bone metastases may be a minor traumatic effect, for example, a weak blow or even an awkward turn in bed. Sometimes such fractures look spontaneous, that is, they have arisen without any external causes. The fracture may be accompanied by displacement of fragments. Limb dysfunction in fractures of long tubular bones and neurological disorders in spinal fractures become one of the leading factors in the deterioration of the patient’s quality of life.
Spinal cord compression
Spinal cord compression is detected in 1-5% of patients with metastatic spinal lesions. In 70% of cases, the cause of disorders are metastases to the thoracic vertebrae, in 20% – to the lumbar and sacral vertebrae, in 10% of cases – to the cervical vertebrae. With bone metastases, both acute (with compression by a bone fragment) and gradually progressive (with compression by a growing tumor) disorders can be detected. When squeezed by a growing neoplasm, patients with bone metastases are concerned about increasing pain. Muscle weakness develops, sensitivity disorders are detected. At the final stage, paresis, paralysis and pelvic organ dysfunction occur.
When a bone fragment is compressed, the clinical picture of spinal cord compression develops suddenly. At the initial stages, both types of compression are reversible (fully or partially). In the absence of timely medical care for several hours or days, the paralysis becomes irreversible. Timely adequate treatment can reduce the severity of symptoms, but the restoration of the ability to move independently is noted in only 10% of patients with already developed paralysis.
Diagnostics
The diagnosis is established on the basis of anamnesis (data on the presence of a primary malignant neoplasm), the clinical picture and the results of additional studies. The lack of information about an already diagnosed oncological disease is not a reason to exclude bone metastases, since the primary tumor may be asymptomatic. In the presence of neurological disorders, a neurological examination is performed. At the initial stage of the examination, scintigraphy is performed. Then patients are referred for radiography, CT or MRI of the bone to clarify the nature and prevalence of the lesion. To detect hypercalcemia, a biochemical blood test is prescribed.
Treatment
Treatment tactics are determined taking into account the type and localization of the primary tumor, the number and location of bone metastases, the presence of metastases to other organs and tissues, the presence or absence of complications, the age and general condition of the patient. Surgical interventions are palliative in nature and are indicated in the presence of complications (pathological fractures, spinal cord compression). The purpose of operations for bone metastases is to eliminate or relieve pain, restore limb or spinal cord function and create more favorable conditions for patient care.
When making a decision on surgical intervention, the prognosis is taken into account. Prognostically favorable factors are the slow growth of the primary neoplasm, a long period of absence of relapses, a small single metastasis in the bone, the presence of radiological signs of bone sclerosis after conservative treatment and the satisfactory condition of the patient. In such cases, extensive surgical interventions can be carried out (installation of plates, pins, Ilizarov devices).
With aggressive growth of the primary neoplasm, frequent relapses, multiple metastases, especially with simultaneous damage to internal organs, a large size of bone metastasis, no signs of sclerosis on the X–ray and an unsatisfactory condition of the patient, surgical interventions on tubular bones are not recommended even in the presence of a pathological fracture. In cases where surgical intervention is contraindicated, gentle fixation methods are used (for example, a derotation boot with a hip fracture).
Emergency care for bone metastases complicated by spinal cord compression includes vascular drugs, drugs to improve the metabolism of nervous tissue and high doses of dexamethasone. In case of compression of nervous tissue due to the growth of metastasis in the bone, decompression laminectomy is performed, in case of compression of the spinal cord as a result of a pathological fracture of the vertebra, decompression-stabilizing operations are performed: plate fixation or transpedicular fixation, restoration of vertebrae using bone cement, auto- and allografts, etc.
Chemotherapy and radiation therapy for bone metastases are used in the process of combined conservative therapy, in preparation for surgery and in the postoperative period. In hypercalcemia, rehydration is carried out by intravenous infusion of saline solutions. Patients with bone metastases are prescribed “loop diuretics” (furosemide), corticosteroids and bisphosphonates. The effect of therapy persists for 3-5 weeks, then the course of treatment is repeated.
Forecast
The prognosis for bone metastases is more favorable compared to metastases to internal organs. The average life expectancy is 2 years. The quality, and in some cases, the life expectancy depends on the presence or absence of complications, which determines the importance of preventive measures when detecting metastases in the bones of the skeleton. In case of metastases in the spine, it is recommended to exclude lifting weights and rest several times during the day in a supine position. In some cases, at a certain stage of therapy, wearing a corset or a head holder is indicated. If the femur is affected during the treatment period, it is advised to unload the limb as much as possible using a cane or crutches. Physiotherapy for any bone metastases is contraindicated. Patients need to undergo regular examinations for timely detection of relapses of the disease.