Bone metastatic cancer is a tumor formed when malignant tumors originating from other parts of the body metastasize to the bone through lymphatic or blood circulation routes and continue to grow in the bone. It is generally easier to detect when the primary tumor is clearly diagnosed and metastasized to bone after treatment. However, if the primary tumor site and symptoms are hidden, it is more difficult to diagnose when bone metastasis cancer is the main complaint, or even to diagnose and treat bone metastasis cancer as the primary tumor of bone. Bone metastases are usually found in the crest, pelvis and femur, with breast cancer, lung cancer and prostate cancer as the most common metastases. Generally speaking, breast cancer and lung cancer metastases are mainly osteolytic metastases, while prostate cancer is mainly osteogenic metastases.
Clinical manifestations
1.Site of disease
The common sites of metastasis are the trunk and the proximal end of the limbs, and the distal end of the limbs is the low incidence, while the extremities are rare. In the early stage, most of them are single, but they can also be multiple. Metastatic tumors occurring in the crest are most frequent in the lumbar spine, followed by the thoracic spine, and least in the cervical spine. Breast cancer, lung cancer and kidney cancer tend to metastasize to the thoracic spine; prostate cancer, cervical cancer and rectal cancer tend to metastasize to the lumbar spine; while nasopharyngeal cancer and thyroid cancer tend to metastasize to the cervical spine. In addition, lung cancer, liver cancer and breast cancer also tend to metastasize to the pelvis and upper femur. Most of the primary foci can be found after examination, but there are still some patients who cannot easily find the primary foci.
2.Symptoms and signs
The most common symptoms and signs of metastatic bone cancer include systemic wasting symptoms, local pain of metastases, pressure symptoms, pathological fracture, etc. Most patients come to the clinic with local pain and pathological fracture. About 40% of patients have a history and signs of primary malignancy, and metastatic symptoms appear during or several months or years after treatment. Most patients have no history and signs of primary tumor, and the first symptom is the symptom of metastasis, which causes diagnostic difficulties, such as liver cancer, thyroid cancer, kidney cancer, etc. There are often no primary symptoms.
(1) Pain, the most common symptom, is lighter in early stage and changes from intermittent to persistent, which is easy to attract attention in severe cases and easy to be ignored in light cases. Those located in the crest may manifest as pain in the lumbar region, thoracic back, and neck. Those in the thoracic spine are often accompanied by unilateral or bilateral intercostal neuralgia. Those in the lumbar spine may present with abdominal pain. The pain is characterized by ineffective braking. The pain is increasing in severity. Those located in the pelvis are often associated with hip and medial femoral pain; those located in the upper femur and upper humerus are often associated with joint dysfunction.
(2) Masses. Some patients visit the clinic because of masses. Bone metastases located deep in the bone are not easily detected in early stage. In the vicinity of important nerves, the enlarged tumor may have more or less compression symptoms, producing numbness, muscle weakness or atrophy. In many cases, the lesions of bone metastatic cancer are found only when pathological fracture occurs.
(3) Compression symptoms. Crestal metastatic cancer may show compression symptoms of crestal medulla, cauda equina or nerve roots, resulting in radicular neuralgia, hypesthesia, muscle weakness or even paralysis, and sphincter dysfunction. Patients may be admitted to hospital due to paralysis. Pelvic metastatic cancer may cause compression symptoms of rectum and bladder, and urinary and fecal dysfunction. Limb bone metastasis cancer may cause compression symptoms of blood vessels and nerve trunk.
(4) Pathological fracture, which is often the first symptom, occurs with minor trauma or without any causative factors. Once pathological fracture occurs, the pain is aggravated and swelling is obvious. In the crest, paralysis occurs quickly.
(5) Systemic symptoms, those with primary cancer symptoms have poor general condition, including anemia, emaciation, low fever, weakness, loss of appetite, etc. For those without primary cancer, the general condition is better, and some patients may develop general symptoms soon.
Auxiliary examination
Auxiliary examinations are often used as clinical indicators to determine the progress, treatment effect and prognosis of bone metastatic cancer.
Routine examination may show lower hemoglobin, lower blood red blood cell count, higher blood white blood cell count, faster sedimentation, lower blood albumin, inverted A/G ratio, etc. Alkaline phosphatase (ALP), acid phosphatase (ACP), lactate dehydrogenase (LDH), blood calcium, blood phosphorus, etc. should also be examined.
Bone marrow examination. Tumor cells can be found in bone marrow smear in case of bone metastasis.
3.Pathological examination, biopsy should be performed when bone metastasis is suspected, the purpose is to clarify the diagnosis and choose the treatment method.
4.Tumor marker detection, which is helpful for diagnosing primary cancer and the progress of tumor metastasis.
5.X-ray examination, which shows destructive changes of bones, lesions are mostly confined in bones with unclear edges, sometimes it is not easy to distinguish from primary bone tumor.
6. ECT (nuclear scan) is one of the common examinations for bone metastases, which can detect the early metastatic cancer.
7.PET-CT (Positron Emission Tomography) examination can observe tiny lesions that are difficult to be detected by general imaging means.
8.CT examination can determine whether there is a tumor and accurately locate it, and the nature of the tumor should be combined with clinical judgment.
9.MRI examination is more sensitive to diagnose bone metastases.
10.B ultrasound examination, B ultrasound is more suitable for bone metastases with osteolytic bone destruction as the main cause.
11.Angiography can show typical malignant changes, such as rich blood flow, capillary hyperplasia but disorganized, and “vascular lake” phenomenon. Interventional treatment can also be performed at the same time of angiography.
Diagnosis and Differential Diagnosis
After the diagnosis of primary tumor, the diagnosis of bone metastasis is relatively easy. Bone metastatic cancer with bone tumor as the first symptom often relies on auxiliary examination in diagnosis. For patients with malignant tumor, monitoring of tumor micrometastasis should be carried out; X-ray examination should be performed on suspicious sites, and nuclear, CT and MRI examinations should be performed as appropriate; biopsy is feasible when necessary, and biopsy is a reliable means to diagnose tumor and the main means of differential diagnosis; for patients without history of malignant tumor, comprehensive and careful examination should be performed to find the primary lesion. Attention should be paid to the diagnosis of primary osteosarcoma, lymphoma, myeloma, etc.
The treatment of bone metastases is still aimed at reducing pain, preserving function, improving the quality of survival and prolonging life. Depending on the specific situation, radiotherapy, chemotherapy, interventional therapy, biological therapy, Chinese medicine and, if necessary, surgery can be used. The treatment of primary tumor is the main part of the whole treatment. The treatment plan should be formulated according to the patient’s condition, the severity of the symptoms of bone metastases, the purpose and possible consequences of each treatment, and the wishes of the patient and family.