What are?
Bone metastases are a frequent complication of advanced malignancies. After the lung and liver, bone is one of the most common sites of metastasis for most cancers.
Causes
Metastases occur when cancer cells, through the blood or lymphatic flow, migrate from the site of the primary tumor to other organs or tissues, taking root and giving rise to new neoplastic formations. In some cases, these cells reach the bones, where they begin to proliferate.
Bone metastasis can be the first sign of cancer or it can occur years after treatment of the primary cancer.
Note. Bone metastases are more common than primary bone tumors, especially in adults.
Osteolytic and Osteoblastic Metastases
Under normal conditions, bone undergoes continuous remodeling: osteoclasts mediate resorption (break down bone tissue), while osteoblasts are responsible for bone deposition (build bone tissue). The dysregulation of these processes by cancer cells leads to two different phenotypes:
- Osteolytic bone metastases: characterized by the destruction of normal bone in a particular area; it is the most common damage in cancers that have spread from the lung, thyroid, kidney and colon.
- Osteoblastic bone metastases: The deposition of new tissue occurs in response to the spread of cancer. The process results in abnormal growth, where the bone structure is weak and deformed. It is most often found in cancers of the prostate, bladder and stomach.
This distinction is not absolute; many patients with bone metastases have both osteolytic and osteoblastic lesions.
In both types of injuries, dysregulation of the normal bone remodeling process leads to bone malformation. The bones thus altered are unable to withstand normal mechanical stress and are exposed to pathological fractures, compression and instability.
Symptoms
Bone metastases can cause a wide range of symptoms, which can impair quality of life or shorten patient survival. Some cancers more easily metastasize to the bones: breast, lung, prostate, thyroid, and kidney.
Signs and symptoms of bone metastases include:
- Bone pain (most common symptom);
- Fractures. Bones weakened by the neoplastic process break more easily. A fracture after a minor injury is a possible sign of bone metastasis.
- Anemia. Decreased red blood cell production is a common "blood abnormality in patients with bone metastases."
In addition to these local effects, osteolytic metastases can cause hypercalcemia (increased blood calcium levels). Other effects of bone metastases may include: spinal cord compression, decreased mobility, urinary and fecal incontinence. Patients with localized spinal bone metastases may develop nerve damage, which can lead to paralysis and loss of use of the legs and / or arms.
Diagnosis
In some cases, bone metastasis is discovered before or at the same time as the primary tumor. Doctors can determine the site of origin of the disease by characterizing the type of cancer cells that make up the metastases. Importantly, many cancer patients present with bone and joint pain as a side effect of some chemotherapy regimens.
Medical history and physical examination
The first approach is aimed at understanding the patient's general health status. If doctors suspect that bone metastasis is responsible for symptoms, they collect information about previous medical conditions and their management. After the anamnesis, a physical examination is performed, mainly focused on the painful areas.
Diagnostic for images
After the history and physical examination, doctors take a series of X-ray images of the suspicious region. The examination allows to determine if a primary tumor has given rise to metastases and the possible degree of bone involvement. Other imaging techniques help determine the severity of the lesions: bone scan is useful for determining whether other bones, in addition to those in which the symptoms are concentrated, are affected by the metastasis; in some cases, positron emission tomography (PET), computed tomography (CT), and / or magnetic resonance imaging (MRI) may be indicated, especially in cases where the spine or pelvis may be involved.
Blood and urine analysis
Cancer patients should be regularly evaluated with a complete blood count, as deficiency of red blood cells (anemia) is often found in metastatic bone disease. In addition, the alteration of some blood chemistry parameters (electrolytes, calcium and alkaline phosphatase) may be indicative. In particular, in patients with metastases, blood tests allow to detect protein markers of bone loss and higher levels of calcium in the blood. Urinalysis can show blood in patients with renal cell carcinoma, while thyroid function tests and evaluation of tumor markers - such as CEA (carcino-embryonic antigen), CA-125 (Cancer Antigen 125) and PSA (prostate specific antigen) - can be altered in patients with specific tumors.
Bone biopsy
The physician must determine whether the metastasis derives from a primary bone tumor (sarcoma) or from a neoplasm that began in another "site. A bone biopsy involves taking a sample of tissue, to be analyzed to characterize the tumor cells and define this aspect.
Treatment
To determine the best treatment plan, doctors need to consider a number of factors. Often, the choice between treatment options depends on where the bone metastases have developed and their extent.
Unfortunately, in many cases, the cancer has already progressed to the point where multiple sites are involved by the time of diagnosis. As a result, treatment is often focused on symptom management and is not intended to be curative.
Depending on these factors, the treatment of bone metastases often involves a comprehensive approach that may include one or more of the following approaches:
- Treat the primary tumor;
- Reduce the extent of metastases;
- Manage pain and damage to the bone structure.
Common treatment options for bone metastases include surgery to stabilize weak or broken bone, radiation therapy, and some medications to control pain and prevent further spread of the disease.
Medicines
Drug treatment options for patients with bone metastases include:
- Anti-resorptive drugs: These are commonly used to treat people with osteoporosis, but they can also help patients with bone metastases. These drugs can strengthen bones, reducing pathological fractures and pain. Anti-resorptive drugs can also decrease the risk of developing bone metastases elsewhere. Therapy can cause temporary pain and kidney problems. In rare cases, anti-resorptive drugs increase the risk of avascular osteonecrosis.
- Medicines to control pain: Pain relievers, such as ibuprofen or morphine, can control symptoms caused by bone metastases.
- Chemotherapy: involves the use of drugs to stop the proliferation of cancer cells. The effect of chemotherapy is systemic, therefore it affects the whole organism and also damages healthy cells. For this reason, the therapeutic regimen is carried out in cycles that include periods Rest Chemotherapy drugs are administered orally, intravenously or intramuscularly Side effects depend on the duration of treatment and the dose used, may include fatigue, hair loss, nausea and vomiting.
- Hormone therapy: Some types of cancer are sensitive to hormones, such as estrogen, which can stimulate the proliferation of cancer cells. Hormone therapy therefore has the objective of limiting the effects of hormones on disease progression. Treatment may involve taking drugs that suppress the production of the hormones responsible or block their interaction with cancer cells. The therapy has menopause-like side effects (in women) related to hormonal fluctuations, including hot flashes, anemia and loss of sexual desire.
- Bisphosphonates: These drugs can be used to stabilize bone mass and slow down the degenerative process of metastases. Bisphosphonates are also useful for the treatment of pain and hypercalcemia. The oral form is generally well tolerated, but long-term therapy can have several side effects, such as: arthralgia and osteonecrosis of the jaw.
Radiotherapy
Radiation therapy involves the destruction of cancer cells by administering high-energy radiation, directed to the metastatic tumor and adjacent tissue. Treatment allows you to control the progression of the disease and prevent pathological fractures. Depending on how many areas are affected by the metastasis, one or more bones may be targeted for radiotherapy.
Treatment may be an option if the condition causes pain that cannot be effectively controlled with pain medication. Depending on the situation, the radiotherapy regimen may involve administering one or more doses, for a specified period of time. side effects depend on the site being treated. In general, radiation therapy causes fatigue, mild skin reactions, stomach upset and diarrhea. The primary goal of treatment is to relieve pain while producing minimal side effects. Although different cancers respond variably to radiation, in general, radiation therapy is unlikely to be curative; therefore, the physician must balance the potential benefits and risks of treatment for each patient. In case of multiple bone metastases, radiopharmaceuticals can be administered intravenously. Once in the body, the radioactive particles travel to areas of bone metastasis and selectively produce their effect.
Surgical treatment
The goals of surgical treatment for bone metastases are "to relieve pain and restore skeletal strength. Surgical procedures can help stabilize a bone at risk of breaking or repair a fracture."
- Surgery to stabilize the bone. If the bone is weakened and at risk of fracture due to bone metastasis, surgeons can stabilize it using orthopedic fasteners, such as metal plates, pins and nails. The procedure can relieve pain and improve function and mobility of the treated region. In some cases, bone cement is inserted into the defect created by the tumor. This gives strength to structures that cannot be easily stabilized with fasteners, such as the pelvic bones and spine. This procedure can also reduce pain due to bone metastases.
- Surgery to repair a broken bone. If bone metastases have resulted in a fracture, surgeons can repair the injured bone. This surgery involves the use of metal plates, nails, and screws to stabilize the bone. Another option is to replace the bone segments with prosthetics.
Conclusions
Response to treatment depends on:
- Location and extent of metastases;
- Pain intensity;
- Number of painful sites;
- Location of the primary tumor;
- Type of lesions (osteolytic vs. osteoblastic);
Bone metastases are usually not curable. However, advances in surgical techniques, as well as the use of medical radiation and appropriate drug therapies, have significantly improved the quality of life of the cancer patient with bone metastases.
Early identification and therapy of a metastatic tumor correlates with a more favorable clinical outcome.
