Metastasis is the spread of cancerous cells from the site of cancer to another part of the body. Unlike normal cells, these malignant cells tend to move out of the body. Almost all types of cancer can metastasize locally to neighboring tissues and organs. It can also spread to more remote parts of the body through the bloodstream or lymphatic system. The most common sites are the bones, lungs, liver and brain. Symptoms of metastasis and treatment plan may vary depending on the type of cancer. The success of treatment depends on the patient’s age, general health, type of cancer and where it metastasizes. Metastatic cancer is difficult to treat; treatments are mostly aimed at improving the quality of life of the patient.
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What is metastasis?
Metastasis is the spread of cancer to another part of the body. Cancer cells are separated from the original (primary) tumor and spread to other parts of the body in various ways to form a new tumor. This tumor is called a secondary tumor. Secondary tumors are of the same type of cancer as the primary tumor. For example, if breast cancer spreads to the lung, the cancer cells in the lung are not lung cancer cells, but breast cancer cells.
This condition is defined as “metastatic cancer” and is named according to the site where the cancer begins. For example, if lung cancer spreads to bones, it is not bone cancer, but lung cancer metastasis to bone. A metastatic tumor is generally considered to be the 4th (last) stage of cancer.
What is metastatic cancer?
- The ability to metastasize is an important feature that distinguishes malignant tumors from benign (non-cancerous) tumors. Some benign tumors can become larger and may cause significant problems, especially if they are in a confined space such as the brain, but they do not spread to other parts of the body.
- The original cancer can metastasize all over the body. The most common areas are the brain, bones, lungs and liver. Other areas are adrenal glands, lymph nodes, skin and other organs.
- Some cancers are metastatic at the time of diagnosis, while others become metastatic after the cancer has progressed or recurred.
- Sometimes a metastasis can be found without any cancer known. In this case, extensive research is carried out to find the primary source of cancer. If it is not found, it is accepted as a case of metastatic cancer of unknown origin.
What is cancer, how does it occur?
Cancer is a malignant tumor that develops by the uncontrolled division and proliferation of mutated cells in an organ or tissue. There are more than 100 types of cancer. Cancer cells are usually caused by DNA damage.
As cancerous tumors grow, they develop cancer by damaging normal tissues. Although the exact cause is unknown, the main risk factors are all kinds of chemicals including food additives, cigarettes, air-environmental pollution and many drugs.
When a new original (primary) cancer occurs in a person with cancer, it is known as a second primary cancer and is rare. Usually when a person with cancer has cancer again, it means that the first cancer has returned.
Causes of metastasis
Cancer can leave the place where it started and spread to different and remote parts of the body. Normal cells produce adhesion molecules that allow them to adhere to each other. These molecules can be likened to glue. However, cancerous cells lack these adhesion molecules, which makes it easier for them to spread out.
Almost all types of cancer have the ability to metastasize, but whether they will spread to other parts of the body depends on a variety of individual factors.
How does metastasis occur?
- Regional (local): Usually the first stage of cancer metastasis is where the tumor starts. Cancer cells can invade neighboring tissues.
- Through the blood circulation: Cancer cells may break off when the tumor grows and enter the blood vessels near the tumor.
- Through the lymphatic system: The lymphatic system plays an important role in protecting the body from cancer, but it can also function as a channel through which cancer spreads. After locally enlarged, cancers tend to spread to the nearby lymph nodes first through the lymph channels.
- By airways (lung cancer): Recent research shows that lung cancer can also spread through the airways of the lungs.
The spread of cancer cells to new parts of the body occurs in 4 stages:
- Usually leaving the original tumor and entering the bloodstream or lymph system to move them to another part of the body
- Attaching to a blood or lymph wall and move to a new organ
- Growing and developing in new positions
- Preventing attacks that would come from the body’s immune system
Going through all these steps means that the cells that initiate new tumors will no longer be exactly the same as those in the original tumor, which may make treatment difficult.
Symptoms of metastasis
- Bone metastasis: Pain, rarely fracture of a bone with or without minor injuries, numbness of the leg, incontinence, especially severe low back pain
- Brain metastasis: Headache, dizziness, visual and speech problems, nausea, difficulty in walking, or confusion
- Lung metastasis: Cough with or without sputum, blood spitting, chest pain or shortness of breath
- Liver metastasis: Pain, weight loss, nausea, loss of appetite, ascites or jaundice
Metastatic cancer does not always have symptoms. Current symptoms are associated with the original cancer. The nature and frequency of symptoms also depends on the size and location of metastatic tumors.
Diagnosis of metastasis
Metastatic cancer cells have properties similar to those of the original cancer and are not like the cells where the cancer is located. Therefore, it can be diagnosed by medical tests. However, there is no single test to detect metastatic cancer. Different tests can reveal different things.
The tests are determined according to the original cancer type and the symptoms to be investigated. In general, imaging and blood tests such as ultrasound, computed tomography, bone scan, magnetic resonance, pet scan can be carried out, and biopsy can be performed when necessary.
Patients who have completed their cancer treatment are followed up and examined regularly. The first issue investigated during these follow-ups is the possibility of metastasis.
Treatment of metastatic cancer
The metastasis treatment plan is established according to the following criteria:
- Original cancer and where it started
- The extent and location of cancer
- Age and general health of the patient
- Personal treatment options
In some cases, metastasis is treated mainly based on the original site of cancer. For example, if a person’s breast cancer spreads to the liver, it is still treated with drugs used for breast cancer, because the cancer cells themselves have not changed, they just live in a new place.
The main types of treatment for metastasis are:
- Systemic therapy (treatment affecting the entire body): It includes other drugs such as chemotherapy, targeted therapy, hormone therapy and immunotherapy.
- Local treatment (treatment of the cancer area): Includes surgery, radiotherapy and some other treatments.
Doctors may switch to another treatment or try a combination of treatments when their initial treatment no longer works. Organ transplantation is not an option for metastasis.
Once the cancer has spread, it can be difficult to control. Some types of metastatic cancer can be cured by existing treatments, but most cannot be treated. However, there are treatments available for all patients with metastatic cancer. The purpose of these treatments is to slow the growth of cancer or to alleviate symptoms. In some cases, treatments may prolong the life of patient.
Which cancers are most likely to metastasize?
All types of cancer are capable of metastasizing, but some sites of metastasis are more widespread than others. The cancerous cells in the main tumor, usually located in the abdominal cavity, may metastasize more frequently to the liver, lungs or bones. The probability of metastasis according to some types of cancer is as follows:
- Breast cancer: Bones, liver, lungs, chest wall and brain
- Lung cancer: Brain, bones, liver, adrenal glands, other parts of the lung
- Prostate cancer: Bones, lungs, adrenal glands
- Colon and rectal cancers: Liver, lungs and peritoneum
- Stomach cancer: Lymph nodes, lungs, bones, liver, abdominal cavity, brain, ovaries
What is the life expectancy of someone with metastatic cancer?
Life expectancy may vary depending on the type of metastatic cancer, and the age and general health of the patient. Therefore, it is not possible to give a certain time. However, in general, the probability of survival from metastatic cancer is very low; it is responsible for the 90% of cancer deaths. In this case, only treatments that can comfort the patient are applied.
Clinical trials offer treatments that are not yet open to the public. A clinical trial may be the main treatment of metastases or just one of the options. Only 3 to 5% of adults with cancer participate in clinical trials. Clinical trial therapy may or may not be helpful. However, if not, it can provide researchers with information that can help future patients.
Bone metastasis occurs when cancerous cells spread to the bones from their original areas. Nearly all types of cancer can spread to bones, but some types of cancer, especially breast and prostate cancer, are more likely to spread to bones. Bone metastasis can occur in any bone, but occurs mostly in the spine, pelvis and thigh. Bone metastasis may be the first sign of your cancer or may occur years after cancer treatment.
With exceptions, cancer spreading to the bones cannot be cured. Treatments can only help reduce pain and other signs of bone metastasis. Bone metastasis can also cause paralysis and hypercalcemia (high levels of calcium in the blood).
Some cancers can start directly in the bone (bone cancer). These cancers are very different from bone metastases. Bone metastasis is much more common than original bone cancers, especially in adults.
One of the organs in which cancer cells are spread most frequently by the blood circulation is the liver. There are different treatment options depending on the number and size of liver metastases as well as the type and size of the original cancer. In many cases, liver metastasis is treated in the same manner as the original cancer (with the same drugs). Surgical removal of the tumor increases the likelihood of treatment.
The liver is one of the most susceptible organs to radiation, even a small dose of radiation can seriously impair its function and increase the risk of the patient dying of liver failure. Functions of the organ are impaired if metastasis spreads to the whole liver.
The treatment of lung metastases depends on the degree of metastases as well as the original cancer. It is often treated in the same way as the original cancer (with the same drugs). If metastasis causes fluid formation around the lung, fluid may be drawn by needle.
Depending on the number of tumors and the degree of disease in the rest of the body, treatment options may include surgery, radiation therapy, gamma knife therapy, chemotherapy and/or steroids in very specific cases.
Recommendations for metastatic cancer patients
- Doctors may also refer to metastatic cancer as advanced cancer or stage 4, but these terms may have different meanings. For example, a cancer that is large but does not spread to another body part can also be called advanced cancer. Ask your doctor to explain where the cancer has spread.
- Get a second opinion before deciding on a treatment plan. Doctors may have different opinions about the best treatment.
- It is important to ask your doctor about the goals of treatment. These goals may vary during your care depending on whether the cancer responds to treatment. It is also important to know that pain, nausea and other side effects can be managed with the help of your health care team. This is called palliative care and should be part of any treatment plan. Research shows that palliative care can improve your quality of life and make you feel more satisfied with the treatments you receive.
It is important to follow the treatment plan, but coping with emotions and lifestyle challenges is also an important part of living with metastatic cancer. Recommendations for coping with this situation are:
- Talk to another health professional such as a psychologist, psychiatrist, counselor or oncology social worker about your condition.
- Seek options like meditation, yoga, breathing techniques, etc., where you can manage your stress level.
Patients with metastatic cancer may survive for years, depending on the circumstances. Your doctor can help you have the best possible quality of life during this time. Hospitals and health centers have many resources for you and your family.
References: 1- Metastatic Cancer, 2- Lung metastases, 3- Liver metastases