All about metastatic cancer, how it spreads, diagnosis and treatment
Cancer, when detected at an early stage, has a higher chance of successful treatment than when it is diagnosed at a later or advanced stage. However, most cancers go undetected until they spread to other body areas, causing more harm.
Written By
Oluoma Vivian AnekeHuman Anatomist
Reviewed By
Grace EnehMedical Doctor (MBBS) | Consultant Neurologist
Cancers that have spread to other parts of the body are known as metastatic cancers.
Metastatic cancer always poses a challenge in treatment and is the leading cause of cancer death. In 2020, metastatic cancer accounted for about 1 in 6 deaths (nearly 10 million deaths), according to the World Health Organisation.
In a previous article, SemicHealth discussed the meaning of cancer and whether humans are born with cancer cells. In this article, we will discuss metastatic cancer, how it spreads, common sites of cancer metastasis, survival rate, diagnosis, and treatment.
Meaning of metastatic cancer
Metastatic cancer is a malignant tumor that has spread. Cancer metastasis occurs when cancer cells break out from their original location/primary tumor and travel to other parts of the body.
Therefore, cancer is said to have metastasized when it has gone beyond its original location and has traveled to other body parts of the body through the bloodstream or lymphatic system.
The ability to metastasize is what makes cancerous tumors even more life-threatening, and it is one of the major differences between benign tumors and malignant tumors. While benign tumors are harmless and don't spread, malignant tumors are harmful and spread.
Metastatic cancer has higher death risks because it often involves cancerous tumors spreading to delicate and vital organs like the brain, lungs, and liver.
About half of patients diagnosed with cancer already have clinically detectable metastatic disease at the time of diagnosis.
Difference between advanced and metastatic cancer
The terms "advanced cancer" and "metastatic cancer" are often used interchangeably, but they don't exactly mean the same thing.
Advanced cancer is simply cancer that has gotten to its final stage, such as stage IV prostate cancer. Most times, they cannot be cured. On the other hand, metastatic cancer is cancer that has spread from its original site to other body parts.
Most advanced cancer has metastasized (spread to other parts of the body), but there are exceptions.
In some cases, cancer gets to its advanced stage but doesn't spread to other parts of the body.
For instance, some brain cancers that grow large in size and obstruct blood flow to essential brain structures may be considered advanced even though they haven't spread. They are considered advanced cancers because they are large, life-threatening, and difficult to treat.
Likewise, even though most advanced cancers spread to other body parts, not all metastatic cancers are advanced cancers. For instance, cancers like testicular cancer can metastasize but still be curable.
Advanced cancer is also referred to as terminal cancer. Healthcare providers often provide palliative care for people with cancers in this stage to keep them comfortable till they pass on.
Providing palliative care may involve shrinking the cancerous tumor, slowing the cancer growth to help the patients live longer, and giving medications to help relieve their symptoms.
How cancer spreads
Through the blood vessels, cancer cells get to the other parts of the body where it metastasize
Cancer cells have the potential to break off from their primary tumor. Most times, they move into nearby blood and lymph vessels. Through these vessels, they get to other parts of the boy.
Some metastatic cancer cells die off on their way to other body parts. However, some of them get to survive and stick to the wall of blood and lymph vessels. From the vessel wall, they move to other body tissue. The blood vessels serve as their route of spreading.
When they migrate to other body tissue, they start to divide and form metastatic tumors. For cancer cells to spread, they will have to:
- Break away from the original tumor and enter the bloodstream or lymph system
- Attach to the wall of a blood or lymph vessel
- Move to a new body part
- Grow and thrive in the new part
- Escape attacks from the immune system
Common sites of cancer metastasis
The sites where cancer cells spread also depend on the site where the tumor first formed. However, the most common site for cancer metastasis is the bone, liver, and lung.
Breast cancer spreads typically to the bones, lungs, liver, and brain. Colon cancer often spreads to the lungs and liver and is the third most common cancer diagnosis and the second deadliest for both genders.
However, it is essential to note that metastasized cancer retains the same name as the primary cancer. This means that if colon cancer spreads to the liver, it remains colon cancer and not liver cancer.
The metastasized colon cancer will be referred to as "metastatic colon cancer" because it migrated from its original site of formation in the colon. The same applies to other types of metastatic cancer.
The table below shows the different types of cancer and the common sites of metastasis.
Type of Cancer | Common sites of Metastasis |
|---|---|
Breast | Bone, liver, lung |
Kidney | Adrenal Gland, bone, brain, liver, lung |
Bladder | Bone, liver, lung |
Colorectal | Liver, lung, peritoneum |
Ovary | Liver, lung, peritoneum |
Lung | Adrenal gland, bone, brain, liver, lung |
Melanoma | Bone, brain, liver, lung, skin, muscle |
Pancreas | Liver, lung, peritoneum |
Prostrate | Adrenal gland, bone, liver, lung |
Stomach | Liver, lung, peritoneum |
Uterus | Bone, liver, lung, peritoneum, vagina |
Thyroid | Bone, liver, lung |
Survival rate for metastatic cancer
The survival rate for metastatic cancer depends on different factors such as the type of cancer and site of metastases, your doctor will explain this to you
Most times, when patients are diagnosed with a terminal illness, the first question usually is, “how much time do I have?”
In a bid to answer this question, physicians often predict how much time they have to live, depending on the type and stage of the cancer. In most cases, the predictions are accurate.
So, what factors determine the life expectancy of metastatic cancer? On what basis are assertions made?
The survival rate of metastatic cancer varies with individuals and largely depends on the type of cancer. Doctors usually focus on treatment and survival rather than trying to predict how long the person has to live.
Some of the factors considered when looking at the survival rate include:
- The degree to which a patient can carry out personal activities like bathing, using the toilet, and dressing.
- The severity of the symptoms
- The site of metastases
- If the person is having difficulty in swallowing, shortness of breath, dry mouth, weight loss, lack of appetite
- Progressive loss of strength
Symptoms of metastatic cancer
There are no definite symptoms for metastatic cancers. The symptoms vary based on the type of cancer and the site of metastasis. However, just like primary cancers, metastatic cancers can cause symptoms like:
- Extreme fatigue
- Unexplained weight loss
- Pain in different areas of the body
- Respiratory problems like difficulty in breathing
Sometimes the symptoms can be specific to the site of metastasis. For example:
- Cancer cells that metastasize to the brain and may cause headaches, seizures, or dizziness
- Cancer cells that metastasize to the bones may cause pain and increase fracture risk
- Cancer that metastasizes to the lung may cause respiratory problems like difficulty breathing or shortness of breath
- Cancer that metastasized to the liver may cause jaundice or abnormal swelling of the liver
Diagnosis of Metastatic Cancer
There are different methods of diagnosing metastasis. Your doctor will diagnose you depending on the type of cancer, the location, and the symptoms.
The most common diagnosis is usually through blood tests, although sometimes the blood tests are barely sufficient.
A significant challenge with blood tests is that some tumor markers that signify metastatic cancer may show up even when there is no cancer. This means they are nonspecific markers and, therefore, not reliable.
Additionally, imaging tests are used for diagnosis. Some standard diagnostic imaging tests include magnetic resonance imaging (MRI), Computed tomography (CT) scan, and ultrasound.
Treatment of Metastatic Cancer
While treating metastatic cancer, the aim is usually to stop the spread of cancer or slow the growth. The treatment options largely depend on the type of cancer, where it started, its size, and where it metastasized.
However, the treatment options usually undertaken for metastatic cancer are systemic therapy or oral and intravenous medications. Some of these treatments include:
- Chemotherapy
- Hormone therapy
- Immunotherapy
- Radiation therapy
- Surgery
Enrolling in a clinical trial while undergoing metastatic treatment is always an option. Sometimes, the trials are beneficial, especially if other treatment plans have been tried without much positive result.
Wrap Up
Most times, metastatic cancer occurs due to late detection of the primary tumor. When primary cancers are not detected and treated on time, they can spread to other body parts.
Routine checkups can go a long way in preventing metastatic cancer. If you have been treated for cancer in the past, it is advisable that you go for regular check-ups as there are chances of cancer recurrence occurring.
Although there is no definite cure for metastatic cancer, there are drugs that can slow the growth or prevent the spread of cancer cells.