Metastasis is the spread of cancer from its point of origin to another apparently unrelated body site. These cancer deposits are called metastatic deposits (or simply Mets), and such cancer is called metastatic cancer (see Source no. 1).
The name for metastatic cancer remains same as for the original, primary cancer. For instance, breast cancer is metastatic cancer. If it spreads to the lungs, which it often does, the metastatic deposits will be labeled as metastatic breast cancer, instead of lung cancer.
Microscopic examination of metastatic deposits reveals that the cancer cells are identical to original cancer. Moreover, they have similar molecular pattern and proteins as that of primary cancer.
Metastasis usually represents an advancement in the stage of cancer. If cancer has developed its metastatic deposits, rigorous treatment will be required. Only in few cancer types, metastatic cancers can be cured. Unfortunately, most metastatic cancers cannot be treated, despite advancements in cancer care.
Are all tumors metastatic?
No, they are not. You should know the difference between a tumor cancer first before answering this question. Read the article “Is every tumor cancer?”
As for cancers, all cancers become metastatic sooner or later during their clinical course. These include cancer of the blood (leukemia and lymphoma) too (Source no.2).
How does metastasis occur?
Metastasis of cancer involves several steps. These include breaking off of the cancer cells from their primary site, squeezing through the vessels walls, entering into the circulation and finally getting deposited on another site (Source no. 3).
Although the mechanism is a bit complex but thinks of it as a dandelion flower. The flower buds off from its plant, its flower then breaks off and is carried too far off place via air. Similarly, the cancer cells (the flower) break off from primary cancer (the plant) and are carried by the blood (the air) to different sites.
Metastatic deposits are not just delivered via blood to other sites, and lymphatic circulation also plays its part. Lymphatic circulation is the one that clears off wastes from the body tissues.
Where do cancers usually spread?
Although it’s very hard to determine where the Mets for cancer would go without doing proper investigations. But, cancers do spread to some organs in particular. Each cancer type has its preference when it comes to its spread. Here is a list of different cancers and the organs to which they normally spread (Source no 2).
- Ovarian cancer: Lungs, liver, and peritoneum
- Breast cancer: Lungs, bones, liver, and brain.
- Prostatic cancer: Lungs, liver, bones, and adrenal glands.
- Stomach cancer: Peritoneum, lungs, and liver.
- Colorectal cancer: Peritoneum, lungs, and liver.
- Kidney and Adrenal gland cancer: Lungs, liver, and bones
- Lung cancer: Other lung, adrenals, liver, and brain.
- Bladder cancer: Lungs, liver, and bones.
- Skin cancer: Muscles, skin, brain, bones, and lungs.
- Thyroid cancer: Lungs, liver, and bones. Bone, liver, lung
- Pancreatic cancer: Peritoneum, lungs, and liver.
- Uterine cancer: Vagina, liver, bones, and peritoneum.
Can metastasis be identified by symptoms?
In addition to the symptoms of primary cancer, metastatic deposits can develop symptoms of their own too. The symptoms they trigger would depend on their site of invasion, their degree of spread, their size, etc.
If cancer spreads to the bones, it can cause bone pains. Similarly, if cancer spreads to the lungs, it can cause respiratory problems. It depends on the area of the spread of these tumors.
But, metastasis, as already mentioned, cannot just be identified by symptoms. Proper investigations are needed for that purpose.
Is it possible to have metastatic cancer without having primary cancer?
No, it is not possible. Metastatic tumors are always detected after the development of primary cancer.
But, at times, primary tumors cannot be detected, and only Mets are found. It does not mean that primary tumor was never present. In such scenarios, the primary tumor regresses to such a small size that it becomes very difficult to be identified.
What treatment options are there for metastatic cancers?
Metastatic cancers usually represent a very advanced stage of cancer. Quite rigorous and long-term therapy is usually needed to get rid of metastatic deposits.
Multiple treatment modalities are being employed for the treatment of metastatic cancer. These include local therapy, systemic therapy, and alternative therapy.
Local therapy includes the use of radiations or chemicals that specifically focus the targeted site. For instance, radiations might be used to destroy metastatic deposits just in the lungs and nowhere else. The efficacy of this method is usually limited, and this method is usually used when metastasis is not widespread.
For widespread metastasis, systemic therapy is used. It involves giving oral or injectable drugs and full body radiations. This therapy works on a simple principle that the drugs/ radiations given kill all rapidly dividing cells of the body. Since cancer cells are usually very rapidly dividing, these drugs/ radiations usually target those cells and destroy them.
Systemic therapy gives desired outcomes, but at a great price. One major problem with this therapy is that the drugs/ radiations cannot distinguish between normal and abnormal rapidly dividing cells. The cells of our hair, bones, gut, skin, etc. are all rapidly dividing cells. Therefore, systemic therapy has a lot of side effects that limit its efficacy.
But, now research is being done to find new drug agents that target the cancer cells specifically, instead of normal cells.
Another method of the treatment is the use of alternative and complementary therapies. A report showed that use of alternative medicine is becoming popular for the treatment of metastatic cancer. That’s because of its convenience, limited side effects and somewhat better efficacy (Source no. 4).
Metastasis represents an advanced stage of cancer. Once cancer spreads out of its confines, it becomes metastatic. Early diagnosis and proper treatment promise good prognosis.
Sources and references