Tumor metastases - symptoms and treatment

Tumor metastases are cancer cells that have spread throughout the body, fixed in one or more internal organs. In 90% of cases, it is metastases that cause the death of a cancer patient 12. Any malignant tumors can metastasize, this is one of the properties that distinguishes them from benign tumors.

Metastasis is now known to be a complex, dynamic process. It plays a role in the mutation load of the tumor (the number of mutations in the genetic code of cancer cells), the interaction between cancer and normal cells, signal molecules that are in the intercellular substance (they interact with cells and control their growth and reproduction).

Probability of developing metastases

Whether metastases occur or not depends on several factors:

• The type of cancer. For example, basalioma metastasizes extremely rapidly, and melanoma refers to highly aggressive neoplasms in which metastases develop very quickly.
• Molecular and genetic features of cancer. For example, triple-negative breast cancer is more likely to metastasize than tumors that have estrogen receptors, progesterone receptors, or are associated with overexpression of the HER2 protein.
• Tumor grade. The higher it is, the more aggressive the cancer and the higher the likelihood of its metastasis.
• Features of localization. For example, breast cancer in the inner quadrant of the breast metastasizes more often than tumors in the lateral quadrants.
• Growth characteristics. Tumors with infiltrative growth metastasize more often and faster than tumors growing superficially. For example, fungal tumors of the colon and stomach are less malignant than infiltrative cancers of these organs.

What affects the rate of spread of metastases

The rate of spread of metastases also depends on the type of cancer, the degree of malignancy of the tumor and its molecular genetic features. For example, high levels of beta TGF protein can increase the rate of spread of metastases.

However, in clinical practice, the rate of spread of metastases throughout the body is more often associated with the type of cancer and its localization. For example, low-grade tumors metastasize earlier than well-differentiated ones, and lung cancer, thanks to a good blood supply, spreads much faster than prostate cancer.

After metastasis has occurred, it becomes very difficult to fight a malignant tumor, this is the last stage in the development of oncological disease. From this point on, treatment is palliative: it helps to slow down the progression of cancer, prolong life and improve the condition, but not cure the patient 3.

Most often, malignant tumors metastasize to the bones, lungs, liver and brain. In some types of cancer, tumor cells spread over the surface of the peritoneum.

The complex chain of events by which a malignant cell breaks off from a maternal tumor, migrates in the body, and forms a secondary lesion in another organ is not fully understood, and work is ongoing in this direction 1. Some theories attempt to explain the causes of metastasis.

One of them says that due to the accumulated mutations, an epithelial-mesenchymal transition occurs: tumor cells begin to resemble those in the body of the embryo and are involved in wound healing. They have an irregular shape, do not stay in a certain place and can migrate in the body.

According to another theory, metastases originate from stem cells, which normally should replace cells that died as a result of damage or naturally. This theory is supported by the fact that tumor and stem cells have a number of common features in structure and biochemical processes.

There is an opinion that macrophages ("devourer cells") help to spread metastases of a malignant tumor, which normally should eliminate foreign particles. In cancer, they support inflammation and angiogenesis (the formation of new blood vessels). This promotes the migration of tumor cells.

In cancer patients, millions of cancer cells enter the bloodstream every day. But only a few of them can give rise to metastases. It depends on the histological type of the tumor (from which tissues it originated), the degree of tumor aggressiveness (cancer stage), cell differentiation (how much they have lost their normal features).