A diagnosis of metastatic cancer refers to cancer that has spread (metastasized) from the place where it originally started (primary site) to another place in the body. The tumor formed by these cancer cells is called a metastatic tumor or a metastasis, and has the same name as the original cancer. For example, when breast cancer spreads to the lung, that new tumor is called a metastatic breast cancer, not lung cancer.
About Metastatic Cancer Cells
Metastatic cancer has the same type of cancer cells as the original tumor. These cells generally look the same as cells of the original cancer, and usually have some molecular features in common, such as the expression of certain proteins or the presence of specific chromosome changes. But since they may not be exactly the same as the original tumors, they may be harder to treat.
Virtually all cancers, including cancers of the blood and the lymphatic system (leukemia, multiple myeloma and lymphoma), can form metastatic tumors. The most common sites of cancer metastasis are, in alphabetical order, the bone, liver and lung.
However, the ability of a cancer cell to metastasize depends on several factors:
- The cell’s individual properties
- The properties of the noncancerous cells, including immune system cells, present at the original location
- The properties of the cells it encounters in the lymphatic system or the bloodstream and at the final destination in another part of the body.
Not all cancer cells, by themselves, have the ability to metastasize. In addition, the noncancerous cells at the original location may be able to block cancer cell metastasis. Furthermore, successfully reaching another location in the body does not guarantee that a metastatic tumor will form. Metastatic cancer cells can lie dormant (not grow) at a distant site for many years before they begin to grow again, if at all.
How Cancer Cells Spread
The spread of the cells usually follows a pattern.
- Cancer cells invade nearby normal tissue (local invasion).
- Cancer cells invade and move through the walls of nearby lymph vessels or blood vessels (intravasation).
- Cancer cells move through the lymphatic system and the bloodstream to other parts of the body (circulation).
At this stage, the cancer cells in small blood vessels called capillaries stop moving and start migrating into the surrounding tissue (extravasation). They then proliferate or multiply at the new location to form small tumors called micrometastases. These tumors stimulate the growth of new blood vessels, which gives the new tumor the oxygen and nutrients to continue to grow.
Whether or not cancer cells have metastasized is also helps determine the stage of the cancer. The TNM classification system for cancer encompasses three classifications that enable the tumor staging to be determined:
- T for primary tumor size
- N for lymph node involvement and extent
- M for absence or presence of distant metastases
A tumor classified as T1, N0, M0 cancer (small tumor, no nodal involvement, no distant metastasis) is considered a stage I tumor, while one that is relatively large, has spread to the regional lymph nodes and metastasized to distant sites in the body would be classified as Stage IV.
“Patients facing metastatic cancer are not alone. Patients with metastatic cancer have a comprehensive team of oncology specialists providing support throughout their journey and, in addition, new advances in treatment of physical symptoms support improved quality of life and clinical trials also offer new advances,” said Emily Gentry, Division Manager, Oncology for HCA North Texas, a Sarah Cannon network of excellence member. “Every patient responds differently to treatment and patients with metastatic disease can make choices to pursue the most individualized treatment plan available for them. Fortunately, cancer researchers continue to introduce new treatment options for patients.”
About Treatment Options
Treatment for metastatic cancer generally depends on the type of primary cancer; the size, location and number of metastatic tumors; the patient’s age and general health; and the types of treatment the patient has undergone previously. Options include systemic therapy (chemotherapy, biological therapy, targeted therapy, hormonal therapy), local therapy (surgery, radiation therapy) or a combination of these treatments.
Researchers are looking not only at new treatment methods to kill or slow down the primary and metastatic tumors, but also ways to disrupt individual steps in the metastatic process.