Metastatic Liver Tumors
What
are metastases?
Metastases are cancer cells that have spread beyond the original (primary)
cancer site and have established themselves at a distant site. These
cancer cells spread through the lymph and vascular (blood vessel) systems
involved with the primary cancer site. Metastases generally indicate
that cancer cells are widespread within the lymphatic and circulatory
systems in the form of "micro metastases", which means that
the cancer is in the process of spreading to many areas.
Determining
treatment options
The staging
system for virtually every primary cancer is unique, identifying the
progress of disease for that particular cancer. The stage of the cancer
determines the treatment choices. For cancer confined to a specific
area, local treatment may be used. Examples of local treatment include
excision (surgical removal), or ablation, which means destroying the
tumor with radiofrequency (high frequency energy), cryosurgery (freezing),
or percutaneous alcohol (alcohol injection), or by blocking the blood
supply to the tumor.
Because
metastatic cancer has spread, local treatment of the primary cancer
will not eliminate the distant sites or the micro metastases that may
be involved in the vascular or lymph systems. The presence of distant
metastases is, in all cancer staging systems, a symptom of the highest
stage of progression. Unfortunately, these high stages are those that
respond least well to treatment and have the worst prognosis.
For metastatic
cancer, it is necessary to use systemic treatments that travel through
the bloodstream and can reach cancer cells throughout the body. Examples
of systemic treatments are biological therapy, chemotherapy, and hormone
therapy. Metastatic tumors, however, may also require local/excisional
treatment if the cancer is accompanied by severe symptoms not resolved
by chemotherapy or radiation. This is often seen with neuroendocrine
tumors.
Are
all liver metastases created equal?
Nearly
any primary tumor site can deposit metastases in the liver, since the
liver filters blood from throughout the body. Most discussions related
to the treatment of metastatic tumors in the liver focus on those originating
from primary colorectal cancer sites. In fact, up to 50% of liver metastases
are of colorectal cancer origin, while the remainder metastasize from
a wide variety of primary cancer sites including sarcomas, breast and
kidney, as well as neuroendocrine tumors.
Since the
liver is generally the first site of metastatic spread, evidence of
metastatic colorectal tumors in the liver does not always mean that
the primary cancer has deposited micro metastases in multiple organs.
Aggressive surgical intervention while the tumors are limited in number
and size and contained within the liver has resulted in reported 25-40%
five-year survival rates. Clinical evidence strongly suggests that as
the metastatic deposits grow in size and quantity, progression beyond
the liver through the circulatory system is inevitable.
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