If you have cancer, your doctor may recommend chemotherapy as part of your treatment.
The cells in the body grow and divide as part of the normal cell cycle.
The cell's nucleus controls this process.
Inside each nucleus, genetic material, called DNA, contains the instructions for directing this process.
Sometimes the cell's DNA becomes damaged.
Normally, the DNA responds by either repairing itself, or instructing the cell to die.
In cancer, however, the parts of the cell's DNA that direct cell division become damaged.
When these sections are damaged, the DNA is unable to repair itself, or to cause the cell to die.
Instead, the unrepaired DNA causes the cell to grow and divide uncontrollably into more damaged cells, called cancer cells.
A tumor forms as the cancer cells multiply and displace the normal cells.
As the tumor enlarges, it develops its own blood supply.
Since cancer cells do not stick together as well as normal cells, they may break away and enter a nearby blood vessel.
Cancer cells in blood vessels may travel to other areas of your body and form additional tumors. This is called metastasis.
Additional tumors may form in areas such as the lungs, liver, and bones.
Another way cancer may spread to other areas of your body is through your lymphatic system.
Cancer cells may enter lymph vessels near the tumor, then travel to small glands called lymph nodes.
If the cells pass through the nodes, they may continue to travel through your lymphatic system and form additional tumors.
Chemotherapy drugs work by targeting fast growing and reproducing cells, a characteristic common to cancer cells.
The tumor shrinks as the cells stop dividing and die.
Most chemotherapy drugs work systemically as they travel throughout your body in your bloodstream.
As they circulate, the drugs damage metastatic cancer cells in other organs.
Unfortunately, chemotherapy drugs cannot tell the difference between fast growing normal cells and cancer cells.
As a result, these drugs also damage or irritate some of your fast growing normal cells,
such as those in your bone marrow, digestive system, and hair follicles.
Death, irritation, or damage to these normal cells produces side effects such as
a weakened immune system, nausea, and hair loss.
The goal of chemotherapy is to reduce or eliminate cancer cells in the original tumor, and any sites of metastasis.
In addition to being a primary cancer treatment,
doctors often use chemotherapy as a secondary treatment before, during, or after other primary cancer treatments such as radiation therapy,
or surgical excision of a tumor.
Depending on the location and type of cancer,
you may receive chemotherapy drugs intended to circulate throughout your body, including pills, capsules, or liquids taken orally,
and intravenous or intramuscular injections.
Alternatively, you may receive drugs delivered only to the area of the tumor.
One local method delivers drugs to your bladder or chest through narrow tubes called catheters.
Another local method injects drugs into the cerebrospinal fluid surrounding your brain and spinal cord.
A third local method places slowly dissolving wafers into an area where a tumor was removed.
In most cases, you will receive a number of different chemotherapy drugs to increase their effectiveness.
You may receive many chemotherapy treatments, spread out over a period of weeks or months.
This allows your body to recover between treatments, and to kill as many cancer cells as possible.
Common side effects of chemotherapy include hair loss, nausea, decreased appetite, fatigue, anemia, bruising, and diarrhea.
It is important to rest, eat nutritious foods,
and take medications prescribed by your doctor to reduce or minimize these side effects.