Cancer develops when previously healthy cells in the body accumulate a number of genetic mutations. These mutations allow the cells to begin proliferating out of control while evading cellular death, eventually forming a tumor containing millions of mutant cells. In the late stages of cancer, cells from the tumor begin to circulate throughout the body in the blood vessels or lymphatic system, a process called metastasis, and begin to colonize one or more distant tissues in the body. Although metastatic cancer is advanced and potentially fatal, patients with late-stage cancer may receive a number of cancer therapies.
Systemic Chemotherapy
A common treatment for cancer that has metastasized is systemic chemotherapy. Chemotherapy drugs are cytotoxic agents--chemicals that are toxic to human cells. Over the course of chemotherapy treatment, the drugs circulate throughout the body in the bloodstream and target rapidly dividing cells, such as cancer cells. When exposed to chemotherapy drugs, cancer cells undergo cellular damage and eventually die, treating the tumor. Chemotherapy can damage cancer cells in a number of organs simultaneously. Patients undergoing chemotherapy treatment may suffer from a number of side effects, because chemo drugs also harm healthy proliferating cells in addition to cancer cells. The most common side effects of chemotherapy are nausea, hair loss, fatigue and pain, Medline Plus reports.
Targeted Therapies
Patients with metastatic cancer may also receive targeted therapies. Like chemotherapy drugs, targeted therapies typically travel throughout the bloodstream and can therefore damage and kill cancer cells in a number of tissues at once. Unlike chemo drugs, which target any rapidly proliferating cell, targeted therapies are designed to specifically target cancer cells. Many cancer cells contain specific factors on the surface of the cell that help promote cancer growth, and targeted therapies make use of these factors to identify and kill cancer cells.
One popular targeted therapy is Herceptin, a drug used to treat some forms metastatic breast cancer. Herceptin works by binding to a protein called HER2, which is found in very high levels in some breast cancers. The drug recognizes cancer cells containing HER2, and targets those cells for destruction by the immune system. As a result, the immune system effectively fights off the breast cancer but leaves healthy tissue intact. The use of targeted therapies allows doctors to effectively treat metastatic cancer while minimizing the side effects of cancer treatment.
Radiation Treatment
In some cases, cancer metastases form clusters of tumor growth in certain organs, such as the lungs. Patients with metastatic cancer in the lung may develop breathing difficulties as the clustered cancer growth damages the lungs, and this cancer growth can prove very painful. In these cases, doctors may perform radiation therapy to kill clusters of cancerous growths to slow further lung damage and increase the patient's quality of life, the Fox Chase Cancer Center reports. During radiation therapy, doctors target a high dose of radiation into the cancerous growth, allowing the radiation to severely damage the cancer cells. Following treatment, the cancer cells begin to die, shrinking the tumor and relieving pain. Though an effective cancer treatment, radiation therapy can only damage cancer cells within the region exposed to radiation, and therefore cannot kill cancer cells in multiple distant tissues at once.
