A cancer is a group of abnormal cells, also known as a malignant tumor or malignancy, that grows uncontrollably. Typically, cancerous tumors invade and destroy surrounding tissue.
What is going on in the body?
A chromosome is genetic material within the nucleus of a cell. Chromosomes provide the so-called blueprints that direct normal cell function. The nucleus that houses the chromosomes is the control center for the cell. The nucleus of a normal cell, such as, for instance, a muscle cell, controls its activity as part of a larger tissue, a muscle. The cell will then act in concert with other cells of that muscle to expand and contract, causing motion.
Damage to the nucleus prevents the cell from behaving normally. Cancer occurs when the damage causes the normal control mechanisms in the cell to be lost, with the result that the cell starts to grow and divide wildly. When a cell becomes cancerous, it passes on its abnormalities to all the cells that form when it divides. Thus, over time, a tumor forms from these abnormal cells.
Because the tumor is made up of defective cells, it cannot function as it should. The body suffers in two ways:
A cancer is named by the type of organ tissue from which it developed. For example, breast cancer will always be called breast cancer, even if it spreads to other body parts. The type of tissue within an organ that underwent the cancerous change also further identifies a cancer. For example, lung cancer is grouped into several groups depending on exactly what kind of lung tissue was affected.
A cancerous tumor does not grow any faster than the kind of tissue from which it started. But it does keep growing and multiplying uncontrollably. Healthy tissue does not grow constantly. In the early stages of any cancer, you may not be able to see much of an effect on the body. But cancer cells can break off from the main tumor and travel through your blood stream to other parts of your body. These cancer cells may then form new tumors, known as metastases.
As the cancer grows and spreads, or metastasizes, the person will likely begin to weaken. Cancer makes it difficult for the body to function normally. In the advanced stages of cancer, symptoms such as weight loss, weakness, and fatigue are common. At the same time, new cancerous tumors that spread to other parts of the body may cause other organs to fail. If not successfully treated, the cancer will eventually destroy the functioning of one or more of the vital body systems, leading to death.
These vital body functions include:
breathing, when the lungs are involved
regulation of body functions, when the brain is involved
- waste removal, when the liver or kidneys are involved
Most cancers occur in people older than age 55. This may be because cells become more vulnerable to damage after years of use. There are cancers that are more common in children, but they are much more rare overall than adult cancers. More men than women have cancer. The most common cause of cancer death in men and women is lung cancer.
What are the causes and risks of the disease?
For cancer to occur, something must damage the nucleus of a cell. Some people are born with a tendency for cancer. Their cells may be more vulnerable to the kind of damage that leads to cancer. For others, the damage occurs after years of exposure to substances that can cause cancer. Tobacco from any source is very dangerous. Certain chemicals, unprotected sun exposure, and radiation can all cause serious damage.
What can be done to prevent the disease?
Some cancers can be prevented by avoiding exposure to harmful effects. These include:
Avoiding all tobacco products. Eight major cancers are strongly linked to tobacco use. Lung cancer is the most common of these.
Limiting sun exposure, especially in children, helps prevent melanoma.
Eating a diet high in fiber helps reduce the risk of cancer of the colon.
Avoiding drinking alcohol.
Limiting exposure to organic chemicals used in cleaning or industry, and limiting exposure to radiation, as much as possible.
For some cancers, there is no feasible strategy to prevent the cancer from starting, but it is possible to detect them early. Cancer found while it is still in the early stages is much easier to treat. Thus, one should:
Get regular medical checkups.
(For men) Learn how to do a testicular self-exam and do it on a regular basis.
(For women) Learn how to do a breast self-exam and do it on a regular basis.
Have Pap tests, mammograms, and colon cancer screening performed on a regular basis as recommended by one's healthcare professional.
How is the disease diagnosed?
If cancer is suspected, it must be confirmed by examining the abnormal tissue in the pathology laboratory. This can mean removing a piece of the tissue with a biopsy. Sometimes the whole tumor is removed, which is known as a resection. Additional studies such as special X-rays and blood tests may be done to measure the extent of the disease. This is known as "staging" the cancer.
Long Term Effects
What are the long-term effects of the disease?
Half of all people with cancer are cured with treatment. Fortunately, cancer can often be successfully controlled even if it is not cured. However, if cancer is not successfully treated, it will be fatal.
What are the risks to others?
There is no risk to others from people with cancer. Cancer cannot be spread from one person to another.
What are the treatments for the disease?
Curing or controlling cancer may require that you use many forms of treatment. Some of these are listed below.
Surgery. The first treatment for many cancers is surgery to remove the solid tumor. If the tumor is small enough, the cancer can often be cured this way. This is a local treatment, and it is not effective for cancers that have spread to other parts of the body. Leukemias and lymphomas are not localized because they affect cells that circulate throughout the body in the bloodstream. Therefore, they cannot be treated by surgery.
Chemotherapy. This is a type of treatment that involves the use of medicines. The healthcare professional gives these medicines to you either by mouth or directly into a vein. Next, they travel through your body via your blood. This is called a systemic treatment because the medicines may affect your whole body. This approach has been used to cure or control cancers such as leukemia that are more widespread than local.
Chemotherapy may also be used for cancers that began as a local tumor, but have now spread to other parts of your body. Just as some infections do not respond to antibiotics, not all cancers respond to chemotherapy. Although chemotherapy drugs are more toxic to cancer cells than to normal cells, because the cancer cells are actively dividing and growing, chemotherapy typically damages normal tissue enough to make an individual ill.
Radiation. In this local treatment, focused energy waves (x-rays) or particles (electrons and other atom particles) of radiation are directed at tumors. These can kill or slow the growth of many cancers. Cancers that are localized and sensitive to radiation may even be cured by this treatment.
Examples of cancers that can be cured by radiation are Hodgkin disease and cancer of the voice box (larynx), prostate and cervix. Radiation therapy is also used to decrease the risk of recurrence of tumor following surgery.
Immunotherapy. This form of treatment uses the body's immune response to kill or control the cancer, for instance, by injecting a specific antibody that will latch onto tumor cells and make them targets for the body's immune cells. Immunotherapy has limited effectiveness and is useful only for certain cancers. Many cancers are too advanced at diagnosis to be affected by this approach alone. In many cases, a combination of treatments has proven most effective.
What are the side effects of the treatments?
The side effects depend on the type of treatment and the extent of treatment.
- Extensive surgery or intensive chemotherapy may require a long recovery period. Current management of side effects make it possible for many people to maintain normal activities throughout the treatment period.
- Localized therapy may have minimal side effects.
- In advanced cancer, treatment is aimed at improving quality of life and decreasing symptoms of the cancer.
What happens after treatment for the disease?
After treatment, the person with cancer will be watched closely to determine the effectiveness of treatment. People who are cured of their cancers should be able to resume normal lives. If the treatment is not effective, other therapy may be tried. If all therapy has proved ineffective, every effort will be made to assure comfort during the final stages.
How is the disease monitored?
Each cancer is followed according to type and how it was diagnosed. Leukemia is followed by examining blood samples. Lung cancer is followed with special X-rays of the chest. Progression of an advancing cancer may be monitored through X-rays, CT scans, or MRI scans, depending where the cancer is known or suspected to have spread. Any new or worsening symptoms should be reported to the healthcare professional.
Yarbro, C.H.(Ed.)(1997). Fundamentals in Oncology, Part 1. Bristol-Myers Squibb Company: Princeton, New Jersey. Pp. 1-92. 1/26/00 slr