What Is Cancer?
May 13, 2008
Defining Cancer
Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems.
Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start – for example, cancer that begins in the colon is called colon cancer; cancer that begins in basal cells of the skin is called basal cell carcinoma.
Cancer types can be grouped into broader categories. The main categories of cancer include:
- Carcinoma – cancer that begins in the skin or in tissues that line or cover internal organs.
- Sarcoma – cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
- Leukemia – cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
- Lymphoma and myeloma – cancers that begin in the cells of the immune system.
- Central nervous system cancers – cancers that begin in the tissues of the brain and spinal cord.
Origins of Cancer
All cancers begin in cells, the body’s basic unit of life. To understand cancer, it’s helpful to know what happens when normal cells become cancer cells.
The body is made up of many types of cells. These cells grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced with new cells.
However, sometimes this orderly process goes wrong. The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumor.
- Benign tumors aren’t cancerous. They can often be removed, and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body.
- Malignant tumors are cancerous. Cells in these tumors can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis.
Some cancers do not form tumors. For example, leukemia is a cancer of the bone marrow and blood.
Cancer Statistics
A new report from the nation’s leading cancer organizations shows cancer death rates decreased on average 2.1 percent per year from 2002 through 2004, nearly twice the annual decrease of 1.1 percent per year from 1993 through 2002.
Estimated new cases and deaths from cancer in the United States in 2008:
- New cases: 1,437,180 (does not include nonmelanoma skin cancers)
- Deaths: 565,650
NCI’s Cancer Stat Fact Sheets provide frequently requested cancer statistics for a number of cancer types.
What Is a Clinical Trial?
May 13, 2008
Clinical trials are research studies in which people help doctors find ways to improve health and cancer care. Each study tries to answer scientific questions and to find better ways to prevent, diagnose, or treat cancer.
Why are there clinical trials?
A clinical trial is one of the final stages of a long and careful cancer research process. Studies are done with cancer patients to find out whether promising approaches to cancer prevention, diagnosis, and treatment are safe and effective.
What are the different types of clinical trials?
- Treatment trials test new treatments (like a new cancer drug, new approaches to surgery or radiation therapy, new combinations of treatments, or new methods such as gene therapy).
- Prevention trials test new approaches, such as medicines, vitamins, minerals, or other supplements that doctors believe may lower the risk of a certain type of cancer. These trials look for the best way to prevent cancer in people who have never had cancer or to prevent cancer from coming back or a new cancer occuring in people who have already had cancer.
- Screening trials test the best way to find cancer, especially in its early stages.
- Quality of Life trials (also called Supportive Care trials) explore ways to improve comfort and quality of life for cancer patients.
What are the phases of clinical trials?
Most clinical research that involves the testing of a new drug progresses in an orderly series of steps, called phases. This allows researchers to ask and answer questions in a way that results in reliable information about the drug and protects the patients. Most clinical trials are classified into one of three phases:
- Phase I trials: These first studies in people evaluate how a new drug should be given (by mouth, injected into the blood, or injected into the muscle), how often, and what dose is safe. A phase I trial usually enrolls only a small number of patients, sometimes as few as a dozen.
- Phase II trials: A phase II trial continues to test the safety of the drug, and begins to evaluate how well the new drug works. Phase II studies usually focus on a particular type of cancer.
- Phase III trials: These studies test a new drug, a new combination of drugs, or a new surgical procedure in comparison to the current standard. A participant will usually be assigned to the standard group or the new group at random (called randomization). Phase III trials often enroll large numbers of people and may be conducted at many doctors’ offices, clinics, and cancer centers nationwide
In addition, after a treatment has been approved and is being marketed, the drug’s maker may study it further in a phase IV trial. The purpose of phase IV trials is to evaluate the side effects, risks, and benefits of a drug over a longer period of time and in a larger number of people than in phase III clinical trials. Thousands of people are involved in a phase IV trial.
Common Cancer Types
May 10, 2008
The list of common cancer types includes cancers that are diagnosed with the greatest frequency in the United States. Cancer incidence statistics from the American Cancer Society1 and other resources were used to create the list. To qualify as a common cancer, the estimated annual incidence for 2008 had to be 35,000 cases or more.
The most common type of cancer on the list is nonmelanoma skin cancer, with more than 1,000,000 new cases expected in the United States in 2008. Nonmelanoma skin cancers represent about half of all cancers diagnosed in this country.
The cancer on the list with the lowest incidence is thyroid cancer. The estimated number of new cases of thyroid cancer for 2008 is 37,340.
Because colon and rectal cancers are often referred to as “colorectal cancers,” these two cancer types were combined for the list. For 2008, the estimated number of new cases of colon cancer is 108,070, and the estimated number of new cases of rectal cancer is 40,740.
Kidney cancers can be divided into two major groups, renal parenchyma cancers and renal pelvis cancers. Approximately 85 percent of kidney cancers develop in the renal parenchyma,2 and nearly all of these cancers are renal cell cancers. The estimated number of new cases of renal cell cancer for 2008 is 46,232.
Leukemia as a cancer type includes acute lymphoblastic (or lymphoid) leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, chronic myelogenous (or myeloid) leukemia, and other forms of leukemia. It is estimated that more than 44,270 new cases of leukemia will be diagnosed in the United States in 2008, with chronic lymphocytic leukemia being the most common type (approximately 15,110 new cases).
The following table gives the estimated numbers of new cases and deaths for each common cancer type:
| Cancer Type | Estimated New Cases | Estimated Deaths |
| Bladder | 68,810 | 14,100 |
| Breast (Female — Male) | 182,460 — 1,990 | 40,480 — 450 |
| Colon and Rectal (Combined) | 148,810 | 49,960 |
| Endometrial | 40,100 | 7,470 |
| Kidney (Renal Cell) Cancer | 46,232 | 11,059 |
| Leukemia (All) | 44,270 | 21,710 |
| Lung (Including Bronchus) | 215,020 | 161,840 |
| Melanoma | 62,480 | 8,420 |
| Non-Hodgkin Lymphoma | 66,120 | 19,160 |
| Pancreatic | 37,680 | 34,290 |
| Prostate | 186,320 | 28,660 |
| Skin (Nonmelanoma) | >1,000,000 | <1,000 |
| Thyroid | 37,340 | 1,590 |