There are more than 100 types of cancer. Most fall into two categories: sarcomas or carcinomas.
Carcinomas are cancers of the type of tissue that forms skin and the lining of major organs. Eighty percent to 90% of all cancers are carcinomas.
Sarcomas are cancers of the connective tissue, such as bone and cartilage.
Cancer cells differ from normal cells in three main ways: They reproduce faster, migrate to other parts of the body and don't have specialized functions.
A little more than 1 million Americans will be found to have cancer this year. About half a million will die from it.
For all cancers combined, the number of new cases each year increased 10.7% between 1973 and 1985, the latest year for which statistics are available.
The most dramatic increase between 1973 and 1985 was for melanoma of the skin, which increased 60%. Excessive sun exposure is the primary cause.
The greatest decline between 1973 and 1985 was for cervical cancer, which dropped 35%. Early detection and greater use of Pap smears are credited.
Lung cancer is the most common form of cancer in the United States and the major cause of cancer death. Most lung cancer is caused by cigarette smoking. Among women, lung cancer incidence increased 81% between 1973 and 1985. For men, it increased 14.3%.
THE SURVIVAL RATE
The rate of people who survive cancer and are disease-free five years after the diagnosis is now about 50%. Cancers with higher survivability rates are: testis, 90%; colon, 54%, and breast, 74%. Cancers with lower rates are: leukemia, 31%; lung, 13%, and stomach, 16%.
Taking into account hospital costs, the loss of job productivity and the loss of employable years, cancer costs about $72 billion a year in the United States.
Cancer accounts for about 10% of the cost of all disease in the United States.
On average, the person who dies from cancer dies 15 years earlier than his or her normal life expectancy. Lung cancer accounts for a loss of about 1.8 million years of life every year.
THE RECENT BREAKTHROUGHS
The discovery of oncogenes has probably been the most important cancer research discovery in the past two decades. Oncogenes are abnormal genes that appear to be capable of "ordering" a cell to become a cancer cell. Although scientists have identified about 20 human oncogenes, they have yet to unravel the mysteries of the how the "ordering" occurs.
The discovery of substances called anti-oncogenes may prove to be equally important. Anti-oncogenes are substances that somehow "turn off" cancer cells and transform them back to normal cells. (Proteoglycans, the substance that the La Jolla Cancer Research Foundation is working with, is an anti-oncogene.) Research on anti-oncogenes is at an early stage and the potential for use in treatment is unknown.
Much of the recent progress in research can be credited to the discovery of monoclonal antibodies, genetically engineered antibodies that can be created in great quantities in the laboratory. The human immune system creates many kinds of natural antibodies to foreign proteins, such as viruses. Some natural antibodies may neutralize the proteins; others may not. In contrast, monoclonal antibodies are designed to seek out and attack specific proteins. They have become an important tool for isolating and identifying specific cell parts and cell mechanisms. They are used to a limited degree as diagnostic tools. Scientists are also working to couple monoclonal antibodies with cancer-fighting drugs to more effectively target treatment.
Progress has been made with conventional cancer treatments, particularly in the area of chemotherapy. Doctors now know that combinations of certain drugs can effectively treat some types of leukemia that previously would not respond well to any single drug. New methods of delivering anti-cancer drugs also have been developed that have proved more effective. At UC San Diego Cancer Center, an experimental treatment for ovarian cancer has shown promise. It involves administering high concentrations of cancer drugs through an abdominal catheter and applying more directly greater doses of drugs than standard intravenous treatment currently allows
Sources: Figures are taken from the National Cancer Institute's 1988 "Annual Cancer Statistics Review Including Cancer Trends: 1950-1985" and the "NCI Fact Book."