The primary purpose of most cancer chemotherapy research, like the work of Elion and George Hitchings, is to keep people alive longer. In this activity students will work with data about cancer deaths. The purpose of the activity is to give students some experience in reading and interpreting graphs, but it is important to remember that cancer chemotherapy is about treating people with compounds that will allow them to live healthy lives.

These graphs present some information about trends in deaths due to cancer in the United States. Study the graphs and answer these questions.

Age adjusted cancer death rates for selected female (left)
and male (right) patients in the United States, 1950-1990. (1,2)

1. How are the two graphs different from each other?

2. Name the variable plotted on the x-axis of the graphs. What is the y variable?

3. What is the range of years included on the graphs?

4. Approximately what was the death rate for U.S. men:
   a. from lung cancer in 1960?
   b. from prostate cancer in 1980?
   c. from stomach cancer in 1990?

5. Approximately what was the death rate for U.S. women:
   a. from lung cancer in 1960?
   b. from breast cancer in 1990?
   c. from stomach cancer in 1990?

6. In which year (approximately) was the death rate highest for:
   a. women from ovarian cancer?
   b. men from stomach cancer?
   c. men from lung cancer?
   d. women from lung cancer?

7. The death rate from which form(s) of cancer increased from 1950 to 1990? The rate for which form(s) decreased in that time period? Give separate answers for men and women.

8. The death rate for which form of cancer increased the most from 1950 to 1990? Which form decreased the most?

9. Can you think of some reasons why deaths from some forms of cancer increased and some decreased from 1950 to 1990? (See “Causes and Risk Factors” below.)

10. What are some reasons that death rates are different for men and women for the same forms of cancer? (See “Causes and Risk Factors” below.)

Interpreting a Graph Worksheet

For a printable version of the See it Now Part 1 worksheet, click here.

Causes and Risk Factors

Scientists are rarely able to identify a single cause for a type of cancer. Cancer is typically the result of a number of events in the human body, each of which must occur for the cancer to manifest itself. The fact that many people who are exposed to known carcinogens never develop cancer reveals that multiple factors are involved.

However, scientists have been able to identify some major risk factors for cancer. Among them are, according to the American Cancer Society:

1. Tobacco: Lung cancer develops in smokers 20 times more often than in nonsmokers. Organs in the pathway of the inhaled smoke (whether from the smokers or those around him or her) are at risk—mouth, pharynx, larynx, esophagus, lungs. Compounds in the smoke also are circulated to other organs like the bladder, kidneys, and pancreas.

2. Alcohol: Alcohol works together with tobacco, increasing the risk of many cancers. It is often termed a co-carcinogen. Heavy drinking leads to changes in the liver, that may increase the risk of liver cancer.

3. Diet: There is evidence to suggest that about one-third of cancer deaths each year are related to diet in some way. Specific dietary factors include high fat, which increases risk for colon and rectal cancer as well as prostate cancer. Fiber—both soluble and insoluble—seems to decrease cancer risks.

   Certain food additives—such as flavoring agents and preservatives—may increase cancer risks. However, the cancer risks of these newer food additives may be much lower than earlier substances involved in preserving foods. Scientists believe that the overall decline in the number of stomach cancers may be due, in part, to people eating foods that rely on refrigerators and newer preservatives to keep them edible over time rather than eating foods preserved through ancient methods such as pickling and curing. Thus, while a substance may have some risk associated with it, it is important to consider these risks against others.

4. Sexual and Reproductive Behavior: Engaging in unprotected sexual contact (that is, without the use of a condom) increases the risk for both men and women for exposure to “HPV”—the human papilloma virus. This group of viruses can cause warts, but much more seriously, can also increase the risk of genital and anal cancers for both men and women.

5. Infectious Agents: There are a range of viruses associated with increased cancer risk. Among them are the hepatitis-B virus, human papilloma virus, the human T-cell virus, and the AIDS virus.

6. Medical Treatments: Ironically, immunosuppressive drugs and some drugs used in chemotherapy may increase the risk for cancer. Estrogen replacements therapy has been associated with cancer of the uterus. Also the effect of diagnostic X-rays and radiation therapy increase the cancer risk.

7. Family Characteristics: A number of common cancers, including breast, colon, ovarian, and uterine cancer recur in generations in families. It should be noted, however, that environmental factors often outweigh family factors.

8. Occupation: Because of possible exposure to known carcinogens, people in some occupations are at greater cancer risk. Some of the industries that pose higher risks of exposure are transportation, chemicals, rubber, shipbuilding, hairdressing and cosmetology, electric equipment manufacture, and health care.

9. Environment: As many as 10,000 people annually develop lung cancer caused by exposure to radon gas. Sunlight, specifically ultraviolet radiation, is a major cause of skin cancer. The American Cancer Society estimates that air, land, and water pollution are liked to about 1% of all cancer deaths.

(adapted from Murphy, Gerald P., Morris, Lois, and Lange, Dianne, eds. Informed Decisions. New York: Viking, 1997, pp 85-92.)