Q: What is the best method of finding breast cancer early?
A: A high-quality mammogram (x-rays of the breast) combined with a clinical breast exam by a health care provider is the most effective way to find breast cancer early.
Mammograms can find tumors that are too small to be felt. The results of several large studies showed that screening mammograms help reduce the number of breast cancer deaths among women aged 40 to 69. The test is especially effective among women aged 50 and older. Research has not shown that it benefits younger women.
The National Cancer Institute (NCI) recommends that all women in their 40s and older have a mammogram every one to two years. Women who are at higher-than-average risk for the disease should talk with their health care provider about when to begin mammograms and how often to have them.
A screening mammogram generally costs between $100 and $150. In most states, health insurance companies must pay all or part of the cost of the test. Medicare pays 80 percent of the cost of an annual screening mammogram for beneficiaries age 40 and older and one baseline mammogram for beneficiaries ages 36 to 39.
Women can get mammograms in breast clinics, hospital radiology departments, mobile vans, private radiology offices, and doctors’ offices.
Call the National Cancer Institute’s Cancer Information Service at 1-800-4-CANCER for more information on breast cancer and how to find Food and Drug Administration-certified mammography facilities.
Q: How do scientists decide which substances to test as possible causes of cancer?
A: Scientists test substances to find out whether they can cause cancer in animals and humans. Thousands of substances could be tested. However, the tests are expensive and take a lot of time. For example, a study on whether a certain chemical can cause cancer in rats may cost several million dollars and take several years to complete. For this reason, not all substances can be tested.
Scientists consider certain factors when they make decisions about which substances to test. Substances likely to be selected include those that affect a large number of people or those to which exposure levels have been very high. For example, pesticides fit both categories. They affect many people because they are used in and around the home and can be found in small amounts in foods. And people in farming communities are exposed to high levels of pesticides.
Naturally, scientists also rely on published reports. This could be a report from a laboratory study showing that a substance can cause human cells to become abnormal. Or it could be a report showing that people exposed to a certain chemical in a particular workplace or geographic area are getting cancer at higher rates than expected.
For more information on substances that have been studied for their cancer-causing effects, read the Report on Carcinogens at the National Toxicology Program Web site at
The National Cancer Institute’s Cancer Information Service (CIS) is one of the country’s most trusted resources. “Ask the CIS” is distributed by the Mid Atlantic CIS, which serves the District of Columbia, Maryland, Virginia and West Virginia. Call the CIS toll-free at 1-800-4-CANCER (1-800-422-6237) between 9 a.m. and 4:30 p.m. Monday through Friday.