Video report: Causes of cancer

Anecdotal evidence is of little value when science is searching for something as large as the cause of cancer. Scientists conduct studies over an extended period of time, adhering to rigorous scientific standards. Experts at the National Cancer Institute and National Institutes of Health explain how researchers go about their task, in hopes of identifying triggers for the disease.

About the Author

Truman Lewis
Truman has been a bureau chief and correspondent in D.C., Los Angeles, Phoenix and elsewhere, reporting for radio, television, print and news services, for more than 30 years. Most recently, he has reported extensively on health and consumer issues for and