While there are many successful treatments today that didn't exist just a couple decades ago, a wholesale " cure for cancer " remains elusive for many reasons. There are more than 100 types of cancer, characterized by abnormal cell growth. There are many different causes, ranging from radiation to chemicals to viruses; an individual has varying degrees of control over exposure to cancer-causing agents.
Cancer cells, and how they grow, remain unpredictable and in some cases mysterious. Even after seemingly effective treatments, crafty cancer cells are able to hide out in some patients and resurface.
About $200 billion has been spent on cancer research since the early 1970s, and the five-year survival rate for all people diagnosed with cancer in the U.S. has risen from about 50 percent in the 1970s to 65 percent today.
Here's a look at the 10 cancers that killed the most people in the United States between 2003 and 2007, the most recent data available, according to the National Cancer Institute (NCI).
1. Lung and bronchial cancer: 792,495 lives
Lung and bronchial cancer is the top killer cancer in the United States. Smoking and use of tobacco products are the major causes of it, and it strikes most often between the ages of 55 and 65, according to the NCI. There are two major types: non-small cell lung cancer, which is the most common, and small cell lung cancer, which spreads more quickly. More than 157,000 people are expected to die of lung and bronchial cancer in 2010.
2. Colon and rectal cancer: 268,783 lives
Colon cancer grows in the tissues of the colon, whereas rectal cancer grows in the last few inches of the large intestine near the anus, according to the National Cancer Institute. Most cases begin as clumps of small, benign cells called polyps that over time become cancerous. Screening is recommended to find the polyps before they become cancerous, according to the Mayo Clinic. Colorectal cancer is expected to kill more than 51,000 people in 2010.
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