Americans could realistically cut the death rate in half, the report says. This year 1.368 million Americans will learn they have cancer and 563,700 will die of it.

"The American Cancer Society estimates that in 2005, more than 168,140 cancer deaths will be caused by tobacco use alone," the organization said in a statement.

"In addition, scientists estimate that approximately one third (190,090) of the 570,280 cancer deaths expected to occur in 2005 will be related to poor nutrition, physical inactivity, overweight, obesity and other lifestyle factors."

That totals 358,230, or 62 percent, of all cancer deaths.

"The issue is how many could you actually pull off in reality and half doesn't seem like a big stretch," Dr. Michael Thun, head of epidemiology for the non-profit group, said in an interview.

"If one could eliminate tobacco use, you would eliminate about half of cancer deaths. If you could help people maintain a healthy body weight and get more physical activity, that would be another 10 percent," he added.

"Increasing colorectal screening and high quality mammography and Pap (tests for cervical cancer) would contribute another fraction. It is very plausible that one could get a 50-percent reduction."

For instance, breast cancer, which kills 40,000 women and men in the United States every year, can usually be easily treated if caught before it spreads. In February a team at Harvard Medical School calculated that if every woman aged between 50 and 79 got a mammogram every year, it would reduce deaths from breast cancer by 37 percent.

Colon cancer and prostate cancer, two other top cancer killers, are also easily detected early with proper screening.