Top researchers and organizations say progress is being made in the war on cancer, as a new report shows that cancer deaths in the U.S. have been dropping since the 1990's.

The report predicts that by 2020, the death rate could be half of what it was in 2000.

"I think the rate of decline is what is really surprising in this report and actually enormously encouraging," said New York University Cancer Center's Dr. James Speyer.

Among the four biggest cancer killers, new cases are now falling each year.

• Lung cancer is dropping .8 percent a year.

• Breast cancer is down 2 percent a year.

• Prostate cancer is dropping by 2.4 percent a year.

• Colorectal cancer is down 2.5 percent a year.

Researchers believe earlier screenings are making a difference. They also say eating less red meat, less smoking and greater use of aspirin and calcium are helping reduce cancers.